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  1. 123 points
    My retired colleague Ian McCaskill, RIP, would have relished discussing this Christmas Kerfuffle on-air with typical humour. GFS 12z deterministic very similar in final reaches of run to Thursdays ECMWF Monthly broadscale set-up for same period just after Christmas. Whether that will remain so tonight, we shall see....
  2. 105 points
    If I may interject here... It might be worth you going back and reading the posts that have been made, and represent what was actually said vs what is happening - and not spurious interpretations of words you choose to put into mine, and others mouths please. There have been several reviews. Indeed, the last one I made was barely 48 hrs previously on Wednesday! They are very easy to find on one's activity page. But as you admitted recently - you don't read many posts (beyond trumpeting your own) other than the ones you feel the need to 'challenge' as part of your compulsion for one-upmanship A pattern change from highly +ve AO was muted two weeks back of an Atlantic ridge vs Scandinavian trough (along with my usual 'waffle' of reasoning and explanations) At this time, however, you were customarily oscillating between the highs and lows of intra model day output - and fighting the corner of the Russian High, which never had any support to back westwards a cold pattern. Duly, we have arrived at that scenario of Atlantic ridge and Scandinavian trough - and also an upstream sub tropical jet - a sequence which was anticipated through watching the the expected movements of the Global Wind Oscillation through an extreme high amplitude Phases 5-6-7. They are too long and tedious for you I know, but you could go back and read the posts for yourself. I do believe that is exactly where we are - and what is playing out still in the modelling through this week. I have, for what it is worth, personally stayed clear of all the erratic and incoherent operational output and also taken a distrust to ensemble data in the last day or so, such is the chaotic nature of the pattern - and especially with the bonus addition of a January Atlantic tropical storm thrown into the mix as well! Attraversiamo... Going back to the posts and the reality vs the misrepresentation. I posted about 10 days back as the arrival of the upcoming amplified pattern came into focus that we might look to a loosely based comparison (as difficult as it is to do this in terms of the uniqueness of this 15/16 Nino event) of the Nino forcing that evolved in the Pacific through the 82/83 winter. Not meant to be taken as a literal meaning that the day by day synoptics will replicate identically, because of course they won't, but as a theme to watch. On that basis, and in terms of the way a highly ramped up atmospheric angular momentum framework has been working in tandem with changes over the polar field to a much more destabilised vortex arrangement, and hence making a highly significant difference to the first half of winter - we might see the NH pattern replicate a similar evolution from Jan > Feb 83. Frankly, and with some time also yet to pass, I see no reason whatsoever to dispute that at this time. Especially as many of the longer range tools and seasonal modelling are indeed now pointing to such an amplified pattern occurring as a theme in the remainder of the winter. As the associated feedbacks that have created these grow, the chances of link-up to the heights over the NE increase - and here parallels with Feb 83 increase further as those charts from the first/second week of Feb imply in the archives Stewart clearly had this analogue in mind himself ( and as part of his obviously more experienced thinking than mine) gave his own very similar rationale behind the tropical and extra tropical forcings that were moving the pattern onwards and he suggested the template from the 17th Jan to approx (I think from memory) 8th Feb for continued development of the theme of change away from the anomalously warm +ve AO theme of the first half of the winter to one that features recurrence of the very theme we see now of amplified Atlantic ridge and Scandi trough. But - with time, this embedding in place in such a way as to increase the likelihood of the southern stream undercutting and backing the cold air to out N and NE further and further towards us the more time moved on. If you look further up this page, I do believe Stewart has updated his thoughts to suggest exactly this development , and further to a post he also made on Wednesday. There is no clearly requirement for me to add further to that latest post, as based on following many same data sources I inevitably come to conclusions that concur. There are many highly informative and knowledgeable people to learn from on this forum - and in addition to those various members, I will happily and freely admit I have attempted to learn from studying and interpreting in NWP model output the same GSDM framework Stewart has been an expert on for so long. People are free to disagree with these methods, and whilst none of us can control the weather and claim to have unique powers of perception to oversee every development, over the course of the last 18 months I have come to fully value the worth of intra seasonal and sub seasonal phenomena in providing insight into how NWP modelling may evolve. Last winter, for me was a great starting point to put these into practice - and which I found hugely rewarding. I would much rather follow such a constructive method of research and learning, and making mistakes along the way as means of improvement, than seeking to undermine others as some bogus means to earn an imaginary competitive forecasting prize at the end of it. That is not the same as having different opinions and respectfully discussing them
  3. 103 points
    ??????? Eh? The next 7 to poss more days are signalled as below average!! The next 2 nights look firmly set to be coldest of this autumn!! I suspect there's people so obsessed with snow forecasts that they're not seeing wood for the trees. No cold: no snow. And as I posted above, usual suspects in media aside, nobody sensible has given a snow prognosis 10+ days ahead... because the forecasting science to do so with any reliability doesn't exist. Honestly, compared to some recent winters(!), I fail to see anything in longer range models to make cold lovers moan.
  4. 103 points
    Reasons to keep perspective: 1) In real time modelling we are right here, right now, turning a massive corner from the blowtorch/rainfest regime of the late autumn and early winter. We have seen the worst of the 90's +AO Nino regime, as referred to in early season posts, and are now staring at the barrel of a 60's to 80's type -AO Nino pattern. Lorenzo, in his own way, discussed the sheer scale of all this in his overnight post - and it really cannot be over emphasised. On that basis, as a weather and weather pattern enthusiast, despite the unpalatable weather at the surface witnessed up to this change, the lead up since summer 2015 into the early part of this winter has been the most rewarding study/observation possible. 2) We can trust that this fervently primed atmospheric circulation, as a seasonal dog of two heads, is set to show what its -AO alter ego can do. In this respect some patience is required while the NAO mode completes a transition to fully connect with the change of regime over the pole. Its not quite there yet. Trust the seasonal wavelengths here the more we head through the month to February, and especially trust what is happening, and is set to further happen, upstream in the Pacific and 'elsewhere' (other posts have covered detail, no further repetition required). 3) We knew before the NWP modelling really ratcheted up a gear through yesterday in terms of the tanking polar and amplified Atlantic profile that another sub tropical jet streak was in the offing circa the 10 day period. And, being early in the overall Annular Modal transition as described here, and in recent posts ( and with some 'latent heat' left especially in the surrounding seas) that an initial tendency towards a west based NAO regime (as the first part of modal transition) might suggest some initial cut-off cold advection scenarios where residual troughing phases with the upcoming jet streak out of the SE USA. However, we cannot be sure yet to what extent, if much at all, this might delay cold air advection fully south. Tbh though, with the trend being a friend, none of this actually matters to me at all at the moment. I'm not absorbing myself too much in intra output details. We are all free to approach the model output in any way we choose of course. I am simply suggesting not to be too unduly ph(azed) and fret over it. 4) Right now, as written yesterday, I think we are seeing the first stage of a lock down (in terms of the change of pattern) that will evolve a new cold regime potentially becoming colder still as we head towards and especially into Feb (in terms of a further cold spell then). Each new daily set of data is re-enforcing this in my mind. Taking the situation in the here and now, and what it is to come - there is more poleward amplification in the circulatory system to shake a stick at. With the polar field drastically changing, we must keep remembering this and have some trust in it. 5) Most all our main cold spells are interspersed with less cold blips - this applied most recently in Dec/Jan 10 (in the south) and also there was a pause during the exceptional late November/December 10 spell. But going back through weather history the list is endless anyway. This is the UK and not Siberia or Northern Canada. In this sense go back to the first item on the perspective list. and see where we have starting to move away from. I've been enjoying the atmosphere tug of war immensely anyway, and then as a adoring fan of snow, like many of us, am trusting in the pattern that is unfolding, I feel I can afford to wait till it arrives outside my window because anticipation is growing for next 6 weeks. The weather will have the final say of course, but I am happy to be very glass full at this time @BFTP : I think that there are good reasons, as outlined in recent posts, for a further cold period in February, and, with less issue regarding any possible west based -ve NAO, and H500 anomalies adjusted slightly further east, quite likely would be colder still than the upcoming one. 'Lock down' is intended to refer to an overall regime change from the first half of winter, not necessarily literally a whole month in the freezer! No-one can predict anything like that
  5. 102 points
    ECMWF Monthly goes off-piste versus it's deterministic brother into & particularly beyond Christmas. The +ve GPH/MSLP anomalies out to our NE merely intensify again towards end of month, then show signs of retrogressing 1st week Jan to lie directly to our North, with mean E flow trending more E-NE with time. Glosea likes the idea of a more blocky Jan too... but the term 'deja vu' springs to mind! Other shenanigans aside, at least Glosea strat diagnostics have been sound last few weeks, so given emergent January signals the PV may yet yield a 'surprise from aloft'. We shall see.
  6. 102 points
    EC Monthly consistent with Glosea and it's last runs. Strong resurgence of +ve MSLP/GPH anomalies north of UK further into Dec, especially Xmas week, with marked -ve temp anomalies developing across adjacent contiguous Europe as N'ly flow veers to mean easterly late Dec. Good to see both suites in such firm agreement, despite inherent issues of confidence at such lead time.
  7. 98 points
    That's a good tee up for this.. From a subseasonal and seasonal perspective, the gift that has kept on giving is the pattern over the Maritime Continent. I've used this a lot (to success) over the mid summer and autumn periods as a key driver influencing the hemispheric pattern. It was an excellent lead for the high pressure signal centred over Europe and troughing in the Atlantic. Through September and October, this pattern has remained an only recently has it diverged. This is really useful in understanding why we are getting divergence in the pattern, and key to understanding if or more appropriately when it will return as the key driver. So what am I discussing here ? Well, let's look at the spatial arrangement of sea temperatures across the Indian Ocean and West Pacific. There's a text book signature for enhanced low level westerly winds through the Indian Ocean and easterly winds through the central Pacific. This is evident in surface wind anomalies for the region. Where winds converge, upward movement of anomalously warm air leads to convective activity and again this footprint is evident in rainfall anomalies. What's crucial here is that this convective pattern is mirrored in the upper and mid troposheric levels. Here we see an enhanced (negative) velocity potential associated with a substantive standing wave. Analogues for this provide a clue as to how September - October should have looked.. Compared to observed.. That's actually not a bad match across the Northern hemisphere, allowing for a more blocky type pattern over the Arctic related to other drivers, and particularly within the Atlantic sector. So we have a useful blueprint as to how November and December should pan out, given the likely persistence of the underlying driver, the spatial arrangement of SSTAs in the Indian Ocean and Maritime Continent. However, in the last week we've seen the modelling develop a deviation from this pattern. Why ? The answer to me lies in destructive interference from an emerging MJO wave. GEFS and EC EPS are consistent on the development of a convectively coupled wave moving through the central Pacific and Western Hemisphere (phases 7-8-1). Composite for these phases, and you'll understand why we're seeing the trough signal over NW Europe. Note the development of higher than normal heights over Easter Europe and Western Russia there. That is the perfect geoeffective position for upward wave reflection into the stratosphere. Is that part of the beautiful choreography of the atmosphere to bring about a stratospheric warming end November / early Dec ? So assuming the MJO is a player, where do we go from here ? A stall in the MJO in phases 7 or 8 is unlikely. It rarely gets stuck there. Where it does sometimes linger is the Indian Ocean, phases 1, 2 and 3. This seems unlikely in terms of what we've seen and underlying sea temperatures in the region. That leaves me with a likely return of the convective wave quickly to the Maritime Continent as per GEFS. That may well enhance or excite the standing wave once more. Analogues for this for November / December show a very coherent signal for +ve height anomalies in the mid Atlantic, to which you would need to adjust for greater amplification on the back of zonal wind anomalies (weaker than normal) and warming of the column around Barents Sea. If the GEFS is correct here, we should see a return to the mid Atlantic ridge or even blocking further north in the medium to long range. I would expect to see a Scandinavian trough also emerge. This will be tied into the evolution of the MJO towards phases 4 and 5. One further line of thought is relevant here. As others have keenly observed angular momentum remains disconnected from the ENSO state. For a weak La Nina, we should be seeing -1SD, not +1SD. This is reflective of an atmosphere which is primed for amplification. If the MJO swiftly propagates eastward and enhances the convective / upper level velocity potential over the Maritime Continent, we should see a corresponding upward spike in tendency in relative angular momentum giving a large projection of the GWO towards phase 4. Analogues for this with a ten day lag applied are interesting.. So for the next 10 days or so, cyclonic and troughy over NW Europe, temps not far off average or above. Thereafter, would expect to see a transition to a more blocky type pattern with height rises in the mid Atlantic and points north over time.
  8. 97 points
    Temperatures are about to start a decline to below average and expectations are for quite a few weeks of that situation remaining, with cold/bocked weather dominating. It could last well into March. Longer range products have only just started reacting to the MJO phase 7 (which tends to have instantaneous response in outcome here) due to lag. Now we can see the direction becoming clearer in GloSea5 and EC Monthly, we await the operational model centres to catch-up. Storm track is expected to become ever more southerly in next 1-3 weeks, with inherent prospect of these passing to S-E of UK and resultant risk of wintry hazards. It's total chalk and cheese change versus winter so far and evidence is now compelling for most protracted period of below-normal temperatures seen for some time. It matches exactly the UKMO Seasonal Team assessment for this winter, but only now is the model evidence becoming well aligned.
  9. 95 points
    EC week 4, let's just say, what price a white christmas ? Genuine -ve temp signal there at that range is stark. Week 3 continues the theme as discussed, cross polar ridging.
  10. 92 points
    Evening All For those of us who have been here for a long while there is times when you know you have to throw in the towel on chasing cold & times ( very rare ) when you 'just know' that the Cold solution is correct - Today is one of those rare occasions ( last seen nearly 4 years ago ) when what I see developing in the models & more importantly 'how' its developing gives me near 100% confidence that we will see things panning out close to the ECM - Lets recollect the last time this happened & pick these 4 days you will note the start date of the trough dropping south is 13 Jan 2013 The UKMO 4 days before http://www.meteociel.com/modeles/ukmo2.php?jour=9&mois=1&annee=2013&heure=12&archive=1&mode=&ech=72&map=&nh=0&carte=1021 The ECM 4 days before http://www.meteociel.com/modeles/ecmwf.php?jour=9&mois=1&annee=2013&heure=12&archive=1&mode=1&ech=72&map=0&type=0 & the GFS 4 days before http://www.meteociel.fr/modeles/gfse_cartes.php?jour=9&mois=1&annee=2013&heure=12&archive=1&mode=0&ech=6&runpara=0&carte=0 If you run each model through you see the clear issues that GFS has which is eastward bias & not splitting energy .. Today we find ourselves in the same boat- GFS not splitting energy & moving the whole lot eastward- it will take the GFS 24/36 hours to catch up- Its also worth noting why the seasoned campaigners on here show 'little' interest in the ENS means - Assuming the ECM OP is close for day 6 with the ' wedge ' - ( ignore the shortwave flow ) look at yesterdays Day 6 ENS means - very poor from GFS ECM 00z poor 12z ECM 'trending' So those posting Means charts day 8/10/12 - even 16 look so foolish so often ... The only thing to do is reviewing trending... Anyway- sound the alarms - The train has left the station & its on its way !!!! - just follow the evolution from this- http://www.meteociel.fr/modeles/archives/archives.php?day=9&month=1&hour=0&year=2013&map=0&region=&mode=2&type=ncep Moving Over to the strat - The warming that Many of us have been forecasting / following over the last 10 days is now coming to fruition & the initial prognosis of a double dip drop in zonal winds looks to be the form horse ( as opposed to the straight plummet to negative ) The zonal wind @10HPA Over 60N is now is a state of freefall - peak value just 5 days ago was an elevated 48 M/S ( climo for late jan is 30 M/S ) - we will reach the climo line tomorrow & the 20 M/S line 2 days later indicating the deceleration curve is about 5M/S per day - So before the short projected stalling of the first dip the minima will be in 5 days around 18 M/S - There is around 95% agreement ensemble agreement - Post that there is a solid 50/50 split in the warming & deceleration becoming an 'official' SSW with the wind going negative Seen here This is why the albany site forecast doesnt get below zero because its the mean - when in reality its a 50/50 chance with ob iously the lower the better numbers.. What I personally believe about whats happened today in the models - is through high entropy the ECM has resolved the tropospheric response quicker than the GFS -& just highlight This is NOT MJO related for anyone who says it is as its still sat in COD - If you want further proof of the fact that its a tropo response then look no further than the zonal wind data @60N for the dates above - The wedge developed on the 10th of Jan 2013 - This is the merra data Look close the 15M/S day was the 5th, the wedge was there on the 11/12th - see below The was also some pacific response as well - now look at the temps & locations... So in summary: This is 2013 revisited- with 'hopefully' deliver a similar outcome in the short term quick troposheric response as well as the 40-50 day AO profile that encompassed March 13 record breaking -AO as well ( we do probably need the Full SSW to deliver that ) best S
  11. 92 points
    So to repeat what I just added over on TWO bin all the GFS & ECM suites go with a total pattern change in the next 12-24 hours to a very cold easterly at 144-168 quote - Appologies for any spelling- tapping on phone Just to add to me comment from earlier as I have half hour - I can assure everyone I wouldnt just post & comment If I didnt believe it would have a strong probability of happening- I have been saying the same for days on NW but maybe not as clear & as loud - As it stands there is no ensemble support ( less than 10%) for what im saying but im drawing on what ive seen over the last 14 years - watching every run ( winter ) of the AVN > GFS UKMO & ECM right back to the old snowatch days - I guess in those 14 years the amount of runs modelling scandi / Russian highs delivering deep cold to say debilt at 120-144 have been averaged about 2/3 a year ( obviously thats all the runs for 1 outcome grouped together each time ) & of those 40 odd scenarios the deep cold has penetated to the UK probably a third of those occasions - my memory highlights Feb 2005 , Feb 2009 , dec 10, jan 13- Mar 13 ( rem the undercutter ) but of course some more - also the pain of many failures- I would also add that across those 40 scenarios as a rule of thumb the AVN / GFS is as useless as they come - & to top that the GFS ensembles are the cherry on the useless cake - The ECM has performed well - however its lost some of its kudos in recent years - The UKMO has been pretty consistent but of course has occasionally got it wrong- I would like to think I know where to look when seeing these models & what their weaknesses are - GFS never seems to model the scandi blocking well but also its secondary weakness is not having the resolution to seperate parcels of energy ( PVA ) So when you have a scandi block & are reliant on the models deciphering how much energy is seperated & heads SE so the GFS is at its weakest - it will always move the jet through the block at a NE angle until it gets to grip with the real solution - this often arrives rapidly in the 96-120 arena on operationals & usually a day later on the ensembles - so the integrity of the GFS suite today at 144-168 is pretty flakey. The NE angle of attack is then replaced with a SE angle of attack - The euros will be much more realistic & should be prone to less swings ( again ECM has been showing occasional inter run volality since the upgrade - ) Its also become more apparent to me that theres ALWAYS a trend in the days modelling - sometimes its blindingly obvious - sometimes more subtle- I look for these trends in the places that will impact the Uk in the following days - so thats not overhead -& in this scenario its the development & angle of the dreaded shortwaves coming around the high over russia - to the angle of the waves exiting the coast of the US- These nuances & changes at say 72-96 are the ones that have the 'big' impacts on the pattern at 144-168 I find this far more interesting than chasing future possible teleconnection changes as they are far more specific to the UK- which in my view is of course more important - Anyway- We are at the exact point today where a CRITICAL element of the resolution of the energy distribution will have large scale impacts on the pattern feeding Europe ( NW ) including the UK at 144-168 The models for probably 4-5 days have had the MAIN low arriving at 120 stalling out somewhere close to the NW of the UK allowing energy underneath to be sufficient to keep the deep cold east past Debilt- They havent allowed any lows to 'turn over' & advect the cold back west... ECM & GFS 00z both support this scenario by developing a wave off the gulf at around 84-90 which aubsequently gets swept up in the eastward jet ( flat no amplification ) this wave then comes under the parent low at 144 & slides across southern england giving a very brief continental flow on its Northern flank - (ECM 00z + GFS 00z) However as the flow behind it sees additional phasing of low pressures in the atlantic & the subsequent development of the deep circular low - it all sweeps east with ease- Goodbye block-:( Also to the NE towards Norway the models have placed another shortwave with low heights there traversing WNW- this again stops the block forcing ESE towards the UK. So in isolation - theres just 2 shortwave features both conspiring against the UK for cold... But what if the trend of the day was to change the modelling of these in terms of positions? Well then the longwave pattern will follow- Its my proposal that as we reach 72-96 the models will resolve the heights over Norway & across to iceland & as a result will display heigher heights that originally predicted - Vis a vee the Cold air advection heading westward out of the continent will have more directional forcing WSW not WNW Now to address the atlantic profile - The initial deterministic resolution shows a flat jet with one wave exiting the US on a trajectory with the south of the UK under the parent low, but what if the models are going to react to the downstream changes of heigher heights over Norway with upstream teleconnective changes of more accute amplification - IE creating a ridge with perhaps 2 areas of energy exiting the states - If this happens & you throw a ridge in there then you get an inflection point - the sharper the ridge the sharper the inflection point- All of sudden the wave heading for the UK becomes very very shallow & recurves south towards spain & portugal .... Whilst the other area of energy - again becoming more defined & deeper as it traverses a steeper thermal gradient into the lobe of the vortex goes NORTH west of the big low over the Uk- The net of the this is all of a sudden theres energy heading south to portugal as well as a ridge building over the top of our UK low - forcing it south ( not back NW as the GFS keeps doing ) Bonus wise here is the fact that there no immediate energy against the block over southern england - We then allow the CAA to burst west into the UK ( as long as the low exits southern england & doesnt stall ) If it stalls in the south then its just te North that benefits from the Easterly flow. So these 2 key events - if they are the trends of the day & what ive seen the atlantic ridge has shown on the * UKMO 00z * GFS 06z ( not acute enough ) * JMA 06z t84 has the ridge * APERGE 06z t72 has a ridge forming.. I would expect a significantly different suite tonight in favour of cold. Its happened before - I have called that before ( but of course I have also not been right ) Take it or leave it S
  12. 91 points
    Evening Guys - Well its been an utter rubbish day on the model front- last nights call was based on the european models- more especially the ECM displaying the exact scenario & evolution it did in 2013 & the UKMO had joined the party on the 00z ( tues ) but did move away yesterday 12z- The GFS was to flat to start with & the ECM even at 120 was to amplified- the median point yet again coming out with another stella performance was the UKMO - I cannot praise this mode high enough this year- every single cold spell that hasnt varified- which has been most if not nearly all- The UKMO has never really been on board & perhaps I should have waited till 00z today to post- However when the data is almost identical from the yesteryear right down to the zonal mean dropping again- almost identical to 2013 then it seemed a no brainer. so yep the call was wrong... it may interest a few that this year Im going to work on a new teleconnection, ive not named it yet however it will be based on 2 specific weather patterns that deliver cold for the UK & within that the leads up focussing on MJO data & Strat data - for example, since 1979 there have have probably been around 15 -20 greenland highs - it will be interesting to see my results of what the zonal mean was when these developed, especially in non SSW years - have we had any GHs in non SSW years... Anyway - enjoy your eves -- im as frustrated as anyone ... S
  13. 89 points
    Another day and another 24 hrs of model watching. Pub was just about to close last night and we had a few big hitters GP, Fergie etc basically said drinks are on the house. “”12z ECMWF ENS set against model climatology lean pretty firmly in median 2m temps towards below avg (at times quite markedly) out to at least 9 Dec. “” “”.and a big intrusion if the N Pacific ridge into the Arctic towards the mid Atlantic ridge. Strongly negative AO latter stages of the EPS”” Tamara adds a few cheeky Christmas charts and it’s a lock in. Someone talks about previous T240 charts not verifying but soon gets drowned out. The curtains are raised at 10pm as we get’’’’’’’…EC Monthly consistent with Glosea Strong resurgence of +ve MSLP/GPH anomalies north of UK further into Dec, especially Xmas week, with marked -ve temp anomalies , Bets are taken on a white Christmas This morning Today's outputs all point to the same trend in terms of some increase in amplification upstream and more digging south of troughing in the Atlantic but early differences mean the weather for the UK could be either a spell of milder sw'erlies or staying cold 06z following the 00z so far with the high sinking south allowing south westerlies to come in though not in a reliable time frame by any means. That’s south westerlies mentioned twice , they better stay outside of the reliable time frame toss*** No real changes in the outputs with the GFS still showing the threat of mild SWlies and the models in general showing a high pressure dominated outlook. Ok that’s enough south westerlies aint going to be a buzz word, If high to drift towards the east and we pick up a SE'ly . To be fair the 06z gets closer to the ukmo output between 120 and 144 hours compared to the 00z by shoving the high more over the uk!but goes default and push everything eastwards after that!! The high says make up your f****** mind where am I going ?? Post T144 the GFS 6z doesn’t want to get rid of that SW direction. Into the afternoon The London 00z ens temperatures post 6/12 show more spread then a tub of lard. GFS is all about the shortwave spoilers. Welcome back short waves , make sure you go in the right direction There is a great degree of divergence between ECM and GFS ensembles ,reflecting how the UK high is modelled, no shi* sherlock This show how FI is T96 as that is where the shortwave dramas will be resolved. A BOOM chart 5/12 is posted UKMO T168 Signs of lower Euro heights, particularly on the UKMO but both an improvement on yesterday's 12z runs. We are starting to see a closed off High with greater chances of feeding continental cold this way Well on the sinking high, Fergie has said it is the favoured outcome but UKMO does not suggest any quick evolution toward that solution. if this trend continues, such as shown at T144hrs.The high holding just a tad further north makes all the difference. I thought it was going south east wtf If you want to avoid the GFS crud start praying the UKMO is correct! Early evening ECM backs ukmo!!! No sign of South westerlies on JMA.JMA the new must have model UKMO 168 continues the eastward propagation of the Iberian low & sends a tighter squeeze of Easterlies over southern England - Very cold surface air 4/10 Cold (1 more to reflect the 2m temps down south maybe -10c near Benson Oxfordshire tonight , who lives near there ?. I took 0.00002 off for folks living in north Scotland milder there) For those that struggle with what’s going on I attach two simplified charts one showing how hard it is to draw marge and one showing marge struggling with the block re where is it going to go.
  14. 87 points
    WINTER 2016/17 FULL REPORT No. 8 (PART 1) WITH JANUARY 15TH INPUT Please note that some of the charts that I refer to in this post are through “live” links which update periodically. So, if you are reading this a few days or even hours after publication (on Sunday, January 15th at 1900), some of the charts may already have updated. My comments relate to what the charts were showing at the time of this posting. I am just starting to learn how to cut and paste charts into my posts so please bear with me as I increasingly use these in future reports. This is part 1 of my weekly report which will usually appear on a Sunday evening (from now on). It contains all my usual features except Judah Cohen’s latest Arctic Oscillation report. This will appear in part 2 of my report shortly after it is published, which is usually between 2300 and 2330 on each Monday evening. Reacting To The Model Output – A Dose of Reality: There seems to have been just a little activity on here since my last full weekly report (on page 179 of this thread) which was six days ago! We are not far off 100 pages since then and the last 24 hours has been pretty quiet. We had the short Arctic cold snap and many of us saw at least some snow including Londoners (just a few flakes down here in Exmouth). Most of us on here (including me) are obsessed with snow but it seems that some of you were so busy worrying about how quickly it would end and looking for the "easterly" that you did not seem to stop to enjoy it while it lasted! The mood has changed from one of pure excitement and joy to one of utter disappointment and despair. I usually try to manage everyone’s expectations during the former and rally the troops during the latter. The reality is that both types of mood during the last week were overreactions. Not everyone gets caught up in this emotional roller coaster, especially the tiny minority that do not like the cold! With such an intense period of model watching, I fully understand that some of us are suffering from model fatigue and a few days away helps one to recover one’s sanity and perspective on the real world. The "pessimists" will make comments like: the models only verify when they predict a mild pattern; any half decent output will disappear on the next run; the mild ensemble outlier will verify; you cannot trust the GFS (or the ECM or UKMO) or whichever one is the most bullish at the time; this model has been dreadful all Winter; the op or the control run is not representative of the current output; anything beyond D3 is FI; FI is only correct when it is not showing cold; models only ever downgrade when a cold pattern is predicted, they never upgrade; we only really ever get zonal; the PV never gets into a favourable position for the UK; the jet stream always blasts away anything remotely cold; I can only see mild crud or mush; the “euro-slug” never moves away; the HP supporting the northerly will always topple; easterlies are almost impossible to achieve these days; faux cold is not real cold and we may as well have a zonal flow; long range forecasts are always unreliable or wrong; then one liners start to get very critical and usually without any constructive argument presented; moans start to predominate when the output is downgraded; teleconnections science is a waste of time; those making the forecasts or using teleconnections have no idea what they are talking about or are idiots (from the tiny really nasty fringe); this Winter is over; I am leaving the forum, see you next Winter (but they never leave!). Apart from mostly the opposite comments from the pessimists, the optimists can make comments like: look at perturbation 15 on the GFS 18z for T+300 – if that verifies we will be have a raging blizzard across the whole country; when showing a cold pattern – this model has been the most reliable recently; so and so has said that the pattern is almost identical to that of 1946-47; that chart (showing cold) is almost certain to verify; the ens or almost all the members show a cold pattern is probable (when the op shows mild) or vica versa; tweets supporting a cold or snowy pattern are posted, usually with no comments added; well considered comments are misrepresented or taken out of context leading to a huge ramp; I could go on. In reality, depending on the fluctuating model output, many of us could fall into either camp at any particular time. If one avoids being overly optimistic then there should be less despair when things take a turn for the worse. If you can manage the excitement then that’s fine as long as you can manage the disappointment. I am almost always an optimist but not naively so and I try to get the right balance into my posts. The trouble is that the changing emotions often lead to misleading posts and comments. Identical charts can have polar opposite comments. How often do we see a post from a newbie or someone just trying to learn and understand the subject say, “I am completely confused by what people are saying “, when two different conclusions are expressed. There is nothing wrong with well explained comments but throw away one liners can be thoroughly misleading. Let’s drop this snow obsession just for a short while. Many on here enjoy the “chase”, looking for early signs of the next cold spell. This winter’s patterns have been so unusual that almost anything is possible during the next few weeks and there is plenty still to chase. There should be many more opportunities and I’m really confident that something will emerge to really excite the coldies before too long. In fact, even the next week still has some interesting possibilities. I felt the need to make several short posts (by my standards!) during the week to bring some life into the recent sombre mood. A few posts have been drowned out by the critical one-liners. At least this morning, with the thread so quiet, several great posts of encouragement were made. For example, if you haven’t seen them, look back to at least the two from @bobbydog and @stewfox. I thoroughly endorse these views and I will elaborate on them in the next section of this report. Overview Of The Current Model Output and Looking Ahead: In my last weekly report (see page 179) I looked at four broad alternative scenarios that might develop following the conflicting, fluctuating and very uncertain model output beyond around D5 to D7. I still believe that my colder scenario iii is the most probable and that we nearly made it to the coldest scenario iv. Yesterday, I produced a short post (on page 257) where I felt that we would be entering a transition period to a “continental” flow between today and Tuesday and this would be the first critical period for the models. I often prefer to look at all of the six main models (+GFS ensemble means) to see if there is any cross model consensus. I posted up the charts for D3 (now D2) to demonstrate that all the models showed the milder air coming in from the west and coming up against the cold block to our east as well as the receding Arctic cold that had been over us. There is usually a messy transition especially when the Atlantic fails to make proper inroads and the incoming fronts stall right over or just to the east of us. Whatever the fine detail is for today into Monday (a “nowcast” nightmare for forecasters) the position by late Tuesday is “more or less” agreed upon by all the models. The fronts are predicted to stall and be pushed back westwards and fizzle as they do so. We will be left with high pressure building over us and a very gentle east or south-easterly drift. The area of rain (with a little sleet and snow in the east) initially moved from north-west to south-east but has now slowed down and the precipitation is now edging southwards and not eastwards (I am writing this bit at 1500 today). The MetO fax chart below shows the position (just updated): 12z - valid 1800 Sunday 12z - valid 1200 Monday 12z - valid 0000 Tuesday Occasionally, when we see this type of stalling pattern, the push of milder air completely loses its impetus and gets steadily squeezed out at the surface and the colder air takes over much more quickly. I make this point, as this is something that might be very interesting to follow later this evening and into tomorrow. UPDATE: Here are the current surface temperatures posted at 0848 GMT (0948 French/Meteociel time) on Monday, January 16th (note that this updates automatically, so you can follow the changes): This shows the cold moving back in more quickly. The NetWeather radar has just started to show some wet snow developing just west of Ipswich. The cold over eastern France , the Benelux countries and Germany seems to be edging westwards. If this continues, expect the MetO to update their short term forecasts. The more likely scenario will be the one I mention below (written 18 hours ago prior to my update). The models broadly agree on the HP moving over us although there is some disagreement on the extent of the colder air pushing back north-westwards during the early part of this week. Although much of Europe has now lost the extreme cold conditions experienced a few days ago, there is still widespread cold extending over much of the continent as can be seen in the charts below: GFS 12z T+6 current Euopean surface temps GFS 12z T+6 current European 850s Please note: Unfortunately, I am still copying across incorrectly some of my charts. The left one above is frozen but the right one keeps updating. What am I doing wrong - please help! Unfortunately, it was this first transitional period that was recently modelled (up to 2 to 3 days ago) to be the gradual move towards a proper easterly flow developing across the whole country (or at least the southern half). Some of the severe cold (of a week ago) over Europe looked like it might be advected into the UK with cold to very cold surface conditions and very low uppers too. The cold has been substantially modified and the uppers have mixed out to some extent but we may well see some sharp night-time frosts in the south-east (initially). With the dry continental influence and low dew points there may be some decent diurnal ranges with maximum temperatures in any sunshine briefly getting close to average before dropping quickly after sunset. The air may well stagnate with much lower daytime maxima later in the week. Whilst a full on easterly now seems a low probability (at least at this stage), the position of the high pressure may be critical around next weekend. I feel this is the next important phase if there is to be a transition to generally colder conditions in week two. The models really start to diversify beyond D7. Even in a normal winter, the output for this longer term period is usually far less reliable and inconsistent as the models start to explore various options. In this winter with the often weak and conflicting signals we have witnessed some amazing swings even in the D5 to D7 period. Anything beyond that has been very difficult to predict with any real confidence. So, I shall speak in more general terms. There is a useful little chart that gets posted up quite regularly on the MOD by the likes of @karlos1983. This is the ensembles for the surface temperature. I show the 0z chart for London below. London 2m Temperature Ensembles 0z 15th to 29th January This shows the brief milder interlude for today with temperatures already falling back below 5c during tomorrow and closer to 0c in the following few days. After D4/5 the ECM mean shows slightly less cold conditions while the NCEP falls further and the mean remains in the 0c to 5c band. This pattern continues until towards D10 when the NCEP mean suggests another milder interlude. There are a wide spread of ensemble members from D3 onwards and particularly in the less reliable period from D10 to D17. The model output during week two is very uncertain and we may see further substantial swings during the next few runs. I do not feel that a “prolonged” (over a week or longer) period of zonal (with full on Atlantic) is likely. Several models hint at a brief spell of westerlies or south-westerlies but this is well into week 2 and FI (update: while writing this, I see that this is partly indicated on the GFS 12z and slightly more progressively in the GEM 12z output). There is also a hint of the high pressure remaining closer to us. Much would depend upon its precise position with anything from the dreaded euro-slug, to right over us or ridging northwards which might allow another Arctic outbreak and even an easterly! I believe that we are still in a period of transition (for how long I hear you ask impatiently!). Following the evolution during the latter part of January should make for yet more fascinating and, perhaps, very exciting model watching but do expect some more wild swings. I have not yet even mentioned the now quite strongly anticipated Sudden Stratospheric Warming (SSW) event. Although this can take many weeks to propagate down properly to the surface (like last winter), it can also be much more instantaneous. Several posters (who are much better qualified than me to comment on this area of the subject) suggest less than two weeks this time from the start of the warming event. If this does materialise, it will have an impact. This usually (but not always) leads to much of the cold air in the Arctic being released towards the mid-latitudes with HLB and much more meridional patterns being established. It does depend just where the HLB sets itself up but, more often than not, western Europe and the UK do see a decent cold spell developing. A SSW can also interrupt the patterns in a way that might be less favourable for us in this part of the world (like moving the PV to a bad location). So fingers crossed for a strong SSW with fast propagation and positive (cold) impacts heading directly to us! Even without a SSW event we can still have further colder snaps or cold spells later in the winter. The highly unusual winter continues. I do not believe that we could go through two (or even three) months with a very blocked Atlantic and very few cold incursions. I want to believe that the recent Arctic snap was simply a precursor to a more prolonged cold spell. January could well be heading to be a below average month. Just how cold and how snowy it might get is still very much up for grabs, as is February. Arctic Sea Ice News and Analysis: The last full monthly report was published on January 5th. This is a fascinating read and includes a review of the whole of 2016. Please note that the current ice extent map and the comparison chart to the mean are updated daily and are always of interest. Here’s the link for the latest updates: http://nsidc.org/arcticseaicenews/ This chart shows the current extent of the sea ice (as on January 14th) in relation to 30 year means. The “rate of recovery” during December was very close to a record but, despite this, the overall ice extent is still at record lows and remains just below the previous low set during Winter 2012-13. Overall ice growth stalled during the last few days but is to the resume this week (at least in the Baring and Kara Seas which should see some rapid growth due to some severe cold setting, as is demonstrated later in my Svalbaard temperature review). Arctic Oscillation (AO) 14 Day Ensemble Charts (updated January 15th): The Arctic Oscillation is trending positive in the next 2 days and then back neutral with a split after D5 with some members trending negative, some neutral and others going positive again during week 2. This is particularly mixed and reflects the very uncertain model output. Note for newbies: The AO index reflects the amount of HLB in the Arctic. A positive +AO reflects very little HLB and a strongly +AO reflects no HLB anywhere in the Arctic. A negative –AO reflects some HLB and a strongly –AO reflects substantial HLB with more intense high pressure and/or more extensive HLB in various parts of the Arctic. This index produced by NOAA is based upon GFS model output and will fluctuate in line with that. Although ECM produce similar data based upon their own output this is not one of their “free-to-view” charts for public consumption. Here's the link: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml ...and here’s the current chart: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif North Atlantic Oscillation (NAO) 14 Day Ensemble Charts (updated January 15th): The NAO is currently trending from slightly positive to slightly negative later this week before returning to around neutral (with some members still slightly negative and some slightly positive) during week 2. Again a mixed picture reflective of the rather uncertain GFS modelling. Note for newbies: A neutral NAO index reflects the close to average state of the mean sea level pressure patterns or the “climatological” norm in the North Atlantic. This would equate to the anomalous high pressure in the south, particularly around the Azores and low pressure stretching from off the eastern USA seaboard in a wide band running north-eastwards to the east of Newfoundland, east of Greenland and through Iceland. A positive +NAO occurs when these patterns are stronger than usual (eg: the Azores high is more intense or more widespread and/or the Iceland low is deeper or more widespread than usual). A negative –NAO reflects a weak Azores high and/or less intense Icelandic low pressure. A strongly –NAO would reflect a reversal of the normal patterns with relatively low pressure in the Azores and high pressure further north towards Iceland. A “west based –NAO” (talked about recently) is when the pressure is higher than usual in the western Atlantic such as around the Newfoundland area). An “east based –NAO would indicate higher pressure than usual in our part of the Atlantic. This index produced by NOAA is based upon GFS model output and will fluctuate in line with that. Although ECM produce similar data based upon their own output this is not one of their “free-to-view” charts for public consumption http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gif ...and here’s the current chart: MJO Ensemble charts: Here are today's MJO ensemble charts for the big 4 (all updated on January 15th) with the live links below should you wish to check any future changes. UKMO (7 day forecast): ECM (14 day forecast): NCEP/GEFS (14 day forecast): JMA (9 day forecast): COMMENT: A rather mixed picture yet again but slightly more encouraging signs with all 4 models bringing the MJO to life again. The UKMO with it’s shorter forecasting period moves the MJO out of the COD (the "Circle of Death" - the relatively inactive area in the centre of the chart) today and into phase 1 at steadily increasing amplitude and even reaches phase 2. The ECM goes for the same route but then goes back through the COD and is set to break out again this time into phase 6 with a fairly wide spread of ensemble members but in broad agreement. The GEFS is a little different, emerging from the COD in phase 8 at low amplitude and on into phase 1 at good amplitude and then does an about turn back into the COD (remaining just inside the phase 8 and 1 borders) with the ensemble members mostly following a similar trend. The JMA is similar but then keeps the MJO signal in phase 1 at mostly good amplitude. Please Note: Depending upon how much emphasis each model builds in the MJO signals (which I believe is one of the automatic parameters) and to what extent this conflicts with other signals, should be reflected in that particular model’s output. The phases 7, 8 and 1 at good amplification (as at last shown now) is supposed to assist with greater HLB. I have read a few conflicting reports on this with this winter’s unusual patterns and weak signals highlighting some of the possible problems. Some who support the merits of using the MJO as an important forecasting tool have suggested that the signal has been “masked” by other more dominant factors. It does seem odd that the MJO remained inactive during the brief period of HLB and last week’s Arctic outbreak while as soon as the HLB subsides we see the MJO come to life! I see that another argument is that the MJO signal is not as useful as first thought particularly in the winter months when there are so many other strong forces at play. This is beyond my limited understanding but I have been following the debate this month between several of the more seasoned regular posters on the MOD. In particular (in no specific order) I have enjoyed the active discussion between @Nick F, @nick sussex and @Singularity. I highlight your names as I also noted that you have debated the use of Kyle MacRitchie’s specialist MJO predictions and I have some input that you guys might find very useful and I would imagine might stimulate your discussions somewhat further! Last winter I included Kyle’s charts in these reports and used to show these with a cautionary note below wondering why his charts were usually quite different in what the others showed. I had read on Kyle’s old website that his main research "was" on studying the tropical/equatorial forcing mechanisms and particularly the ENSO. His MJO charts (based on raw data drawn from CFS) was an attempt to modify this with the other signals. Following a direct message exchange with Kyle over the summer I decided to suspend showing his charts. I added a brief standard note about this under this section in all my reports for this winter. I feel that I should state Kyle’s full reply now: …”I am happy for you to use my charts in your reports but you must be aware that a full comparison could be misleading. Some of my work is still experimental, particularly where I apply the “modifiers” (for sake of a better description). I have also been rather lazy with the frequency of my updates!....” I was just getting the impression that he wanted to move on into other areas of the subject. Then, just a few days later around last April (hence the "was" above) Kyle closed his old website and opened a new one. This is called "Weather For Vines". I read what he was doing (on his site) and contacted him again. Whilst he will continue his research into tropical forcings and still have some new and regular input on his new site, he now has a new focus. He was always interested in growing vines and the climate parameters required for this. He is now researching the optimum conditions and how things will change through global warming impacts. I think that he also feels that he can make this into a more commercial/profitable business by providing special seasonal as well as shorter-term forecasts for vine growers as well as helping those considering going into that industry. So, I can only imagine him studying the MJO while having a glass or two of some high quality vintage wine! @nick sussex - thank you for your interesting response (in your post below this one) particularly with what you say regarding the assisting of a SSW with the MJO progressing through phases 6,7 and 8 rather than emerging from the COD directly into phase 8 or 1. This may be something to look out for and might the ECM just be factoring in this possibility? Their MJO chart is different to the others from D10 to D14 showing the dive back into the COD and quickly re-emerging towards phase 6 (with most of their ensemble member spread heading in that direction). This might be a pure coincidence and it is well into FI. If they stick with this signal, their D10 model should start to get interesting by mid-week. Just a glimmer of hope but one to monitor. With this in mind, I shall re-introduce Kyle's charts for the next few weeks - here's his current one: and the link: https://weatherandvines.com/?page_id=140 + his explanatory notes and further guidance: https://weatherandvines.com/?page_id=128 It is closer to progressing towards phase 6 and the red ensemble member gets there but not until mid-February. As his charts are slow to update and the SSW signal has only become clearer in the last few days, perhaps his next full update might show a faster progression. Again, just a "possible" scenario but with plenty of interest. Over to you (and others in the know) to use your other sources to see if their is any more supporting evidence. Just to start this "chase within a chase" here are the ECM 0z D10 charts which are probably still a few days too early. They are quite different to the GFS and GEM 0z charts which show a zonal flow. I wonder if any of the ECM ensemble members will provide any hints. I have broken one of my golden rules by going into FI territory but let's have a little fun for a few days! ECM 0z January 16th T+240 - Pressure: ECM 0z January 16th T+240 - 850s: Northern Hemisphere Snow Cover: I show animations for snow cover and sea ice changes. These are produced by the National Ocean and Atmospheric Administration (NOAA). When you go to their site you can change the date range and go back over 10 years. You can change the speed and pause on any particular day. These are brilliant, very informative charts and great to play around with. I’ve have re-set the links below to show the last 2 weeks from January 1st to January 14th but you can change these again on the site: a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA January 14th): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20170101-20170114 ....and here is their current chart: b) Animated Europe and Asia Day Snow Cover (updated by NOAA January 14th): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20170101-20170114 ....and here is their current chart: BRIEF COMMENT: Just look at the rapid build-up of European snow cover during this period (which peaked a couple of days ago). There continues to be well above average snow cover over northern Asia and this has continued to expand southwards and south-westwards. Scandinavia is once again fully snow covered, including the south (the high central plateaus usually have pretty complete snow cover for most of an average winter). Meanwhile, the extensive snow cover over North America has declined sharply due to the much milder conditions there. Current Arctic Regional Surface Temperatures: GFS – Northern Hemisphere Current Temperatures for January 15d 1900 (12z – 1300 T+6): and here’s the link to live charts if you wish to view future changes (updated 4 times a day): http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=6&mode=1&carte=1 Here is my selection of Arctic Regional Temperatures: The the previous readings from my last full report are shown in brackets alongside North Pole: -16c to -24c (-24c to -28c). Barents Sea/High Arctic: -4c to -20c (-4c to -24c). Scandinavia: south -4c to -8c (no change); north -8c to -12c (-12c to -16c). Northern Siberia: -28c to -40c and below (-32c to -40c and below). North West Russia: -28c to -40c (-20c to -32c) North-east Europe: -8c to -12c (-8c to -20c). Greenland: -16c to -40c (-20c to -40c) Canadian Arctic: mostly -12c to -36c (mostly -12c to -40c). Alaska: -12c to -28c (-8c to -20c). Please note: For land masses I have tried to focus on readings away from the coasts and away from any mountainous areas. You can follow the trends by looking at the latest data at any time from now on. It is vital to note the time of day to take account of daytime/night time variations. So for like for like comparisons, for example the 1900 charts for each day should be available to view from the 12z (T+6) updates which are published around 1600 to 1700 or about 4 to 5 hours later. Svalbard Daily “Maximum” Temperature Forecast for 10 Days: Here are the links to the 3 Svalbard stations that I am monitoring together with a summary of D1, D5 and D9 values: Central/West Svalbard – Longyearbyen 28 m asl: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf January 16th -1c; January 20th -12c; January 24th -13c. North-West Svalbard – Ny-Alesund: http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf January 16th +2c; January 20th -14c; January 24th -19c. Central South Svalbard – Sveagruva: http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf January 16th -3c; January 20th -17c; January 24th -22c. Please note that the links above will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at quite short range. BRIEF COMMENT: After the temperatures rise to near or just above freezing tomorrow with some snowfall, they fall back dramatically after that and end up around their lowest levels seen this winter (matching the 2 to 3 days in early December) and down to or even below their 30 year means which has rarely be seen in the last 3 winters! This injection of severe cold should help the Arctic sea ice extent to quickly resume its growth in the Baring and Kara Seas where it is still at record lows right now for mid-January. To put the above figures into context, here is a link to the main Longyearbyen site: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html This shows monthly means and actual highest/lowest temperatures recorded during this winter and goes back further. Svalbard has been seeing “maximum” temperatures often running at 8c to 10c above their long term average throughout most of 2016. This has been the pattern for several years and is reflective of the warming Arctic and record low sea ice cover. Final Comment: An interesting period of model watching ahead with all sorts of possibilities. Next Update: Part 2 of this report with Judah Cohen’s latest update should posted around 2330 tomorrow (Monday) evening. My next full weekly report should be on Sunday evening, January 22nd. @Buzz Thank you for your kind comments (even though the moderators removed it for being off-topic!) - it makes it all worthwhile!
  15. 86 points
    ...precisely so, and precisely echoing UKMO thoughts after some recent flip-flopping of output (including yesterday's ECMWF Monthly, which suddenly offered substantial weakening of the previously strong +ve MSLP anomaly north/NW of the UK that it yielded in the run only 3 days prior and in all previous recent runs, for later December. Is it wholly trustworthy, given marked swing? No, not until we see the sense of direction offered in runs on Mon-Thurs next week. The situation currently is that whilst ECMWF now offers just a bland, weak +ve MSLP anomaly to the west of the UK, it equally - and quite starkly - offers no signal either to suggest a markedly zonal, +ve NAO set-up either.... In other words, whilst GloSea still remains more inclined to return a blocked story later through the month (and ever since output run way back in Sept, has not budged from indicating a massive ramp-up in stratospheric zonal winds later Dec, as now being suggested by GEFS), the forecast outlook by the UKMO remains quite reasonable in the current circumstances (not least as it would be easy to overreact to latest ECMWF in isolation). Thus, a return to blocking still remains the more favoured outcome, BUT whereas this always had low confidence (based purely on lead time), we now can add a further tier of uncertainty given ECMWF yesterday and the fact that no clear synoptic regime is obviously favoured after mid-month. Some reactions I've seen on social media have been bordering on hysteria, but there's nothing that suggests 'Dec 2015 Revisited' has suddenly manifested in model output. So it looks set to get milder through next week.... but does that really automatically, unquestionably characterise a whole winter ahead??? Deary-me ;-)
  16. 83 points
    Given that today's EC Seasonal update remains steadfast on broadscale lack of zonality J-F-M, retaining it's eagerness for marked northern +ve GPH/MSLP and drier than avg anomalies, I'm not expecting any sudden change of tact from UKMO Seasonal Team based on current op modelling mash-up. What is now very striking is the growing evidence of apparent disconnect between impending and strongly-signalled upshift in stratospheric zonal winds, versus zero evidence in EC Seasonal for it to manifest in a marked change of mean tropospheric anomalies (towards zonality). I'm trying to discover via UKMO Seasonal boffins exactly *what* forcing mechanism could be overridingly at play here, because (despite the snipers/doubters on here) it is quite irrefutable that *something* is driving these two key high-end coupled models (EC & GLOSEA) to reach similar prognoses. Fascinating enigma; fascinating times...
  17. 83 points
    Two examples of two people who appear each winter as boorish armchair critics who concentrate on taking apart people who make an effort to offer an opinion (based on whatever research), but offer nothing/nada themselves. This type of repetitious stuff is far more negative and lacking in constructive purpose than anything disappointing that doesn't satiate weather preferences as offered by the computer models Have a nice evening, whatever the ECM extended offers
  18. 82 points
    Precisely T. The obsession with shortwaves is delusional IMO, as is the reliance and buying into ops for anything beyond day 5 in this current set up. The modelling is getting to grips with the speed of the upper trough moving across North America in the medium range. The fact that this delivers more of a mid Atlantic ridge is no surprise here. I like the GFS op which echoes nicely the ensemble guidance we're getting, and which reflects the longer term thinking on the GWO. It delivers a cold pattern, which will remain cold for some time after, it obliterates the Euro ridge. It also exercises the sub-tropical jet over Mexico. It is here that those critical fluxes in momentum will manifest themselves subsequently in terms of the North Atlantic profile. The fact that the GFS is playing around with this idea (and the ridge close to Greenland) in the extended range should be noted. GEM Ensemble and EC EPS means look very good over the Arctic in the extended. Timing wise, I'm actually advancing my thinking on NAO flip to around the 23rd-26th January period.
  19. 81 points
    Afternoon All- So before we run out on the 12s I thought I would run through the evolution / possibilities - * I think its safe to say that in the history of model watching other than 2010 for snow that has got to have been the best GFS run ever - encapsulated by these x2 charts- -20 T2M anomalies is net the same as having a maxima of 0c in august ( in comparison ) thats how cold it is V the norm. So what was mentioned earlier is 2 distinct phases we seen from the 06z, one the longwave pattern - IE the main blocking High pressures & the more detailed shortwave pattern that is the movement of low pressures / shortwaves & crucially the triggers for pulses of WAA & CAA- Yesterday when round 2 of cold seemed 50/50 ( mainly from the GFS ) my talkinh point was the potential phasing of the 2 low pressures over the NE of US- here was the 12z 132 chart & the 18z 126 under the microscope The first chart shows the energy digging south & not allowing the high pressure from the atlantic to ridge NW - the 18z was an improvement because it clearly showed the potential for ridging to evolve... we now see the 06resolution for the same timeframe- ( but 12/18 hours closer in terms of resolution ) we see the energy is no longer digging south because that ridge from the NE states ( otherwise known as -PNA ridge ) has just poked its nose eastwards- This was 100% crucial this happened because when the jet does start to amplify some 24-48 hours later it moved the placement of the low eastwards & it starts cutting SE over iceland instead of SW greenland - the net result of all this is this 'trigger' low is going down the east of our UK high pressure instead of the west - seen here - So 144 tonight is the 'point' of no return tonight in terms of phase 2 of cold & it hitting the uk at @168 - specifics TBC however the 168 mean suggests a flow somewhere close to NW swinging to Northerly at 192- * The reason I have slide the shots over to the left on the NH is to show the clear example of the atlantic pressure forcing a split in jet energy over SE greenland- note the x2 low pressures one going SSE into the atlantic & one going NNE up to the pole. At 192 The second crucial phase of the longwave pattern sets us up for 'sustainability' of the cold spell & is the 'tricky' bit of the hurdles we have to get over- Its all about how much forcing & split is applied on the jet by the high pressure ( wave ) developing over southern greenland - 1 Direct way to measure our potential success 2/3 down the line would be focussing on those 2 lows & their vectors @192 - * The north west Greenland one ideally needs to be going NNE between a range of say 10 degrees & 20/25 degrees * The one in the atlantic needs to be going SSE - between 135-165 degrees - note the 06z angles More or less perfect @ 216 - with ECM below, equally as awsome So x2 clear phases of development from 144-216 * how much ridging we get through the middle & how much of a wave northwards does it create - - The jet profile from 00z to 06z at 192 suggests the same pattern just a biggger wave amplitude on the 06z- ( 06 first ) So with reference to @frosty ground who I said to earlier - should we get to 192 with this type of jet with an amplitude to 80N which screams back south then the cold @ 216-240-264 is all but guarenteed from the east- Thats because you are a lobe of sub -20c air sitting on its northern flank- you have the jet pulling it south & the low wedging the cold air west- * post that the jet alligns perfect to have low pressure arriving from the NE into the deep cold meaning nothing but snow for the UK-- so the landmarks are 120-144 high pressure wedged into NW atlantic as much as possible 168-192 high amplitude wave - as much as possible over western greenland to create the loop 192 >>>> jet dives south to take the trigger low with it- chances -- 60-70% to get the loop & cold from the North & 25% is to get the surge westwards from the east as recent years havent seen a high enough amplitude & all the cold goes west through Northern France... ciao S
  20. 80 points
    EC MONTHLY: again like last run. Blocked & dry anomalies developing 1st half Jan as heights move W to north of UK. Colder than avg anomalies southern UK 2nd week Jan (not seen that signal for a while!). East-NE flow. So continuity between last runs and ditto with GloSea5. Don't shoot messenger. Just describing the output: not making any comment on outcome.
  21. 79 points
    Please note: I have copied this post across to the "in depth thread" should anyone wish to discuss any points that I have raised and share their views in a less frantic environment WINTER 2016/17 FULL REPORT No. 12 WITH FEBRUARY 5th INPUT This is by far my most upbeat report of the whole winter (whatever any of the 12z model output might say!) Brief Review Of The Last Week: The widely predicted change from the cold continental influence to the more unsettled Atlantic influence was completed early in the week but not without further cold days in the north and north-east at first. The named storms, indicated on much of the model output a week ago, did not reach us but took a more southerly track into France where they named one storm “Leiv” but fortunately the severest damage was restricted to a very small coastal region in western France. The following storms were less intense. We were on the northern edge with some rain and briefly some stronger winds in the south and south-west. Although temperatures have recovered to some extent they have (mostly) only slightly exceeded normal on a few days and were generally in single figures with even a little wintry precipitation on higher ground in some parts. The Current and Short Term Position: I felt that this milder spell would be brief and kept a careful watch on the European cold block which I have said time and again during the last month has been consistently under estimated by almost all the models. I believe that this is still being under estimated and this time it will greatly assist us in the feed of deeper cold air into the UK by next weekend. In fact, I felt so strongly about this that I started a “Daily European Temperature and Pressure Watch” three days ago. My latest update was posted this morning (see page 92). The cold block was only pushed slightly eastwards into western Asia. Much of central and eastern Europe only briefly saw temperatures rise slightly above freezing (for a couple of days). The UK Atlantic spell is being cut short. Fronts will be stalling across the country during the next three days as a Scandinavian HP takes hold. There may even be a little snow as the fronts return westwards before they fizzle out. Right now, pressure is building strongly from north-west Russia and is already ridging into Scandinavia – just look at my live pressure chart on page 92 and compare that to the 0650 chart. The deep cold is also steadily intensifying in north-west Russia and moving south-westwards into northern Scandinavia. The sub -20c pool of surface cold (some is nearer -30c) and sub -20c 850s are also expanding and moving steadily westwards and south-westwards. I believe that the transition may well be even faster than currently predicted with colder weather installed by mid-week. I also think that there is a good chance that the small area LP that moved across south-west England today will move away into France. Then the fronts associated with the following larger area of LP tomorrow may not make much progress into the UK and there might be a good chance of a new small LP forming on the warm front or near the occlusion which could move away south-eastwards and further undercut the block, introducing easterlies further south into the UK a day or so sooner. I demonstrated the predicted development of the Scandinavian HP in another post yesterday (see page 84) where I used all the Met Office fax charts. I had noted that their latest charts (which were issued several hours ahead of the 12z model output – they always give an advance clue to any likely near term changes) were showing the HP being maintained further north and west over Scandinavia and with a better alignment for the easterly on its southern flank. Some of the models are still struggling with the all important detail on this. I indicated this morning that there were already several undercutting LPs propping up the HP. Okay, I had better post the two live charts now to make my points clearer (but just take another look at all the charts on page 92 to fully appreciate the extent of today’s changes): EUROPEAN "LIVE" PRESSURE CHART EUROPEAN "LIVE" TEMPERATURE CHART At this stage, my take on this is that the Scandinavia HP will not sink southwards, at least for quite a few days. I also believe that with this and the under estimated depth and extent of the cold pools (upper and surface cold) that conditions will turn somewhat colder across the whole of the UK sooner than much of the recent model output has suggested. I do note that the 0z output has mostly upgraded the colder uppers. I am writing this part of my report at 1330 and by the time I post it this evening, the 12z output will have rolled out. I am expecting further upgrades over the next few runs but perhaps still with the odd single run/single model set back. The models mostly still need to factor in the current extent of the cold and as they update they should reflect these changes in the D3 to D6 range. Now, I am not trying to score points over anyone (and it would foolish to try to take on the models for any extended period) and I may be wrong about this but let’s look at some more evidence. I noted an interesting point that @johnholmes raised several days ago which I completely agree with. The strength and persistence of HP and/or cold blocks is frequently under estimated by the models. In fact I would say that this is often one of their most serious faults or shortcomings and presents huge timing issues and even leads to quite a different outcome on occasions. In the days when forecasters did not have access to computer models, satellite imagery and all the other modern tools, they often had difficulties in assessing the longevity of these blocks. Much of their forecast was based on pure experience and using analogue charts alongside the current data. As John says, it is amazing that these blocks still present such forecasting difficulties. Many on here have said, easterly airstreams have been much rarer in recent years. Back in the 1960s to 1980s they were so much more common. Not just in cold winters but we usually saw several of them even in predominantly mild winters. I can recall a great many examples of all sorts of types of easterlies but this is not the time or the appropriate thread to list them now. In broad terms, the most important component was “usually” the Scandinavian HP. Its position, orientation and how it developed was always so important. Some develop as a temporary extension of a Siberian HP. Some develop in situ, often after an Arctic incursion, when the LP fills up quickly and HP forms over the residual surface cold. Some are transient features and some stick around for days or even weeks on end. Some form when there is no cold pool to tap into. I recall a few easterlies with temps hardly below average. Some produce long periods of cold to very cold but completely dry weather. Some produce a few snow showers on exposed coasts but nothing more than a few flurries inland. A few produce much more convective conditions with rather heavier snow showers often merging into longer periods of snow. Isolated cold pools (those that have broken away from the main cold lobe, like the one indicated on one of the GEM runs two days ago (that disappeared on their next run), small disturbances and troughs can produce snowfall, sometimes developing quite unexpectedly. Streamers can form in the more favoured downwind well aligned spots (like the “Thames Streamer” on a direct easterly flow) and produce many hours of almost continuous snow showers with significant accumulations. There can sometime be more general snow events when Atlantic LPs and their attendant fronts come up against the cold block. Down here in the West Country there have been a number of severe blizzards when stalling fronts undercut the easterly or south-easterly flow. These are rare events but can turn up in mostly mild winters (such as February 1978) as well as in severe winters (with multiple events in 1947 and 1962-63). Sometimes an easterly is swept away rapidly by the Atlantic (probably with the Jet Stream powering up with a more direct attack). Sometimes a LP over Biscay or France veers the flow to the south and pulls in much milder air. So what sort of easterly will this one be and will it deliver any snow? Unfortunately, the answer is that I do not know for sure but there are some very positive signs. Factoring in some of what I’ve just mentioned, I am very encouraged in the way that this Scandinavian HP is developing. This is from the north or north-east into Scandinavia. There is already a good supply of surface cold. This is now being topped up with even deeper cold as I have already shown. HPs often sit over some of the coldest surfaces available. I feel that there is an excellent chance that once the HP sets up over northern Scandinavia, that it will maintain a similar position for quite a few days. The next thing is the LP areas on the southern flank. The very latest position on the live pressure chart shows another really encouraging sign – the central European LP is already helping to re-orientate the HP. I think that within 24 hours it will be far more on an east/west or east-north-east/west-south-west axis. This means a more direct easterly. The strength of this flow will be determined by the intensity of the HP and how close are the LP(s) on its southern flank. The increasingly cold air should then filter south-westwards in this flow. The south of the UK in particular may well be far enough away from the HP to the north-east to encourage some convective activity. If we can get sub -10c uppers in, then things could start to get much more interesting. For now, I would say just some snow showers on exposed east coasts but all to play for in the finer developments during the next few days. Next Weekend and Into Week 2: So how long will this last for and just what can go wrong. I know that some on here like to be more cautious and it can be wise to manage expectations to avoid future disappointments. Others can get taken in by all the ramping with the very bests charts greatly outnumbering the less goods ones being posted (I wonder why!). After all the disappointments we have seen so far this winter as well as in several recent winters it would hardly be surprising to see quite a few members taking a sceptical view. I believe that this will be a rare occasion when things might just go right for us coldies. This has been a highly unusual winter with persistent blocking restricting any Atlantic influence to the minimum. Blocked winters usually have prolonged cold spells. The vast majority of the blocking this winter has been MLB. This has allowed for some exceptional cold over Europe but we have mostly been just on the outer edge of it. There has been a highly anomalous area of HP very close to the UK for much of the last three months. Several posters have said if only we could have the HP a little further north. Well your wishes are about to be granted! I believe that there is now an excellent chance of HP being located to our north-east and later to our north or north-west for much of the next six weeks. Let’s have a look at the Jet Stream. The main arm has taken a more southerly track recently and the northern arm has broken up with a returning flow circling Scandinavia (which may help to maintain the HP or conversely, the HP is partly deflecting the flow of the Jet. Northern Hemisphere Jet Stream – Current Position: GFS 12z T+6 Moving on to D6, let’s have a look at several cross model Jet Stream charts. The main arm continues to be deflected to our south. The southern arm drives through the Mediterranean and south of most of Europe. This should carry LPs systems along that path and this will also help to underpin the HP further north. Northern Hemisphere Jet Stream for Sat 11th Feb – 0100 (with adjusted times to provide an accurate comparison): GFS 6z T+144 NAVGEM 6z +144 GEFS ens mean 6z T+144 Another useful indicator for assessing the likely future strength of the Jet Stream in the Atlantic is the thermal contrast between the eastern USA and the adjacent ocean. Right now and for at least the next week much of the USA will continue to have an unusually mild period. Canada is pretty cold but it rapidly turns milder further south. So, nothing here at all in helping to power up the Jet Stream. Northern Hemisphere Current 2m Surface Temperatures Northern Hemisphere Current 850s GEFS ens mean 12z T+0 GEFS ens mean 12z T+0 Northern Hemisphere 2m Surface Temperatures for 1300 Sat Feb 11th Northern Hemisphere 850s for Sat Feb 11th – 1300: GFS 12z T+144 GEFS ens mean 12z T+144 I have seen several poster’s concern over the chance of an Iberian LP drifting northwards over France and pulling in milder air with it. If the southern arm of the Jet continues to blow strongly through the Mediterranean there would seem to be a slim chance of this. In my experience, it is the slacker flows that can be prone to this. Even here, there are some examples of the milder air not being able to penetrate the surface cold and the warmer air is lifted over the cold which can produce far heavier snowfall or occasionally freezing rain. I call these events “cold southerlies”. They occurred repeatedly in the two epic winters of 1946/7 and 1962/3. In fact most often in the two Februarys. I’m not saying that the 2017 cold spell will be anything like those two winters but entrenched deep cold will take an awful lot to shift it – not a gentle push from the south. A Brief Look Further Ahead: I have not yet even mentioned the stratospheric changes and the multiple warmings in the Arctic. As I said in my report last Sunday (and repeated in several of my updates during the week) there was a good chance that even if the first warming fails to produce a true easterly that there would be one or two further opportunities. I was very reassured to see the latest updates from several of our strat experts like @chionomaniac that the PV should be split for a much longer period. In fact it may well be shattered! The MJO (see later) is predicted to enter its key phases through 6, 7,8 and 1 in the 10 to 15 day period. @Tamara, in her update today, maintained her view that the key background signals should all assist with much greater HLB. The result of this could be twofold, both are cold outcomes - either maintain and strengthen the existing Scandi block or encourage height rises towards Greenland with a broad Arctic flow established. In our longest cold spells we have sometimes seen several switches between easterlies and northerlies and back again. There could be a brief milder interlude during any transition and all the models have been struggling with this in terms of timing, extent and how long will it all last. I am going to stick my neck out and say that it will remain cold for the rest of the month (possibly well into the first half of March too) and it will be very cold for quite long periods. How much snow we might get is very difficult to for anyone to predict but the longer the cold spell continues the greater the chances. I am still very optimistic for the initial easterly to produce at least some of the white stuff. Can it all go wrong – yes it can but I feel that this is our best chance in four years for a memorable cold spell and there is so much positive evidence in favour of it. Now on to my routine coverage. Arctic Sea Ice News and Analysis: The last full monthly report was published on January 5th (next one due very soon). This is a fascinating read and includes a review of the whole of 2016. Please note that the current ice extent map and the comparison chart to the mean are updated daily and are always of interest. Here’s the link for the latest updates: http://nsidc.org/arcticseaicenews/ This chart shows the current extent of the sea ice (as on February 4th) in relation to the 30 year means. Source: National Snow and Ice Data Center (NSIDC) The “rate of recovery” during December was very close to a record and there has been a continued recovery (with several pauses) during January but, despite this, the overall ice extent is still at record lows and remains just below the previous low set during Winter 2012-13. Arctic Oscillation (AO) 14 Day Ensemble Chart: Here's the link to the daily charts: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml ...and here’s the current chart which updates automatically each afternoon: Note for newbies: The AO index reflects the amount of HLB in the Arctic. A positive +AO reflects very little HLB and a strongly +AO reflects no HLB anywhere in the Arctic. A negative –AO reflects some HLB and a strongly –AO reflects substantial HLB with more intense high pressure and/or more extensive HLB in various parts of the Arctic. This index produced by NOAA is based upon GFS model output and will fluctuate in line with that. Although ECM produce similar data based upon their own output this is not one of their “free-to-view” charts for public consumption. COMMENT (relating to the AO chart above when it was showing February 4th data - it updates automatically each afternoon): The Arctic Oscillation is currently negative and many ensemble members go into much stronger negative territory into week 2 (the strongest for the whole winter) but a smaller number of members trend back towards neutral. This reflects the GFS model uncertainty around D8 to D12. A possible switch to HLB and a northerly, a continuation of the Scandi HP or a breakdown with a milder Atlantic influence. North Atlantic Oscillation (NAO) 14 Day Ensemble Chart: Here's the link to the daily charts: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml (click on the small chart there) ...and here’s the current chart which updates automatically each afternoon: Note for newbies: A neutral NAO index reflects the close to average state of the mean sea level pressure patterns or the “climatological” norm in the North Atlantic. This would equate to the anomalous high pressure in the south, particularly around the Azores and low pressure stretching from off the eastern USA seaboard in a wide band running north-eastwards to the east of Newfoundland, east of Greenland and through Iceland. A positive +NAO occurs when these patterns are stronger than usual (eg: the Azores high is more intense or more widespread and/or the Iceland low is deeper or more widespread than usual). A negative –NAO reflects a weak Azores high and/or less intense Icelandic low pressure. A strongly –NAO would reflect a reversal of the normal patterns with relatively low pressure in the Azores and high pressure further north towards Iceland. A “west based –NAO” (talked about recently) is when the pressure is higher than usual in the western Atlantic such as around the Newfoundland area). An “east based –NAO would indicate higher pressure than usual in our part of the Atlantic. This index produced by NOAA is based upon GFS model output and will fluctuate in line with that. Although ECM produce similar data based upon their own output this is not one of their “free-to-view” charts for public consumption. COMMENT (relating to the NAO chart above when it was showing February 4th data - it updates automatically each afternoon): The NAO is currently positive and most of the ensemble members trend gradually towards neutral but remain slightly positive. Although we have the Scandinavian block much of the Atlantic is still dominated by LP. The NAO is not particularly important at this stage. If the block moves further west, we may see a slightly negative east based NAO later on. MJO Ensemble charts: Here are today's MJO ensemble charts for the big 4 (all updated on February 4th) + Kyle MacRitchie’s modified chart (by request following recent discussions) with the live links below should you wish to check any future changes: UKMO (7 day forecast): ECM (14 day forecast): NCEP/GEFS (14 day forecast): JMA (9 day forecast): Kyle MacRitchie (30 day forecast): UKMO: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ukme.shtml ECM: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml GEFS: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml JMA: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/jman.shtml Kyle MacRitchie https://weatherandvines.com/?page_id=140 and his explanatory notes and further guidance: https://weatherandvines.com/?page_id=128 COMMENT (relating to charts showing February 4th data - they update automatically each afternoon): What an amazing set of charts – a full house! The big 4 and Kyle MacRitchie all show the MJO entering the keys phases of 7,8 or 1 at very good amplitude. The best signals, I think for several years. A few of the ensemble members go off the chart in phase 8! This is perfect timing and along with the second (and possibly third) warming events should greatly assist with considerable HLB as we move through week 2. Over to our experts for a deeper analysis. Northern Hemisphere Snow Cover: I show animations for snow cover and sea ice changes. These are produced by the National Ocean and Atmospheric Administration (NOAA). When you go to their site you can change the date range and go back over 10 years. You can change the speed and pause on any particular day. These are brilliant, very informative charts and great to play around with. I’ve have re-set the links below to show the last 2 weeks from January 21st to February 4th but you can change these again on the site: a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA February 4th): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20170121-20170204 ....and here is their current chart: b) Animated Europe and Asia Day Snow Cover (updated by NOAA February 4th): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20170121-20170204 ....and here is their current chart: COMMENT: Part of central and much of eastern and south-eastern European is still snow covered. There continues to be well above average snow cover over northern Asia and this has expanded even further southwards and south-westwards – in fact it is quite exceptional. Scandinavia is fully snow covered, except the south of Sweden (the high central plateaus usually have pretty complete snow cover for most of an average winter). The extensive snow cover over North America has declined during the recent much milder conditions and this is likely to continue during the coming week or so The extensive snow cover over west Asia, Russia, eastern Europe and Scandinavia is another very important piece in the jig-saw as far as our forthcoming cold spell is concerned. This should greatly assist in getting the deeper surface cold in and maintaining very low temperatures for much longer – strengthening the block further. Current Arctic Regional Surface Temperatures: GEFS ens mean– Northern Hemisphere Current Temperatures for February 5th 1900 (12z – 1300 T+6): and here’s the link to live charts if you wish to view future changes (updated 4 times a day): http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=6&mode=1&carte=1 Here is my selection of Arctic Regional Temperatures: The the previous readings from my last full report are shown in brackets alongside North Pole: -20c to -24c (-20c to -28c). Baring Sea/High Arctic: -16c to -24c (-8c to -16c). Scandinavia: south -4c to -8c (mostly -4c); north mostly -8c (mostly -4c). Northern Siberia: -32c to -40c (-24c to -40c). North West Russia: -16c to -20c (-12c to -24c) North-east Europe: 0 to -4c (-8c to -12c). Greenland: -16c to -32c (-20c to -40c) Canadian Arctic: -24c to -32c (-16c to -32c). Alaska: -12c to -20c (-8c to -16c). Please note: For land masses I have tried to focus on readings away from the coasts and away from any mountainous areas. You can follow the trends by looking at the latest data at any time from now on. It is vital to note the time of day to take account of daytime/night time variations. So for like for like comparisons, for example the 1900 charts for each day should be available to view from the 12z (T+6) updates which are published around 1600 to 1700 or about 4 to 5 hours later. Svalbard Daily “Maximum” Temperature Forecast for 10 Days: Here are the links to the 3 Svalbard stations that I am monitoring together with a summary of D1, D5 and D9 values: Central/West Svalbard – Longyearbyen 28 m asl: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf February 6th +3c; February 10th +1 c; February 14th -5c. North-West Svalbard – Ny-Alesund: http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf February 6th +2 c; February 10th +1c; February 14th -5c. Central South Svalbard – Sveagruva: http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf February 6th +2c; February 10th -2c; February 14th -8c. Please note that the links above will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at quite short range. BRIEF COMMENT: Temperatures have risen just above freezing during the last few days with one of the warmest periods of the winter. This followed one of the coldest periods in the previous week (even below the 30 year means). The southerly winds brought quite a bit of snowfall with more to come. It is only after next weekend that temperatures are set to fall again. To put the above figures into context, here is a link to the main Longyearbyen site: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html This shows monthly means and actual highest/lowest temperatures recorded during this winter and goes back further. Svalbard has been seeing “maximum” temperatures often running at 8c to 10c above their long term average throughout most of 2016. This has been the pattern for several years and is reflective of the warming Arctic and record low sea ice cover. Final Comment: As I’ve already said, I am extremely positive about the forthcoming very cold spell. I feel that there is a good chance that this will last for at least 2 to 3 weeks and perhaps well into March. Now will I be eating humble pie next weekend – I do not think so! Next Update: My next full weekly report should be on Sunday evening, February 12th.
  22. 78 points
    I won't say much, might jinx it, but now full set of EC Clusters are out there is a rather large area of high pressure setting up shop over Greenland and across northern polar regions in general towards the end of the run, which is 360hr so the 14th of December. There is a population of 23 members showing this, the other 28 simply show yet another blocking high developing over the UK but with this showing some northern development too. Building blocks... Matt.
  23. 78 points
    If I could interject here.... The upper level divergence signal in the Indian Ocean (MJO related) is slowly edging across the Indian Ocean towards the Tropical Maritimes. That is a region where the GEFS frequently struggles and shows negative bias, so given the importance of this tropical driver, I would not be in a rush to back the GEFS means here - this is not the model to show us out of next weeks rather large trough dominating north and north-west Europe. With the tropical signal migrating through the Indian Ocean, we should see a fall in pressure to the east of the Himalayas and pretty rapid spike in tendency in relative angular momentum and the Global Wind Oscillation move towards phase 4. That's a decent signal for Rossby wave influence for rising pressure over NW Europe within a 10-15 day timeframe. EC EPS 00z going for a pretty impressive turnaround in pressure end next week into the following week, with the longwave trough replaced by a moderate strength +ve height anomaly centred to our east. So much more settled and becoming warmer again in the extended outlook period.
  24. 77 points
    ECMWF Seasonal just released: extensive +ve GPH/MSLP to N/NW/NE of UK through its D-J-F suite. Consistent signal with last run.
  25. 76 points
    Worth adding that latest EC Monthly again raises GPH/MSLP to our NW with mean N'ly flow as we switch into Dec. Interestingly it then also develops (2nd week Dec) quite marked -ve GPH anomaly from Scandinavia to the UK, coupled to equally marked -ve MSLP across S UK and directly eastwards into adjacent NW Europe, with attendant appearance of +ve PPN anomalies by that stage. Fascinating times indeed.
  26. 76 points
    Well I will try my own continued thoughts from recently anyway. Stewart would I'm sure be able to give you a more technical insight answer Trust in the upstream loaded amplification pattern was a main mantra of the last post. The last couple of days have been well worth sitting out I think whilst intra day modelling has ground on with solving the minutia placement details of this upstream pattern shaking hands with an end of the line euro/UK trough buffer. Almost insidiously, ongoing GFS machinations aside, agreement is being reached (and it will be) on the upcoming cold spell lasting into next weekend at least. Meanwhile, out in the bigger picture, with these fundamental changes happening across the synoptic pattern, we should also continue to trust in the insanity of the state of the atmospheric circulation to provide us with more than just a one-off cold spell this winter - following the ridiculously above average temperature pattern in UK and NW Europe of the first half of this winter , Its a historic Nino atmospheric response for sure, and it cannot be emphasised how unusual this is, and hence the modelling dis-array at the same time as a tropospheric tsunami assaults a cold vortex from below and starts changing the northern hemisphere pattern which is becoming increasingly receptive to very high AAM poleward flux plumping up amplified ridges at higher latitudes in stark contrast to what we have seen so far this winter That is of course the same link as posted by Lorenzo this evening with his good analysis on the other page - but for my purposes of reply, the supply line of those deep orange colours above the total AAM line graph (which are indicative of poleward directed Teflon coated Pacific westerly wind anomalies) is far from finished and will continue to have implications for the polar profile and our upstream jet implications in the further outlook period and indeed the rest of the winter Simple me as I am I've not , and have not at any time this winter as most will know, used composites or analogues beyond (in the here and now) keeping Jan/Feb1983 as a mental benchmark comparison (which I'm very pleased Stewart endorses) in terms of the way the atmosphere is behaving - although 2016 eclipses it in response extremes. In truth, I am finding comparative analogues impossible anyway to find based on the uniqueness of the ocean/atmosphere state of 2015/16 A few things though: 1) First of all there is further significant kelvin wave activity in the Pacific generating yet further westerly winds to be fluxed poleward and supplement ongoing amplification from upstream, and bolster atmospheric angular momentum. WWB's are common right through the mature stages of Nino events but based on the unprecedented nature of this one, what is important is that its forcing influence looks set to become increasingly focussed from the Central Pacific as relative cooling continues on both eastern and western perimeters of the ENSO regions. This more centralised forcing teleconnects increasingly, the longer the winter goes on, to subsequent +AAM based poleward flux increasingly shifting the Atlantic pattern east and locking in any future amplified ridges accordingly - so that the cold cannot lift out as easily as a west based pattern - especially with cold air rapidly accumulating to the NE to quickly tap into *See 3 below* As I posted the other day, with Feb archive charts, this type of synoptic representation occurred in Feb 83 - with the amplification ridges eastward of where the upcoming amplified pattern looks to be setting up. We maybe very slightly ahead of 1983 even in terms of latent amplification potential. Its going to be highly interesting to see exactly how the rest of Jan, and especially Feb pan out. 2) In conjunction with 1) to the amplified supply line, It looks to me that we are on an accelerated track in terms of the next tropical convective cycle back to the Pacific that raises large doubts about the current modelling interpretations post next weeks amplified cold pattern to return to a +AO/NAO. Certainly anything sustainable. I wouldn't be too taken in by the COD ( no added interference of any kind with the base Nino state) and or new cycle Indian Ocean influences dampening GLAMM at face value Based on what were very tentative indications of the start of the current cycle (now concluding) which I posted at that time (end of November) as indicative of future activity finally arriving in the Western Pacific by New Year and having implications as one major contributor to a mid season regime change (which we are now seeing), I am taking similar very provisional tentative ECM ensemble hints of a rapid recurve of the next MJO cycle through the COD diffuse response area and back towards Phases 5/6 as indications of how the regime change is set to kick start fast track seasonal tropical activity. Fast enough to highly impact February Any accelerated tropical convective cycle track, in itself, tells you that a business as usual sustained +NAO is counter intuitive, and I think that the models will underestimate the latent amplification flux lagged in the atmospheric circulation, and, as the vortex continues to be assailed by WAA attacks from the Pacific conveyor,and the natural seasonal longwave pattern tightens the screw, the models will overestimate increased polar jet flow (as a result of underestimating +GLAMM or overestimating the effects of any drop in relative AAM) that in turn would suggest sinking ridges back into Europe and instead adjust jet flow back south accordingly Wrt the extratropical GWO signal which will be a much better guide to the way the synoptic patterns unfold than just taking the tropical MJO signal in isolation - an orbit through Phase 7 is ahead, tropical activity waning (temporarily), and then, as further wave flux from the Pacific ramps up AAM yet again, a further obit return to Phase 5/6 which is favourable for any mid latitude ridge still around close the UK to morph NE into sourcing some of that cold from Scandinavia. Beyond then, further retrogression looks good to take advantage of the next round of amplification coming from upstream. Next time, less west based. We then look towards further possible MJO Pacific torpedo engagement as discussed above 3) In addition to this poleward flux bombardment, we have the increasing instability of the trop/strat profile in relation to the Kara Sea height anomalies as a result of the seasonal sea ice anomaly departure albedo feedbacks. The current erratic modelling is illustrating hints at this well enough, and this also supports heights to our NE playing a part increasingly in the extended period In simple terms we have different tin openers in operation eating away at the vortex: The immediate effects are appearing less remarkable in proportion to the assault that is taking place above our heads, but my little analogy here of the way the trop/strat hemispheric pattern is heading through the second half of this winter is like looking at a wide car windscreen which receives a few very potent but finely focussed blows from separate pieces of debris in the air while the car (the vortex analogy substitute) is driving very fast on the motorway. The initial reaction of the glass is to crack and split at the stress centres. But then over a period of time, the stress fissures in the glass start to gather minute fracture faults and extend over wider and wider areas..... So, ignoring the intra noise model shenanigans, the overall song remains exactly the same as before. As previously covered. The cold upcoming period is well in focus, and, a following a pause and further re-arrangement of the deck chairs thereafter we are set up up for another assault into February and, imo, the coldest potential of the winter
  27. 75 points
    So this is a difficult post- Trying to illustrate the GFS trending & How its moving towards the UKMO every 6 hours... We have to go from this ( yesterday ) 12Z 180 To this ( Note the its SAME timeframe ) * the First chart is yesterdays 12Z at 180 - we will run each GFS from there & show how it changes- * to the above chart ( the forecast ) - where the winds across Europe are Easterly all the way into the UK - Key differences. - GFS yesterday has ALL the flow westerly across Europe, No proper ridge ahead of the low in Scandi & least of all NO easterly flow across Europe. So yesterdays 18z 174 Chart continues the stark westerly flow - look where the cut off low is- all the way in SE Europe, there is NO net easterly flow in Europe & NO high pressure over Scandi- So todays 00z 168 Chart- Still emphasis on the westerly flow - - Look where the cut off low is - its edged west, also there is more atlantic amplification - however it doesn't make to much difference- there is still no Easterly flow across Europe. So todays 06z 162 - Changes afoot? - Hang on Where did the ridge suddenly appear from?- The GFS is suddenly making more of the amplification than before & squeezing some heights ahead of the low, Also notice Europe now all of a sudden has some NE flow, meaning instead of the deep cold being swept away its actually being held in situ -perhaps nudging west- So todays 12z 156 - More changes? - Look at that ridge !! Now more pronounced & all of a sudden theres Easterly Flow across Europe pushing West, also the jet is more acute. -- * These 4 runs show the GFS is slowing down its forward momentum in line with the UKMO, becoming slower- From ZERO ridge @ 180 to a pronounced ridge @ 156 all in the space of 24 hours!! - What will the T134 GFS look like tomorrow- This ridge will only become more apparent & more supported if the deepening low off the Eastern US - 132-144 hugs the coast & amplifies the pattern The GFS hasn't resolved this yet as it keeps recurving it off the coast early- However it is moving towards the UKMO tonight- If you look at all 5 images go from 1 to 5 notice2 key things * The high is sharpened up & the pacific low is slower & has a negative tilt in the last frame.... So the key developments are above to the NORTH of the UK & also in the deep south of the states at T96 - where the GFS is faster than UKMO - see here- UKMO coming up sharp, GFS is shallow I hope this helps people trying to understand why the GFS is flat & the UKMO is much much better - GFS has an eastward bias as we all know S
  28. 75 points
    Afternoon All - Firstly appologies for postings yesterday, I think seeing a bit of red on here then getting the same over on TWO stoked up the fire so to speak -- ( @JohnP speechless would be an upgrade lol ) Anyway-- I posted the same on TWO so I will post it on here ( & TEITS et'al some of it is a reply to your comments -) I think many on here perhaps have me wrong- most people on here like to post / read the balanced view- however thats not really for me, we know that for every cold output past 96 there is a balanced view that could counter any potential cold- we have been there so many times its almost pointless raising the concerns as we should just 'know' all I like to do now is add in the probability chance of whats being modelled occuring ( 60/40 etc ) I will always highlight the possible route to cold as thats what most of us want .. but remember the probability that comes with it... just as a one off though- The balanced view yesterday indicated that the jet be weak enough to allow a for mid lattitude ridge to bump the flow over scandi creating high pressure in situ over central Europe, because the jet is pretty much uninterupted to the North we cannot get any retrograde blocking until the flow weakens - which is north of day 10- Past that the 00z OP tried to develop a split jet allowing a large element of amplification with a big modality swing in the AO from neutral to negative, the problem being that at that distance resolution is poor & the mean doesnt support such amplitude. The mid term forecast is therefor a continuation of mildness from the west with perhaps enough amplitude in the initial high to creep some colder continental flow into the SE as highlighted by MHugo on twitter ref lowering theta E temps ( otherwise 'coined' as faux cold ) Personally I dont think it will make it this far west as the global 60N zonal mean has increased every day towards an outlook that has more than 50% of the members of its mean over the long term climo ave CFS long term goes on to increase this into Jan ( but it is volatile ) So Why did I ( & the NW team perhaps ) go for a 'front loaded winter' - what does it mean ? For 'ME' I dont really have any interest in the teleconnections per say, that is simply because they rarely deliver any success in terms of forecasting other that when the major player ENSO completely bulldozes the NH pattern with a super Nino- What I do follow though is the zonal wind (u) @ 10 HPA across 60N - that gives us a real time framework of where the vortex is in terms of (u) zonal component & if its weak some guage of the meridional component- Its also the end result of all the trop forcing on the strat - 'the sum of all' The ECMWF compiled a data file of All zonal wind speeds back to 1957 called ERA40 & then redid them at a better resolution called Interim ERA for 1979- 2015- Whilst the data is not publicly available the key element from this is the climo line that this dataset produced to give us a steer from Nov-March where we should be on the zonal winds. ( I would love a breakdown though of the DJFM seasons though to correlate to our CET & AO/NAO couplet ) There are some key dates & info in climo ( see below ) that we should really get to know as well as records of peaks speeds & lowest speeds- for instance surprise surprise 2015 set many 'day' peak records & yesterday Dec 1981 was the lowest record - again think about that month in the context of blocking. So key dates.. - all speeds are zonal (u) wind- December 1st sees a climo ave of 30 M/S westerly ( propergating eastwards ) December 25th sees a climo ave 'peak' of 38 M/S - ironic that its xmas day - so from a winters perspective that period from about 20th -30th the NH is at a time that will have the least amount of blocking. January 15th- Feb 1st is the biggest reduction of the zonal wind across winter as the PV starts to breakdown Feb 20th onwards sees the windspeed at less than 50% of the December peak - Which is why traditionally our cold spells do come around & just after valentines day ... 2015 /16 had 3 peak record dates 07th dec -55 M/S 01st Jan -65 M/S 23rd Jan- 73 M/S - the highest ever zonal windspeed ever recorded in the ERA interim dataset. lowest was a reversal after warming at -30M/S in late Jan ( not aure what year poss 2009 ) Interestingly part of the reason why this years vortex has been slow off the mark is from the super Stratospheric Warming in early march - where the zonal wind speed dropped to -28M/S here was the warming at the start- the official SSW classification date IIRC was 4th or 5th... So we have an idea of why The zonal mean is important for forecasting - Whats important here ia equating the average wind speed with what you would 'expect' to see in the NH in terms of blocking- so December especially @ peak would have NO HLB ( 30-35 M/S ) & 1 maybe 2 max MLB- whether that be - -EPO/+PNA/-NAO/-POL...... The AO would be slightly positive 0 -+1. Whilst there is no pier reviewed paper you could then work on what a 2 wave pattern might look like in terms of being available - perhaps 0-10 M/S & a full 4 wave pattern would ve a reversal of zonal winds. so why a front loaded winter? On the 22nd of November we had a zonal speed of around +18 M/S & was presented with that high beginning to ridge NW from the UK At that very point every single GFS strat ensemble had total agreement on the windspeed dropping to a record breaking -5 M/S ( Easterly ) on the second of Dec - This against the backdrop of record breaking Neg OCT AO & the record breaking SAI for Oct, plus the below ave Nov was enough to convince me that the high would retrograde NW, so anyone thinking my forecasts for retrogression was bias to cold or non rationalised thinking would be incorrect- here was the chart - GFS ens in green From that very date ( 20th ) to today the 6th & importantly CONTINUING the Ensemble suite has gone from total agreement of a -5 easterly to quickly moving away from that figure to a varified figure on the 2nd of +12 M/S - a net change of +17 M/S - which in terms of our little patch has been the difference of retrograde or in the case now - to much positive eastward movement & SW winds- This in itself isnt the end of the world, however the following forecast for the next 5 days is a rapid increase to about 38 M/S - we have then breeched the average line & heading skwards towards 2015 ! This is TODAYS - start point is 20.5 M/S The ensembles have been trending worse & worse daily- Post peak in day 6 there is a small dip then the 10-16 day repeak at 40M/S. Which will ensure theres no COLD scandi high- it will be a positive AO - Of course the ensembles could backtrack - but generally the reversal of fortune is only apparent when predicting reversals, when they go for a very positive mean then they usually dont backtrack. The reason this is so bad is if we peak over 40 it ties in with late Dec & will have a lag of at least 2-3 WEEKS if theres a warming- So thats why theres so much annoyance.. the next 5 days will varify however if 5-16 come close you can write off any proper HLB until Mid jan is we get a SSW- **INFACT WE ARE NOW HEAVILY RELYING ON A SSW TO RESCUE OUR WINTER** we are left with a low amplitude 1 possibly 2 wave pattern - heights up to 70N if were lucky- suggested locations - Western pacific & Central Europe This means my forecast would be revised to nothing of any snow note for England other that maybe 1/2 very transitory events between now & Jan 15th- Scotland maybe 3-4 No sustained cold - with the exception if were lucky, of the good ol 'faux cold' -- I suspect that all the Glosea decent blocky runs were in response to the weakened zonal flow, now as the reality hits you will note the signal has been changed to bimodal - & when it next runs in a week or so If the forecast above has landed then it will be 1 way traffic- cheers s
  29. 74 points
    WINTER 2016/17 FULL REPORT No. 10 WITH JANUARY 22nd INPUT Please note I am still learning how to cut and paste various types of charts into my posts so please bear with me as I increasingly use these in future reports. A Review Of The Last Week: In my last full weekly report (on page 269 of this thread) I was commenting on just how busy it had been with nearly 100 pages in the week to last Sunday. Since then it has turned increasingly quiet – surely I didn’t bore you all into submission? It is due to yet more disappointment with far less promising recent model output. Well, I will do my best to add a little cheer to the downbeat mood as there are still a few interesting possibilities. I’ll attempt to redress the balance of a lack of posts on here with my longest one yet. If you think that you’re suffering from model fatigue, you will be after reading this!!! On Friday I was exchanging PMs with another member. I had been wondering why even some of the stalwart posters had deserted the model thread. The answer, I was told, is that many of you guys had gone over to the politics thread. So I had a quick look and there you all were! Although I take quite a keen interest in politics and current affairs, I do not wish to be drawn into debates on any social media forum. There’s a real danger of one muddling up the two threads and posting ones views here on the Winter model thread. Perhaps along these lines: The 18z GFS T+240 (D10): Donald J Trump says that the UK will definitely get snow in February. The 12z ECM T+1632 (D68): Britain will trigger Article 50 - bound to verify. The 12z UKMO predicts a hard Brexit but then a general thaw but we’ll need more runs and a greater consensus with other models. GEM fires up the Jet Stream straight into Brussels. The JMA shows cold air advection into Scotland as Nicola Sturgeon ponders a second Scottish referendum. The CIA (not the CMA) forecasts a huge undercut by Mexicans as they build that wall. Meanwhile NAVGEM predicts a victory for Marine Le Pen but their op run is a big outlier. The GEFS mean (really mean) shows the European cold block strengthening while the EU weakens further. Despite global warming, all hell will freeze over. The west based -NAO just about makes it to the White House. Moderators send many Remainers to the moan thread. I had better get back on track before the moderators send me into oblivion too! Last weekend we were just seeing the end of the brief Arctic incursion. The models were mostly showing a quick progression to a more Atlantic influence with HP re-establishing itself just to the south or south-east of us. I felt that the strength of the European cold block had been grossly underestimated. I suggested that the fronts across the country would not only stall but we might also see at least a week with a “continental drift” with the cold moving steadily back across the country from the south-east. I did say that a milder outcome was still “probable” beyond D10 but that there were several colder possibilities. I did not expect to see some of the models, led by the ECM, start to hint at an easterly again for several days in the D7 to D10 range, which brought rather more interest to the forum before that option disappeared too. I thought any Atlantic influence would be delayed, perhaps with a messy transition, with a more “zonal” pattern being cut short, provided that further colder options start to show themselves at the other end as we move into February. I did not look beyond D10 (now D3) I am not trying to score any points here (that’s not my style) but there are occasionally still times when good old fashioned past experience can have its place amongst all the sophisticated tools available today. The models, particularly the GFS and GEM (IMHO) can have a tendency when they pick up on a signal for a broad pattern change to be far too progressive in showing those changes, especially when it is a change from cold to mild. When HP moves across us very slowly following a cold incursion, it often allows the cold air to stagnate over us. The very blocked Atlantic (almost entirely MLB) has been slowing everything down for most of this Winter. Even the well forecast (in terms of timing – not duration) zonal spell between mid-December and Christmas (which was briefly a strong and fast moving flow producing two named storms) was ground to a halt with HP reasserting itself very quickly. Even then, we had to wait another two weeks to see our first cold snap of the year. The cold to our east became entrenched and the receding Arctic cold over the UK was still very close to us. In fact it never left the south-east before returning north-westwards. I produced another (briefer) post on Wednesday (see page 276) where I demonstrated that the predicted change to the Atlantic influence was being delayed even further. I highlighted the unusually mild weather throughout much of the USA with much weaker thermal contrasts than normal for mid-Winter (between their east coast and the western Atlantic) which was partly responsible for the continuing sluggishness of the meandering Jet Stream across the Atlantic. It now looks like there will be a further delay (perhaps until later this week) although the models are in disagreement on the timing but they all show us warming up eventually – I’ll look at this shortly (below). There are, of course, numerous examples in the past of seemingly deep cold settled conditions over us being blasted away at break neck speed but most of these occur when the Jet Stream suddenly strengthens and starts to move directly over us and right through into much of Europe. On other occasions, a small change in the position of the HP, can allow for much milder Atlantic air to come in “through the back door” with the central Atlantic flow moving northwards, eastwards and then returning southwards again. The Current Position: The European cold block has lost some of its potency but may still put up a bit more of a fight. I have been studying the depth and extensiveness of the cold for the last few days. While many on this thread only ever seem to get excited when the chances of snow appears in the outlook (and I’m a huge snow lover too) there are many other fascinating aspects of the weather to look out for, especially in the winter months. The following Meteoceil archive charts show the minimum and maximum surface temperatures over northwest Europe during the last four days: Jan 18th Maxima Jan 18th/19th Minima Jan 19th Maxima Jan 19th/20th Minima Jan 20th Maxima Jan 20th/21st Minima Jan 21st Maxima Jan 21st/22nd Minima Jan 22nd Maxima Jan 22nd/23rd Minima Current European Surface Temperatures - the 3 charts below (vertically on the left) are "live and update frequently - so come back and check for the most recent changes http://www.meteociel.fr/cartes_obs/temp_eur2.png Current European Surface pressure (1 mb pressure gradients) Current European Surface pressure with Fronts (4 mb pressure gradients) http://www.meteociel.fr/cartes_obs/pression2_eur2.png http://www.meteociel.fr/fronts/index.php (link for latest chart) Current European Satellite Imagery (this is a live chart that updates every few minutes) http://neige.meteociel.fr/satellite/anim_ir.gif Although the cold is less intense than it was a few days ago, the days have warmed up far more relatively to the nights. A wider area has been seeing maxima above freezing. The interesting bit is the huge diurnal ranges which are much more reminiscent of mid-Spring than mid-Winter. The low sun in mid-January just about has enough strength to warm the surface and a very shallow layer above it in calm conditions. The expression used rather too often by a few TV weather forecasters is for temperatures “to fall like a stone” when it might, for example, only be from 8c to 2c over a 12 hour period. Well, with this cold pool that description would be spot on. Parts of central and northern France, for example, have fallen from late afternoon values of around +7c to +10c to well below freezing just after dusk or less than 3 hours later. The final minimum values have often been well below -10c. This shows that there is plenty of cold left there. Then take the last 2 days down here in Exmouth (I live just over 1 mile inland from the coast but there was a gentle “off-shore” breeze). On Friday it was clear with a max close to 7c in the afternoon sunshine but by mid-evening (about 4 hours later) it was close to -4c. It clouded over later in the night and the temperature had risen to just above freezing by dawn. Saturday was overcast but the maximum was only 2.5c here and with much of the West Country remaining below 3c. This also demonstrates the depth of the cold. Overall, across much of Europe and southern UK, the dew points and relative humidity have been very low during recent days and the air has been particularly dry. In the south-west there was just enough moisture in the air under the thickest cloud on Saturday afternoon to produce a few snow grains – interesting but insignificant. At the time of writing this part of my report (0800 Sunday) I see that the NetWeather radar shows a few showers moving into the south-west, mostly of rain or sleet near the coast but with a little snow on Dartmoor and a small area of freezing rain in central/east Devon. Ahead of this, I see that an area of much more wintry precipitation has moved slowly north-north-eastwards into Wales and is spreading into the West Midlands where it is falling as snow (the first chart below shows the trough associated with all this). Another area of wintry precipitation is over southwest Scotland with snow in the Glasgow area (see the first chart below with the old cold front there pushing back northwards). This would seem to be the first stage of what might be a very messy break down. Slightly less cold air has now moved into much south of Devon and Cornwall but this is mostly due to a light south-south-westerly breeze which is now “on-shore”. The skies have cleared during this morning again and I think that the deeper cold air to the far east and south-east will drift back westwards during Sunday evening, especially if the flow backs very slightly to just east of south. That shallow area of LP to the west looks like it might fizzle with its fronts stalling or even slightly undercut the ridge to the east. It is not a significant feature and it’s what happens from Monday onwards that should be much more important. Now who said that this is boring weather? The main point is that the cold might be less intense and less widespread than it was just a few days ago but it is nevertheless still an entrenched cold pool that will take some shifting. If anything, the Euro minima on Sunday morning were somewhat lower and more widespread again. It may well take several pushes of milder air to shift it all eastwards. The current Met Office Fax Charts show the very short term position: 0z – valid 0600 Sunday 12z - valid 1800 Sunday 12z - valid 1200 Monday 12z - valid 0000 Tuesday UPDATE at 1600: I have just noted on the “live” European satellite imagery (see the chart above) that the LP area over the Med is starting to exert its influence again more strongly. Look at the push of cloud north-westwards. The HP ridge extending towards south-east England also seems to be strengthening. This does look like (at least temporarily) a renewed push of the European cold block into the UK. The Week Ahead: As I said, although the last few runs from all the models indicate a broad pattern change during this week, the timing and the transition is still very uncertain. The east and south-east of the UK may well hang on to the colder air until quite late in the week while the west is more likely to see milder air several days earlier. It is possible, that a temporary battleground could become established over central or eastern parts (stronger than this morning’s one over the West Country). Remember, with north-west France still cold or very cold, even a southerly airstream with south-south-easterlies will continue to draw in some pretty cold air. So a little leading edge snow is more than possible and something more significant cannot be ruled out completely. Let’s look at the cross model output for mid-week. These are D3 charts for 1200 on Wednesday, January 25th (with the T+ times adjusted for an exact comparison): GFS 12z T+72 UKMO 12z T+72 ECM 12z T+72 GEM 12z T+72 NAVGEM 12z T+72 JMA 12z T+72 GEFS ensemble mean T+72 Met O Fax Charts 0z T+84 GFS 12z T+72 Euro 850s ECM 12z T+72 Euro 850s GEFS ens mean T+72 Euro 850s GFS 12z T+72 Euro surface temps GFS 12z T+72 USA surface temps GEFS mean ens 12z T+72 Jet Stream Next Weekend: Now let’s look at all the same charts at D6 for 1200 on Saturday, January 28th: GFS 12z T+144 UKMO 12z T+144 ECM 12z T+144 GEM 12z T+144 NAVGEM 12z T+144 JMA 12z T+144 GEFS ensemble mean T+144 Met O Fax Charts 0z T+120 (last available) GFS 12z T+144 Euro 850s ECM 12z T+144 Euro 850s GEFS ensemble mean T+72 Euro 850s GFS 12z T+144 Euro surface temps GFS 12z T+144 USA surface temps GEFS 12z T+144 Jet Stream London 2m Temperature Ensembles 0z January 22nd to 5th February This very useful ensemble chart highlights the current uncertainties in the model output. Both the NCEP and ECM start off above the mean with many of the ensemble members considerably lower. The mean only slowly rises and is still below 5c up to D5 which looks to be close to the current UKMO model output with the cold block hanging on for longer. The NCEP remains a mild outlier for much of the remaining period. The ECM remains closer to the mean with a slower warm up after D6 but even that becomes a milder outlier from D7 to D10. The mean only really shows temperatures recovering slowly to closer to average levels. This is largely due to nearly half the ensemble members showing much colder conditions persisting well into week 2. This definitely does not suggest that a strong Atlantic push is a forgone conclusion and the next week will be a really fascinating one to watch for developments. A Brief Look Further Ahead: One of my golden rules is not to look at detailed output much beyond a week ahead when the models become less reliable as they tend to explore various options based on very small changes during week one. This applies even more so in the usually much more changeable Winter months, especially when broad scale pattern changes are indicated. This “Winter of Wildcards” has already served up some big surprises, although most of them have not been favourable for prolonged cold and snow. It is far better to take a more general look at the broader pattern and the background signals. There is still a chance that the European cold block may not be pushed away too far east. This now seems unlikely, especially if the much stronger Jet Stream predicted into week 2 runs straight through the UK. So, if we do see a much more unsettled period under Atlantic influence, how long will it last and will there be further opportunities for colder weather again? The last change from blocked to more zonal was originally predicted by all the models to last for at least two weeks or longer. Very few of the ensemble members suggested a quick return to a blocked pattern again. Then, they finally picked up on the signal and the unsettled Atlantic surge ended after less than 10 days – even less in the south. I have seen very few updates and opinions recently from our more seasoned posters (perhaps they are also suffering from model fatigue) in respect of the anticipated strength and path of the Jet Stream, the position and strength of the PV, upper wind strengths, prospects of any amplification etc for the next two weeks and into early February. This includes the ensemble charts from Knocker and John Holmes. I invite you all to update us with your expert analyses. I have seen the excitement building in respect of a possible SSW (Sudden Stratospheric Warming). I know that the main posts on this subject are often confined to the strat thread but this is also very much model related in terms of the prospects for the last third of this Winter and into Spring. It will be advisable for the rest of us, not to pin all our remaining hopes on a full on SSW that propagates quickly down to the surface. Even some warming can have quite an impact on the broader pattern and set up. It is also very possible to see cold (and snowy) spells develop without any SSW assistance. Will we see a third Winter month in a row with a mostly blocked Atlantic? Could this produce more HLB rather than incessant MLB? I will not be giving up on this Winter until February 28th! I have noted that the latest monthly update on ENSO (El Nino Southern Oscillation) conditions was published by NOAA and CPC this week on January 16th. Here’s the summary: “…..ENSO Alert System Status: La Niña Advisory. La Niña conditions are present.* Equatorial sea surface temperatures (SSTs) are near-to-below average in the central and eastern Pacific Ocean. A transition to ENSO-neutral is expected to occur by February 2017, with ENSO neutral then continuing through the first half of 2017. * Note: These statements are updated once a month (2nd Thursday of each month) in association with the ENSO Diagnostics Discussion, which can be found by clicking here.….” The link to the full discussion: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/lanina/enso_evolution-status-fcsts-web.pdf and a further link to an interesting paper from the same site: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.pdf Most of the last few months have seen either very weak La Nina or close to neutral conditions. This update shows that the most recent weak La Nina will again return to neutral. I know that in extremely simple terms, an El Nino Winter makes an SSW event more likely and a La Nina Winter makes it less likely. I assume that very weak or neutral conditions do not make an SSW event more or less likely. How far in advance can particular ENSO conditions have some sort of an impact? I would assume that the recent and predicted changes may be too late to have much of an impact? I’m out of my depth now, so I’ll leave it to the likes of Tamara, Catacol and the other teleconnection experts to give their views. Now on to my routine coverage. Arctic Sea Ice News and Analysis: The last full monthly report was published on January 5th. This is a fascinating read and includes a review of the whole of 2016. Please note that the current ice extent map and the comparison chart to the mean are updated daily and are always of interest. Here’s the link for the latest updates: http://nsidc.org/arcticseaicenews/ This chart shows the current extent of the sea ice (as on January 21st) in relation to 30 year means. Source: National Snow and Ice Data Center (NSIDC) The “rate of recovery” during December was very close to a record but, despite this, the overall ice extent is still at record lows and remains just below the previous low set during Winter 2012-13. Overall ice growth stalled again about a week ago but has resumed growth again in the last few days - at least in the Baring and Kara Seas which should see some rapid growth due to some deeper cold setting in, as is demonstrated later in my Svalbaard temperature review). Arctic Oscillation (AO) 14 Day Ensemble Charts (updated January 22nd): The Arctic Oscillation is currently close to neutral but trends very strongly positive during the next week before falling sharply again into week 2. Then several members go negative while the others trend higher again. This demonstrates the very uncertain model output but overall is reflective of practically no HLB. Note for newbies: The AO index reflects the amount of HLB in the Arctic. A positive +AO reflects very little HLB and a strongly +AO reflects no HLB anywhere in the Arctic. A negative –AO reflects some HLB and a strongly –AO reflects substantial HLB with more intense high pressure and/or more extensive HLB in various parts of the Arctic. This index produced by NOAA is based upon GFS output and will fluctuate in line with that model. Although ECM produce similar data based upon their own output this is not one of their “free-to-view” charts for public consumption. Here's the link which will update automatically with daily charts: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml ...and here’s the current chart: North Atlantic Oscillation (NAO) 14 Day Ensemble Charts (updated January 22nd): The NAO is currently trending from slightly positive to slightly negative later this week before returning to around neutral (with some members still slightly negative and some slightly positive) during week 2. Again a mixed picture reflective of the rather uncertain GFS modelling. Note for newbies: A neutral NAO index reflects the close to average state of the mean sea level pressure patterns or the “climatological” norm in the North Atlantic. This would equate to the anomalous high pressure in the south, particularly around the Azores and low pressure stretching from off the eastern USA seaboard in a wide band running north-eastwards to the east of Newfoundland, east of Greenland and through Iceland. A positive +NAO occurs when these patterns are stronger than usual (eg: the Azores high is more intense or more widespread and/or the Iceland low is deeper or more widespread than usual). A negative –NAO reflects a weak Azores high and/or less intense Icelandic low pressure. A strongly –NAO would reflect a reversal of the normal patterns with relatively low pressure in the Azores and high pressure further north towards Iceland. A “west based –NAO” (talked about recently) is when the pressure is higher than usual in the western Atlantic such as around the Newfoundland area). An “east based –NAO would indicate higher pressure than usual in our part of the Atlantic. This index produced by NOAA is based upon GFS output and will fluctuate in line with that model. Although ECM produce similar data based upon their own output this is not one of their “free-to-view” charts for public consumption Here's the link which will update automatically with daily charts: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml (click on the small chart there) ...and here’s the current chart: MJO Ensemble charts: Here are today's MJO ensemble charts for the big 4 (all updated on January 22nd) + Kyle MacRitchie’s modified chart (by request following last week’s discussions) with the live links below should you wish to check any future changes. UKMO (7 day forecast): ECM (14 day forecast): NCEP/GEFS (14 day forecast): JMA (9 day forecast): UKMO: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ukme.shtml ECM: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml GEFS: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml JMA: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/jman.shtml Kyle MacRitchie and the link: https://weatherandvines.com/?page_id=140 + his explanatory notes and further guidance: https://weatherandvines.com/?page_id=128 COMMENT: The big 4 are more in line than they have been for many weeks. They start the MJO off in phase 1 at good amplitude, then move it through phase 2 (UKMO reaches phase 3) before moving into the COD (circle of death). Kyle’s chart is different, moving the MJO at low amplitude through phases 7 and 8 during the next week before entering the COD with one ensemble member re-emerging at phase 5 around Feb. 5th and progressing through phases 6 and 7 still at low amplitude. Northern Hemisphere Snow Cover: I show animations for snow cover and sea ice changes. These are produced by the National Ocean and Atmospheric Administration (NOAA). When you go to their site you can change the date range and go back over 10 years. You can change the speed and pause on any particular day. These are brilliant, very informative charts and great to play around with. I have re-set the links below to show the last 2 weeks from January 7th to January 21st but you can change these again on the site: a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA January 21st): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20170107-20170121 ....and here is their current chart: b) Animated Europe and Asia Day Snow Cover (updated by NOAA January 21st): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20170107-20170121 ....and here is their current chart: BRIEF COMMENT: Much of central, eastern and southern European is snow covered. There continues to be well above average snow cover over northern Asia and this has continued to expand southwards and south-westwards. Scandinavia is once again fully snow covered, except the far south (the high central plateaus usually have pretty complete snow cover for most of an average winter). Meanwhile, the extensive snow cover over North America has declined sharply due to the much milder conditions there. Current Arctic Regional Surface Temperatures: GFS – Northern Hemisphere Current Temperatures for January 22nd 1900 (12z – 1300 T+6): and here’s the link to live charts if you wish to view future changes (updated 4 times a day): http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=6&mode=1&carte=1 Here is my selection of Arctic Regional Temperatures: The previous readings from my last full report are shown in brackets alongside North Pole: -28c (-16c to -24c). Barents Sea/High Arctic: -12c to -20c ( -4c to -20c). Scandinavia: south +4 to -12c (0c to -4c); north -12c to -16c (-8c to -12c). Northern Siberia: -24c to -40c (-28c to -40c). North West Russia: -8c to -20c (-28c to -40c) North-east Europe: 0c to -8c (-8c to -12c). Greenland: -20c to -36c (-16c to -40c) Canadian Arctic: -12c to -32c (-12c to -36c). Alaska: -12c to -36c (-12c to -28c). Please note: For land masses I have tried to focus on readings away from the coasts and away from any mountainous areas. You can follow the trends by looking at the latest data at any time from now on. It is vital to note the time of day to take account of daytime/night time variations. So for like for like comparisons, for example the 1900 charts for each day should be available to view from the 12z (T+6) updates which are published around 1600 to 1700 or about 4 to 5 hours later. Svalbard Daily “Maximum” Temperature Forecast for 10 Days: Here are the links to the 3 Svalbard stations that I am monitoring together with a summary of D1, D5 and D9 values: Central/West Svalbard – Longyearbyen 28 m asl: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf January 23rd -13c; January 27th -14c; January 31st -15c. North-West Svalbard – Ny-Alesund: http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf January 23rd -13c; January 27th -20c; January 31st -22c. Central South Svalbard – Sveagruva: http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf January 23rd -11c; January 27th -19c; January 31st -21c. Please note that the links above will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at quite short range. BRIEF COMMENT: Temperatures have been trending much lower (apart from tomorrow which will be closer to freezing during some quite heavy snowfall) and end up around their lowest levels seen this winter (matching the 2 to 3 days in early December and very briefly last week) and down to or even below their 30 year means which has rarely be seen in the last 3 winters! This injection of deeper cold should help the Arctic sea ice extent to quickly resume its growth in the Baring and Kara Seas where it is still at record lows right now for mid/late-January. To put the above figures into context, here is a link to the main Longyearbyen site: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html This shows monthly means and actual highest/lowest temperatures recorded during this winter and goes back further. Svalbard has been seeing “maximum” temperatures often running at 8c to 10c above their long term average throughout most of 2016. This has been the pattern for several years and is reflective of the warming Arctic and record low sea ice cover. Final Comment: Despite what many on this thread seem to think, there is still plenty to interest us all! Next Update: My next full weekly report should be on Sunday evening, January 29th. It will be a good deal shorter than this marathon effort!
  30. 74 points
    CPC analogues rolled forward days 10-12 confirm the idea that we are heading towards an Atlantic ridge / Scandinavian trough solution in the last week Jan into early part of Feb... which might be useful as the models seem to be losing all coherence as we approach the business end of the winter. Relative angular momentum has peaked in the last few days and, as tendency in relative angular momentum (the rate of acceleration or deceleration) cannot be maintained forever, some negative tendency is expected in the next 10 days. Total and relative angular momentum will however remain high as a large surplus of westerly inertia remains in the atmospheric system, demonstrative of a fully coupled atmospheric - ocean circulation. That places the GWO in a quasi stationary phase 6-7 orbit for the next 10 days. Composites are a bit messy but broadly align to Scandinavia trough a deep low in the Western Atlantic. This is complicated as we are approaching a monthly change, and February's composites hold some value. But generally Atlantic attack from the south-west and re-asserted Scandinavian trough as the theme. The GFS and EC monthly and EPS MJO signals suggest the MJO to become coherent in the Indian Ocean and towards the Maritime Continent during weeks 2-3. It should be remembered that there will remain a low frequency signal for convective anomalies in the Central and Eastern Pacific as well, so the MJO projection onto the system will be altered and angular momentum will remain high. MJO composites alone of limited value and it should be stressed again that the MJO signal needs to be transposed onto the GWO. The main point to draw from this signal is that angular momentum will begin to rise again during week 3 (early Feb). This gives a stable GWO phase 7-6-5-6 type look to the pattern for the next 2-4 week period, with phase 6 being a strong attractor within the base state. Composite is very consistent and now familiar as we turn towards the back end of Jan into Feb...Scandinavian trough, anomalous ridge centred just south of Greenland. Those looking for early spring warmth in the first part of Feb may be disappointed. As wind vectors, I would be thinking NW, N and NE, allowing for a bit of westerly flow days 7-10.
  31. 73 points
    Whoah.....hang about. That can't be allowed to pass unchallenged. Do you *really* think Prof Adam Scaife - and the Hadley Centre scientists - sit in their monthly Seasonal Team meeting at Exeter and stare singularly and unscientifically at UKMO output and then dismiss everything else out of some sort of 'confirmation bias'?? The Contingency Planning 3-month document (which, stress, is a *probabilistic*, not *deterministic* outlook) is based on the consensus reached at those monthly meetings and written-up shortly afterwards. At those forums, the collective output across a number of respected seasonal modelling centres is viewed comparatively with weighting applied; and detailed areas of global forcings/teleconnections discussed. This includes output made available to UKMO from ECMWF, MeteoFrance, NCEP, plus Japan/Korea/S Africa and many others. Indeed you will often see reference made in those documents to where agreement exists between GloSea5 and "other seasonal forecast agencies/models". This isn't some cursory exercise of pulling bits of CFS off the web and comparing to UKMO products: it's a rigorous piece of scientific scrutiny with a duly critical approach applied. The fact remains that as of mid Nov, excellent agreement on broadscale pattern existed between GloSea, ECMWF Seasonal and MeteoFrance-Climate. Not dissimilar output appeared in other (less highly weighted) models such as CFS. Note that at NO point did UKMO probabilistic forecasts lean to 'very cold' categorisation: merely a higher than average chance of colder than average. Anxious that certain media types would blow it all beyond proportion to ape 2010-11, Adam blogged in detail on the UKMO website to offer context to the last two 3-monthly outlooks that were issued. To suggest Adam and his team "took eye off ball" out of some deference to an in-house model firstly ignores the cross-model support available to them at the time. Secondly, it's actually quite insulting for a guy who has published or co-authored so many peer-reviewed papers in the field of seasonal to decadal forecasting; SSW's; etc etc. Whatever has gone pear-shaped so far in Dec, I'd wager Adam could explain unhesitatingly. And by the way: with cluster 1 of today's 12z ECMWF heading into building strong +ve GPH anomalies and rising MSLP above Scandinavia with a resultant easterly flow just before Christmas, it's also too early anyway to utterly dismiss what Glosea leaned to originally.
  32. 73 points
    I am somewhat concerned that some posters are allowing themselves to be misled regarding the timing and intensity of this cold spell. There has been a continuing tendency for some to ramp up the cold and especially any possible snowfall when one or more charts hint at something quite wintry and then, on the next run, following a minor downgrade, to criticise the models. There have also been a few posters who have taken out their disappointment on others. The moderators have tried to delete some of the worst of these. Whilst I fully appreciate that the exceptionally mild winter and the occasional missed snow event has constantly frustrated many of us, we all need to remember that this is a model interpretation and discussion thread. I feel that there is plenty on offer in the coming few weeks to be excited about but we need to be patent. When I posted early last week (page 98 on 31.1.16 model thread) I pulled together a number of reasons that indicated the ”likelihood” of a prolonged cold spell. I said that the models would take some time to factor in the main changes and we would see substantial swings before they agree. If anything, I was a little surprised at the initial very swift change to colder longer term predictive charts and then, perhaps inevitable, an apparent downgrade. I do not feel that this week’s rather cold spell is anywhere near the main event. Let me explain why. I started writing this post this morning but was too busy to finish it until now. I was going to draw attention to the excellent work done by AER (Atmospheric and Environmental Research) scientists. I think some of you are familiar with Judah Cohen, one of their team and the author of their “Arctic Oscillation Analysis and Forecast” reports. The latest update was published yesterday. http://www.aer.com/science-research/climate-weather/arctic-oscillation In the meantime, I note that bryan629 beat me to it and posted the link this morning. I often look at other areas of research to get a wider view. This report is essential reading for all those following the model threads. To summarise, you’ll see that the current colder spell is attributed to the combination of impact factors including the El Nino, the MJO in phase 7 at reasonably high amplitude and the “last” stratospheric warming event – the one which started in early February and quickly petered out. They are expecting one final pulse of energy disrupting the polar vortex later this week but after a whole winter with a high energy polar vortex it seems that we will at last be rid of it. I would suggest that this is why this week’s cold is not particularly severe and some models have back tracked somewhat on next week’s continuing cold. The AER are very confident that the current neutral Arctic oscillation will be moving into a negative phase imminently (probably starting as soon as this weekend) and will stay in a strongly negative state for the foreseeable future , perhaps for 4 to 6 weeks. They expect the stratosphere and troposphere to fully couple in a negative AO state and they say that this last happened in February 2010 (perhaps one of you fellow posters would like to dig out one or two charts for that spell and show it on this thread as an analogue for current comparisons). They are also predicting further stratospheric warming influences starting within the next week and developing from there (this has been indicated on some of the models). They feel that this will re-enforce the negative AO state. The PV has split and the tropospheric vortex is predicted to push down into continental Europe. They expect the impact to be substantial with low heights spilling south into Europe. They favour winds veering into the north-east. Their only caveat is that this is all occurring very late in winter but they expect the pattern to follow in a similar way to a mid-winter SSW event. As Singularity points out, the MJO is a little mystifying. Having reached phase 7 at quite high amplitude it seems surprising that most of the models predict it’ll only be in phase 8 very briefly before returning to 0. I hope that we stay in phase 8 at decent amplitude for longer. The MJO may well have already played its part in the current major pattern changes and perhaps the other factors are now the more major driving forces in the next few weeks. So how do we interpret this for the UK? I would suggest that we may see a very temporary weakening of this week’s colder spell early next week (probably not mild and may continue cold throughout) and then a much stronger and longer lasting cooling later next week as indicated by several of the models like on the 00z ECM run. The cold should be sourced from much further north/north-east. Most of Europe should cool significantly and a proper cold pool should finally be established. Although the pattern of events seems similar in timing to those of March 2013 there are probably enough differences to make a repeat of that famous cold spell unlikely. Judah Cohen prefers the February 2010 analogy. To compensate for the lengthening days and ever greater solar energy during March, we should get much colder uppers than we have seen/will see this week. The default north-east airstream could well continue to be a predominantly dry one with showers confined to windward coasts but one would expect some disturbances and perhaps several more widespread wintry outbreaks and possibly greater convectiveness given the colder uppers. We could get up to 3 or 4 weeks of this type of weather, so surely plenty of wintry opportunities. Just how cold and how snowy is, as always, very uncertain. I believe that the models will start to take greater account of these pattern changes during the next few days. Fergie’s update yesterday was useful (always appreciated). I see that the monthly update he refers to was probably prepared several days before some of the latest factors could be fully assessed (perhaps I’m wrong here?). The broader picture is similar though. Do they take account of the AER updates? How do they rate them? Nothing is guaranteed and I do not wish to lead anyone to believe that this will happen exactly as I have suggested. It is simply my view on the broader pattern changes and their possible impacts. I feel that model watching will be very interesting indeed during the next couple of weeks.
  33. 72 points
    Yes I'm still here, just too busy with work and the like. I appreciate the kind comments though, thank you all. This autumn/early winter looks so different compared to recent years, I am impressed by the significant temperature fluctuations up in the stratosphere, not to mention the relative weakness of the Atlantic systems coming our way (apart from Storm Angus of course). I note that quite regularly in runs over the last week or two the GFS has shown a real wintry setup in the longer term, with the jet travelling way south. There's quite an arctic plunge heading into W Europe in the next few days, bit too far E for our purposes but if HP stays anchored close to us and LP going over the top, further incursions of cold air seem likely very near to us. I'm looking for signs of cold air pooling over Europe in the coming days. There has already been very intense HP last week in Russia (near to 1070mb) so if the cold air gets a real chance to settle over Europe, I think it would only be a matter of time before it spreads our way. I've a feeling in my old bones that the weather might make headlines this winter and not from rain, wind and floods as has happened so much in recent years, but "The Big Freeze" type story. I think a really cold winter is well overdue (the last one that I think qualifies as that was 1978/79). I've even beefed up my home heating in preparation! If I see anything I think looks promising in the coming days, I'll be back!
  34. 71 points
    Good afternoon gang ,its nice to be back reading all the posts again ,although i have been lurking .(Thanks to all friends on here for my much appreciated messages over the loss of my wife recently ,THANK YOU ALL ) .Its great to see that the charts are showing some Winter weather , really warms the cockles of my heart .And its the charts which keep us interested not always showing us what we want ,and i,m certain that over the coming winter there will be Prozack moments and of course STella times ,so with the Meteorological Winter looming we can look forward to 364 roughly Runs of the good old GFS ,182 of the ECM , AND HUNDREDS OF OTHERS .Looking around the Internet back last year i looked at many weather forums etc ,and found that ours is by far the best and most interesting around .In my next post i will stay on Topic ,just wanted to start with a light Hearted post today .Let the hunt for Winter Synoptics commence ,Curtain twitching ,hiding behind the settee etc ,cheers gang ,.
  35. 70 points
    There are quite some similarities to next weeks possible easterly to the evolution of an easterly in 2012, that involved a trigger low, a boundary front and snow event (12cms of powdery snow for me with a wind straight off the channel) At face value the synoptic chart doesn't look anywhere near as promising as to what was actually delivered as a snow event for some of us. But it did deliver! And whilst it was hardly exactly of Jan 87 proportions it led onto a cold easterly which albeit dry, preserved snow cover for a week with severe frosts, sub zero dewpoints and temperatues which didn't rise above freezing each day - despite clear skies and unbroken sunshine Taking just the UKMO t144 at face value as to next weeks potential.... I wouldn't be worrying at all about the evolution from there, with the cold about to back westwards and pressure rising to the NE. I remember in 2012 the GFS flapped around really badly, and incrementally over at least two to three days, backed its flat pattern further and further west. I'm not sure much has changed since then... 2012 was an example of getting the snow in and then, at the least, preserving it afterwards even if no more snow arrived. With the immediate short term already lining up snow events for various parts of the country and on the basis we can't (yet) rule out the possibility of an unstable convective easterly to follow it, who knows, there is, at the minute, a chance to top Feb 2012 (??) *Ramp disclaimer* Snow was not widespread in Feb 2012, but it still showed that a relatively limited background pattern can yield surprisingly lasting cold and snow surprises in the absence of a high latitude block - when a mid latitude scenario involves sufficient amplitude to take advantage of an Atlantic sector pattern which does not ramp up again after the initial amplification - and at the very least preserves surface cold after snow event(s) As I said a few days back, model output was set to generate my own interest at last. Its been upgrades all the way since. Based on a few years in the snow wilderness for many of us, lots of reasons to be cheerful and hopeful at the moment whatever happens
  36. 70 points
    The current projected Wave 1 displacement of the stratospheric vortex looks to be following the script nicely. During the last few days and for the next 2-3 we will see a series of unusually deep low pressure systems within a large upper trough over the North Pacific region. This leads to Wave 1 activity lagged by 14-21 days and takes us to the current projection for an unusually weak zonal wind flow throughout much of the mid and high latitudes. Both the GEFS and EC EPS are reasonably consistent on a weak westerly zonal wind at high latitudes. This extends throughout the troposphere, and you get some idea here as to how ingrained this pattern is. Looking forward, another series of deep upper low dominate the North Pacific in the 6-10 and more particularly the 11-15 day timeframe (and also +ve mountain torque during this time as well). Net result, more displacement of an already weak stratospheric vortex almost certain towards the end of November and start of December. That is peak vortex cooling season, so we are going to be totally against recent climatology at that point. The lack of any detectable influence of relatively high geomagnetic activity and westerly QBO is stark. So the key question, what happens after that in the stratosphere ? Clearly at some point, any downwelling of easterly zonal wind anomaly from the upper layers will pull down colder air. The vortex will cool. However, feedback loops may already make that cooling ineffective and ultimately may provide a killer blow for the vortex. Check out those years where cooling was delayed into December - it doesn't make happy reading for strong vortices in January !
  37. 69 points
    WINTER 2016/17 FULL REPORT No. 7 (PART 1) WITH JANUARY 9TH INPUT Please note that some of the charts that I refer to in this post are through “live” links which update periodically. So, if you are reading this a few days or even hours after publication (on Monday, January 9th at 1945), some of the charts may already have updated. My comments relate to what the charts were showing at the time of this posting. I am just starting to learn how to cut and paste charts into my posts so please bear with me as I increasingly use these in future reports. @Mucka thank you for all your help with these. I am still having some problems with getting charts to freeze in time and I will be getting further help from another member in the coming days. I have decided to split my reports into two parts from now on. One of my main features is always on Judah Cohen’s latest Arctic Oscillation report. These are always published around 2300 on a Monday evening which means that my report posts are delayed until around midnight and editing continues for at least another hour after that. So, the Judah Cohen analysis will be in “part 2” and the main “part 1” report, with my other regular features, will go live much earlier in the evening. I hope that this will be useful for everyone and it will certainly allow me to get to bed at a more reasonable hour. My Take On The Current Model Output And My Reporting Dilemma: As some of you “may” have noticed, I like to produce occasional but long reports, too long I hear some of you say but this presents a problem. Most posts on the MOD are directly responding to a particular model run and in a specific time frame. The preparation and much of the textual commentary in my reports are spread out over 8 to 12 hours (in between my business commitments). The model output can swing hugely over this short period potentially rendering some of what I say as out-of-date when my post goes live. I usually make more general points and take an overview which takes some account of the fluctuating output. If I make a direct comment on one or more of the models I do usually quickly check for any recent/concurrent changes. After last night’s 12z (UKMO & ECM) + the 18z from GFS, I was thinking that I will go with my usual cautiously optimistic approach and managing expectations but this morning, following something of a downgrade, I was thinking of being more upbeat. I am a self-confessed coldie and I love snow like the majority of us in this forum. So, just for a change, please permit me to indulge myself. I am releasing the safety belt and will put a very positive spin on things without any undue ramping. Barring some sort of last minute calamity, we can expect the Arctic cold to move into the UK later on Wednesday and through at least Thursday and Friday. It appears that almost anywhere could see at least a little of the white stuff. The big 3 models have “mostly” been showing quite a clean north to north-north-west flow. There does seem to be potential for one or two small disturbances forming within the flow and as, most of us appreciate, any minor troughs cannot usually be pin-pointed in terms of position and timing until we are much closer to the event (D1 to D2). As @Nouska pointed out as early as last Thursday evening (before anyone else, I think) the conditions may well be ripe for possible Polar Low development, probably from late Thursday and through Friday. With the 500mb temperatures probably still below the key -40c threshold and easily lower enough 850s (update: may be more marginal) the potential still seems to be there. Others with more experience than me on assessing the upper flows can comment on the finer details and requirements. Overall, there is plenty to keep us occupied during the next 5 days and shorter term model watching will be extremely exciting. Now, there is still much uncertainty over the longevity of this cold snap/spell as well as the intensity. I have some good news on the latter in my Arctic temperature analysis later in this report. For a few weeks now, we have seen a quite extraordinary period of model uncertainty with some wild swings, upgrading, downgrading, lack of consensus and sometimes utter confusion. I have commented extensively on this in my last few reports. As always with this wonderful science, there is a whole array of possible outcomes. I shall attempt to group these into four broad categories, starting with the least attractive for coldies: i) The cold snap breaks down quickly and the Atlantic piles in: The GFS 0z operational run output indicated a rapid end to the cold snap, perhaps as soon as Saturday, with a strong westerly or perhaps a south-westerly being pushed in on a much more zonal flow on a powerful west to east jet stream. This being supported in part by the strengthening upper flow. The run was later proven to be a big mild outlier but is a possible outcome. The GFS is often very progressive when it decides to bring in a zonal flow. I feel that it completely underestimates the massive strength of the central European cold block. Although the low heights over Scandinavia (which help to bring in the Arctic airstream in the first place) may displace the deepest cold slightly eastwards for several days, the Arctic cold will spread down over much of western mainland Europe with some pretty widespread snowfall. By next weekend, our European neighbours will have temperatures at or below freezing over a wide area. History tells us, that even in the most zonal of Winters, if these blocks become established, they rarely give up without at least a fight. This could leave us right in the centre of the battleground for a few days. ii) The cold spell breaks down more slowly with a very mixed period ahead: Carrying on from what I just said above, the cold snap or spell (it might be useful if we could actually come up with a time definition of each to prevent ambiguity) might last a little longer, perhaps well into the following week (say to around D10 to D12 or around January 20th for example). It’s surely more likely that once the cold is established, that it will take a while to shift and perhaps several attempts at milder incursions to finally clear it. Some of each of the recent models’ ensemble members suggest this type of scenario. There could even be some fronts stalling producing some additional boundary edge snowfall before the milder air takes hold. Thereafter we might see a return to climatology, although with all the mixed and seemingly conflicting northern hemisphere signals we have seen recently, this is a far too general term and rather a cop out. For now, let’s take it in its more literal sense, with predominantly average to mild conditions but with some colder interludes. iii) The cold spell temporarily breaks down but with renewed cold spells to follow: I’ve seen a few posters mention more than once, that the D6 to D10 period might be critical in deciding the outcome of the rest of the Winter. Whilst it might be crucial in terms of the next couple of weeks through to late January, these types of dismissive statements are almost always wide of the mark with no evidence provided at all to back up this emotional viewpoint. In this scenario (as with all the others but a special point to be made here), we have to weigh up some of the uncertainties of the background signals, any areas of warm air advection into the Arctic, the degree of any amplification, the continuing strength and position of the polar vortex, the strength and direction of the jet stream and will it split, the development, speed and track of certain short wave activity and various other factors. Following the two North American cold snaps/spells (the first a very cold one) we are about to see the opposite with an extended period of widespread warmth in that continent. Although other factors are also involved, it occurs to be that with greatly reduced thermal contrasts (east US and west Atlantic) that this might well lead to an abrupt weakening of the jet stream with some favourable (for blocking and more likely colder patterns) downstream consequences for us. Probably a rather too simplistic assumption. I was also delighted to see @Tamara in her post yesterday, to be able to report more optimistically on the recent changes and movements in the Pacific at last allowing a greater “likelihood” (not a definite forecast) of rather more enhanced HLB as we proceed though the second half of January and into February. Just a little comment here – a few of you guys seem to think that Tamara takes pleasure in destroying all hopes of possible colder weather patterns developing. This couldn’t be further from the truth as she is a Winter coldie and loves snow like the majority of us. So, please be far more respectful of her posts and let’s avoid this bickering over the relative merits of teleconnections, whichever side of the fence that you sit on. Right, no more on disrespectful behaviour in this report – there is far too much exciting weather around to discuss anything else! I feel that there is enough evidence to suggest that even if we have a temporary warm up that there will be plenty of further opportunities for more cold spells during the remainder of this Winter. I firmly believe that January, at least, will turn out to be a below average month for both temperature and rainfall. Just how extreme, is still very much undecided. iv) The cold continues and develops into a prolonged and memorable period of cold: While my third scenario is the one that I currently favour, let’s really indulge ourselves now with a little FI ! In my last few weekly reports I’ve drawn attention to how unusual the weather patterns have been throughout most of 2016. Record strengths and weaknesses in the PV, record low Arctic sea ice build-up (see later for an important update) and a highly anomalous belt of high pressure close to our shores or right over us, just to name a few. Recently, we have seen some extreme cold developing over central, eastern and southern Europe with a widespread pool of very low temperatures. The imminent Arctic outbreak is quite a potent one in comparison to anything that we have seen in the last couple of Winters. So, unlike almost anything since March/April 2013, we at last have some very cold pools close by to potentially lock into. It is quite possible that the Atlantic will not succeed in shifting the cold block to our east. It may not matter initially if we do not lock into this block. As long as it holds back any milder weather, we can retain the cold over us for longer. We might be open to one or two more Arctic incursions to top up the cold. Some of the model ensembles have shown high pressure hanging on close to our east (I’m not referring to a Scandi high right now). Our own cold might be allowed to stagnate right over us. I can recall many times in the 1960s and 1970s when we drew in a south-easterly off a cold continent and these conditions persisted for a long while. With near record cold over southern Europe we could actual maintain pretty cold conditions even on a more southerly flow with the winds coming in on a south-south-easterly having crossed a quite icy France (within a week or so). I appreciate that it can only take a very small veering of the flow to pull in some much milder air from a more tropical source. As I said earlier, this type of pattern can also produce a prolonged period where we are in the centre of the battle zone. Between the cold to our east and the mild and wet conditions to our west. Here, the east can remain cold or very cold while the west can often be on the mild side (not so good for me down here in Exmouth or our friends over in Ireland). Some of our greatest blizzards have developed in southern England on the narrow margin between the two when we have seen undercutting where mild air is unable to penetrate the cold block and rides over it producing some very heavy snowfall. The blizzards are quite rare events but more localised decent snowfalls are much more frequent (or used to be). So far, I haven’t mentioned the possibility of us seeing a proper easterly set itself up and drawing in some of the extremely cold air. The ECM has consistently hinted at this evolution towards the end of a number of runs. Mostly recently (on the 0z) just failing to achieve this. Some of its own as well as other models’ ensemble members still lead us to an easterly flow. So, this cannot be discounted even if the probabilities are still quite low. The longer the cold block remains close enough to us, the greater the opportunity for this type of evolution. There are also one or two other more positive hints for coldies. There are signs of the MJO at last coming to life and as the likes of @Singularity and @nick sussex tell us, if this cycle gets us into the important phases (7,8 or 1) at the right time, then this should assist in favouring or enhancing greater HLB. I’m not going for scenario four, which is probably rather more in the way of wishful thinking. In this unusual Winter none of the four can be ruled out with the second and third scenarios much more probable than the two extremes. Why can't that anomalous area of high pressure set up and stick around in a much more favourable position? I am going to write a warning to myself to stop the ramping and to manage my own expectations! The message is that there is plenty of potential and a lot of exciting model watching ahead. Compare all this to what we saw for much of last Winter. Now you can all criticise me! Update 1 at 1630: Whilst writing this report, I just had a quick look at the 12z. GFS, which was looking to be going for scenario (i) but ends up closer to scenario (ii). UKMO looks much more like scenario (ii) but only out T+144. Both could still hang on to enough surface cold to get closer to scenario (iii) but a less cold interlude is indicated. I’m not excepting any model to go all out for scenario (iv), at least not at this stage. It is best to expect more quite large swings. It’s looking like FI was yesterday!. Update 2 at 1830: Several more ensemble members and the GEFS mean suggesting a possible easterly. It would be highly ironic if the deep cold pool was displaced a lot further east before the pattern develops. It might still, however, bring back the cold westwards if it becomes a persistent new pattern. Update 3 at 1900: Gosh, I was wrong – the ECM12z has chosen my scenario iv. Even though I allowed myself some bullishness, I did not expect this type of evolution to show this far out but they have been pretty consistent. This is their patch, ie: home territory – does this give them an unfair advantage? So at least you can blame them if it doesn’t verify! Who will be right? Dr Judah Cohen’s Latest Arctic Oscillation Report: As I said earlier, this will now appear in part 2 of my report, probably around 2300. Now I move on to my regular features. Arctic Sea Ice News and Analysis: The latest full monthly report was published on January 5th. This is a fascinating read and includes a review of the whole of 2016. Please note that the current ice extent map and the comparison chart to the mean are updated daily and are always of interest. Here’s the link for the latest updates: http://nsidc.org/arcticseaicenews/ This chart shows the current extent of the sea ice (as on January 8th) in relation to 30 year means. There are two extraordinary points to make here. The “rate of recovery” during December was very close to a record but despite this the overall ice extent is still at record lows and remains just below the previous low set during Winter 2012-13. Perhaps this is not so extraordinary, as there was highly likely to be a strong recovery from such a low base during November. I have been speculating during the last few weeks as to when (and if) 2016-17 will finally overtake 2012-13. I thought that it might have occurred by now but with temperatures up there much lower now than this time last January we should see a further rapid increase and may be we’ll be there by next week. Arctic Oscillation (AO) 14 Day Ensemble Charts (updated January 9th): The Arctic Oscillation, which is moving from positive to neutral or slightly negative this week goes mostly positive again during week 2 but with a few ensemble members remaining negative and trending down at the end. CAUTION: this is in line with the current GFS model output (probably today’s 12z) but is liable to further fluctuations in line with changes in that model’s output. It does not reflect any decisive swing to greater HLB but does paint a very uncertain outlook. Here’s is the link for future reference: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao_index_ensm.shtml ...and here’s the current chart: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.sprd2.gif North Atlantic Oscillation (NAO) 14 Day Ensemble Charts (updated January 9th): The NAO is also mixed and rather uncertain, trending from positive towards neutral with some members going negative next week. This trend may be slightly reflective of GFS modelling higher pressure a little further north than usual (in our vicinity). Both the AO and NAO reflect the very mixed GFS output. Here’s the NAO link: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gif ...and here’s the current chart: http://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.sprd2.gif Please note that both the AO and NAO charts I show are based on GFS ensembles so are indicative of their modelling and not the ECM and UKMO output. MJO Ensemble charts: Here are today's MJO ensemble charts for the big 4 (all updated on January 9rd) with the live links below should you wish to check any future changes (hope they work properly!). UKMO (7 day forecast): http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/UKME_phase_23m_full.gif http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ukme.shtml ECM (14 day forecast): http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ECMF_phase_MANOM_51m_full.gif http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ecmm.shtml NCEP/GEFS (14 day forecast): http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/NCPE_phase_21m_full.gif http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/ncpe.shtml JMA (9 day forecast): http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/JMAN_phase_51m_full.gif http://www.cpc.ncep.noaa.gov/products/precip/CWlink/MJO/CLIVAR/jman.shtml Please note that last Winter I reported on Kyle MacRitchie’s specialist MJO predictions which seemed to always differ somewhat from the big 4. I have been in contact with Kyle during the summer and he feels that his charts are not adjusted frequently enough and should not be compared to the others. So, unless Kyle improves his updating standards, I shall discontinue reporting on his predictions for the time being (given the current uncertainties I may have a closer look again shortly and report back later or in next week’s report). COMMENT: A rather mixed picture yet again but slightly more encouraging signs with all 4 models bringing the MJO to life again. The UKMO with it's shorter forecasting period moves through the COD and points towards a later emergence into phase 8 or 1. The ECM just breaks into phase 1 with a few ensemble members suggesting slightly increased amplitude. The GEFS goes more strongly into phase 1 but almost overshoots into phase 2. The JMA currently shows the best outcome moving more directly into phase 8, close to the phase 1 boundary at good amplitude. We need this general trend to continue and for stronger amplification in the important phase 7, 8 and 1 to help assist with some greater HLB. This is definitely one to watch. These charts will probably automatically update daily around 1600 (if not, then please use the link which I also provide). Northern Hemisphere Snow Cover: I show animations for snow cover and sea ice changes. These are produced by the National Ocean and Atmospheric Administration (NOAA). When you go to their site you can change the date range and go back over 10 years. You can change the speed and pause on any particular day. These are brilliant, very informative charts and great to play around with. I’ve have re-set the links below to show the last 2 weeks from December 26th to January 8th but you can change these again: a) Animated Northern Hemisphere Snow Cover Changes (updated by NOAA January 9th): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/nh/20161226-20170108 I’m not sure if this will work but I have tried to freeze the most recent chart. http://www.natice.noaa.gov/pub/ims/ims_v3/ims_gif/ARCHIVE/NHem/2017/ims2017008.gif b) Animated Europe and Asia Day Snow Cover (updated by NOAA January 9th): https://www.ncdc.noaa.gov/snow-and-ice/snow-cover/ea/20161226-20170108 As above, I hope this shows the most recent chart http://www.natice.noaa.gov/pub/ims/ims_v3/ims_gif/ARCHIVE/EuAsia/2017/ims2017008_asiaeurope.gi BRIEF COMMENT: Just look at the rapid build-up of European snow cover during the last few days and the renewed rapid growth in the Arctic sea ice extent. There continues to be well above average snow cover over northern Asia and this has continued to expand southwards and south-westwards. Scandinavia is once again fully snow covered, including the south (the high central plateaus usually have pretty complete snow cover for most of an average Winter). Current Arctic Regional Surface Temperatures: GFS – Northern Hemisphere Current Temperatures for January 9rd 1900 (12z – 1300 T+6): http://modeles.meteociel.fr/modeles/gfs/run/gfsnh-9-6.png?12 and here’s the link to live charts if you wish to view future changes (updated 4 times a day): http://www.meteociel.fr/modeles/gfse_cartes.php?&ech=6&mode=9&carte=1 North Pole: -24c to -28c (little change). Barents Sea/High Arctic: -4c to -24c (-4c to -12c). Scandinavia: south -4c to -8c (-4c to -12c; north -12c to -16c (-20c to -24c). Northern Siberia: -28c to -40c and below (-32c to -40c and below). North West Russia: -20c to -32c (-24c to -32c) North-east Europe: -8c to -20c (-4c to -12c). Greenland: -20c to -40c and below (-16c to -40c) Canadian Arctic: mostly -12c to -40c (mostly -12c to -28c). Alaska: -8c to -20c (-4c to -12c). Please note: For land masses I have tried to focus on readings away from the coasts and away from any mountainous areas. You can follow the trends by looking at the latest data at any time from now on. It is vital to note the time of day to take account of daytime/night time variations. So for like for like comparisons, for example the 1900 charts for each day should be available to view from the 12z (T+6) updates which are published around 1600 to 1700 or about 4 to 5 hours later. Svalbard Daily “Maximum” Temperature Forecast for 10 Days: Here are the links to the 3 Svalbard stations that I am monitoring. Central/West Svalbard – Longyearbyen 28 m asl: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/forecast.pdf January 10th -12c; January 14th -9c; January 18th -6c. North-West Svalbard – Ny-Alesund: http://www.yr.no/place/Norway/Svalbard/Ny-Ålesund/forecast.pdf January 10th -12c; January 14th -12c; January 18th -8c. Central South Svalbard – Sveagruva: http://www.yr.no/place/Norway/Svalbard/Sveagruva/forecast.pdf January 10th -19c; January 14th -16c; January 18th -11c. Please note that the links above will update automatically at frequent intervals throughout the day. They are the Norway met office’s predictions. We need to be aware that these are only a forecast that is subject to change and I am told that the Arctic surface temperature forecasts are not completely reliable even at quite short range. BRIEF COMMENT: Special Note: These Arctic surface temperatures are at their lowest at the ideal time around Wednesday, January 11th to Saturday, January 15th just when we will be locking into to that Arctic airstream. A real bit of good luck for a change! So, I’ve done my bit, who’s going to get those 850s below -8c across the whole country on Thursday and Friday. This may give us a slightly higher chance of snow rather than rain or sleet in lowland areas further south given any favourable but marginal synoptics. To put the above figures into context, here is a link to the main Longyearbyen site: http://www.yr.no/place/Norway/Svalbard/Longyearbyen/statistics.html This shows monthly means and actual highest/lowest temperatures recorded during this winter and goes back further. Svalbard has been seeing “maximum” temperatures often running at 8c to 10c above their long term average throughout most of 2016. This has been the pattern for several years and is reflective of the warming Arctic and record low sea ice cover. The very recent trend has been slightly more encouraging with temperatures falling to slightly below their long term averages for 4 days in early December which is the longest period of below average temperatures for about 3 years! Then maximum temperatures rose to around zero over Christmas and have trended somewhat lower again since then. Final Comment: What more can I add. Uncertainty – yes; a very exciting period for model watching – yes; is there cold and snow around – yes; will we have a prolonged cold spell – who knows! Next Update: Part 2 of this report with Judah Cohen’s latest update should be posted around 2330 this evening. My next weekly report should be on Monday evening, January 16th.
  38. 69 points
    Netweather will be gathering a choir made from members to sing the forums version of 12 days of Christmas. (in this case 7 days) On the first day of Christmas my true love said to me: A cold long fetch Easterly On the second day of Christmas my true love said to me: Two undercuts and a cold long fetch Easterly On the third day of Christmas my true love said to me: Three channel lows Two undercuts and a cold long fetch Easterly On the fourth day of Christmas my true love said to me: Four whiteouts Three channel lows Two undercuts and a cold long fetch Easterly On the fifth day of Christmas my true love said to me: Five snow ploughs Four whiteouts Three channel lows Two undercuts and a cold long fetch Easterly On the sixth day of Christmas my true love said to me: Six wild goose chases Five snow ploughs Four whiteouts Three channel lows Two undercuts and a cold long fetch Easterly On the seventh day of Christmas my true love said to me: Seven swans a skating Six wild goose chases Five snow ploughs Four whiteouts Three channel lows Two undercuts and a cold long fetch Easterly
  39. 69 points
    The final whites of the eyes of the resurgent vortex are now fully in focus of NWP modelling, ahead of eventual programmed momentum transport from Greenland to Siberia after this inauspicious end period of January to start of February timeframe. Indian Ocean tropical signal is creating another 'noise response', such as it did in December ,over the well fused together ocean/atmosphere Nino base state. The reduced tendency in atmospheric angular momentum from the heady values of recently is temporarily scrubbing some of the massive surfeit of westerly wind anomalies across the Pacific and creating a very pseudo and transient Nina-like synoptic response. Despite total budget AAM remaining high Only a very minor subtle shift of jet energy northwards across the US, but magnified greater by the interim strong vortex across Greenland to provide the very uninspiring flat westerly pattern downstream across the Atlantic of the next 10 days or so. As amplification starts to occur upstream in the Pacific, the net longwave tendency downstream is to retract the heights to our south and over Europe westwards into the Atlantic, and, with recent negative tendency in frictional torques as a manifestation of suppression of relative AAM tendency, this has the effect of beefing up the Azores High. This process is now well advertised in the 8 to 10 day modelling period. Frictional torques have now bottomed out, and starting to trend up in recognition of the continuing low frequency Nino signal in the Pacific. This sets the floor limit for relative angular momentum before rising once again At the same time, the MJO is set to continue its eastwards movement through the Maritimes and then onwards to the Pacific during the course of the first half of February . We should be mindful that modelling of this activity beyond a few days will be unreliable, and likely in that respect that progress will be underestimated. This is especially as MJO related activity is usually increasingly active approaching the later winter and then early Spring periods. With displacement and considerable perturbment likely of the stratospheric vortex during the very first part of February, and another round of soaring angular momentum as the MJO arrives at Phases 5 and 6, with the tropical signal increasingly gaining amplitude, then increasing eastward and northward progress of poleward rossby wave activity arrives in the Atlantic as the signal engages the Pacific as it did during this month and associated cold spell. Nino Region 1.2 (eastern region) continues to cool and assist the evolvement of a traditional later winter Nino cold pattern. With the vortex paying a price for its unwelcome re-staged party gate-crash of our winter, the scene is set for an increasingly amplified Atlantic profile leading to greater and greater blocking potential particularly later in the month. Both the long-wave pattern and Nino forcing look much better accorded to stronger and more defined heights over the NE Atlantic, southern Greenland and Iceland as the month progresses. Better than those seen this month, and with a stronger and more east based NAO profile It looks good for steadily increasing polar vectors through NW, N and NE through the progress of the month - beginning with polar maritime incursions in the earliest part of the month and becoming progressively colder from there
  40. 69 points
    Very appealing GEM Ensemble and GEFS tonight, illuminating a strong coherence to the mean over Greenland just sniffing Iceland in the extended range (especially the GEM). I would rate the GEM of most value here, as I think it has a particularly good handle on the Arctic basin.
  41. 68 points
    We shall see how it unfolds. ECMWF Monthly also raises +ve MSLP/GPH anomaly to NW (S of Greenland) into week 2; interestingly it supports GloSea5 on broad idea of a colder than average spell much/most of Jan, with varying NW/N/NE flow (perhaps E'ly later in month); even by week 4 with unusually prominent -ve temp anomalies for southern UK (given the lead time). One way or another, model output looks an awful lot more interesting versus this time a week ago.
  42. 68 points
    Indeed. It'll be interesting seeing how ECMWF Seasonal output tomorrow (and for that matter, EC Monthly this evening) handle prospects as we crossover into December, versus CFS (albeit that product doesn't receive the same weighting in UKMO seasonal assessment as GloSea, ECMWF and MeteoFrance-Climate) and what sort of parallel exists with them all, or not. GloSea continues it's path to resurrect the blocked theme later November and on through December... whilst the signal for an extraordinarily weak stratospheric PV remains an underpinning and noteworthy theme. Given how well the model has synthesised developments 'up aloft' since September, it does lean to fair confidence in how this now unfolds, at least in the broadest sense. 2nd half of winter could well be in a different 'mode' to the 1st, but let's see how Part 1 gets on.
  43. 68 points
    Reasons to be cheerful: Lagged significant tropical convective signal from tropics on course to sub tropics to kill +NAO regime Cooling underway of Nino 1.2 (eastern) region, whilst further imminent WWB to sustain warmth in Central Nino regions. MJO return to Indian Ocean later this month should underpin this trend of cooling of eastern region, and help the process along of 're-shaping' the forcing from the Pacific towards a centrally controlled one which teleconnects to adjustment of Nino H500 pattern of heights south of Greenland (destination ultimately perhaps Iceland into February) The latest Kelvin wave activity assures yet further westerly wind additions to the atmosphere supplied from the Pacific to sustain +AAM WAA bombardment on the polar vortex. Large implications follow on from next MJO cycle as it potentially moves back towards the Western Pacific through February. Especially as the matured Nino evolves favourably in terms of forcing a cold later winter pattern. Yet more poleward rossby wave bombardment - with the AO already well established and tanked -ve The long wave pattern suggests that an evolving -NAO moves from west based, initially, to a more central/eastern the closer we get to February. With the vortex displaced away to our NE and a -AO/-NAO pattern being carved out, there is only one way for the jet stream to ultimately head. Underneath us. Putting all the factors outlined together,and on the basis we have achieved a -AO flip already, with the polar field carved across from one side to the other, and time suggested to be borrowed for the first half of winter +NAO regime - it appears counter-intuitive and hard to envisage as we head into the second half of winter (and increasingly then towards the last third of winter) how we return sustainably to a south westerly regime post Atlantic amplification. Something has to surely give sooner or later. I would continue to think that even if somehow the upcoming phase of change towards a colder pattern we see, at last, this winter, manages to contrive an 'almost but not quite there' scenario' - with heights evolving to our NW (and then perhaps N as we get into Feb) Ultimate arrival looks something like the models are trying to concoct right now and resembles attempts towards something along the lines of 1983. Its a case of whether we get here sooner than this sort of timeline or round about the same time. There remain decent chances we could get there sooner. The upcoming amplification maybe just an Hors-d'oeuvre rehearsal
  44. 67 points
    Evening All. 'Positive bias' Thats the phrases of the day - once again it fully represents the GFS OP & ENS suite... Im sure ( well hope ) without repeating the whole of Saturdays post that most people have now grasped the concept of how difficult it is for models to balance energy distribution between the Northern & Southern Streams, more especially the GFS that certainly under resolves that southern arm. Having taken a scooting glance at the 00zeds & now the refreshing 12's we have seen the same reoccuring theme from the models as we did Mon through Late Tues where in the mod term forecasts ( 144-192 ) The GFS ops + GEM drive significantly more energy into the Northern streams before slowly retracting the energy southwards in subsequent runs- I would say thats a 'Positive bias' The other extreme of the spectrum - but equally taking the background signals into consideration-& probably the higher probabilities of occuring are the UKMO & NAVGEM - these could ( unproven ) have a slight negative bias where in these split jet scenarios they slightly overload the southern arm creating the favourable retrograde pattern & undercut- ECM 12z - SLAP BANG IN THE MIDDLE. So as a forecaster you have to go on past experience, & like the perpetual GFS failings of previous years & even identical failings thus far this week you have to conclude that every ensemble thats more positively tilited at 120 that the ECM can for now enter the file marked 'trash' - probability of verification 20/80... We then head over to the 'cluster' of ECM / JMA with their neutral feel & the NAVGEM/UKMO blend that sees the most favourable positioning of the 4 key features on the map at 120 - so lets examine those & see where the changes will occur over the next 48 hours. UKMO 120 * High pressure in the atlantic sees a slightly negatively tilted high in the furthest position NW compared with the rest of the suite - drawing a slight continental flow * Atlantic low because of the negative tilt is being forced NNW up towards Greenland * Iberian low - being supported by a high %age of the available energy in the jet which is in the southern arm- The key here is the more you get in the southern arm the further the East/North East propergation * Scandi Shortwave - Crucial in its location as its our trigger low- & its being forced south because the northern arm is weaker & its looping like a 'n' shape with a sharp inflection point. ^^^ all the above features are in the right place ( for cold ) all because the energy thats going south is enough to get them into favourable positions- it wont be 100% of the full energy as there be a northern arm otherwise we would have a full retrograde up to greenland... For reference the GFS - * No iberian Low * Scandi shortwave no recurve - its being projected east because the northern arm is flat with fast energy POSITIVE BIAS...... So the expectation here 80/20 is the landing zone cone if you like is somewhere between ECM & UKMO - Based on history ive observed - UKMO a good performer in undercut scenarios ( rem Mar 13 ) - Scandi Shortwaves are near 100% of the time projected to far east & sharpen up as you traverse the timeline of a model so @168 it may be all the way far east as Germany only by 120 its back in Holland & 72 / 96 it can come back as far as NE france ( Rem 2009 Easterly ) Therefor my forecast for the next 24-48 hours is for 0-72 minimal change 72-120 GFS to move to more negative tilted low in the atlantic & to show signs of developing the Iberian Low-Also ensemble suites pick the same signal up - perhaps tomorrow PM ( as this is todays 96-144 charts > tomorrows 72-120 ) 144 onwards a high probability of the mild / flame ensembles evaporating ( for the second time this week ) to be replaced by an easterly flow of varying degrees of coldness - ranging from 0c - to maybe -8c We will have to see whats the best possible cold flow we could tap although UKMO 144 looks almost best case out of a mediocre retrograde... Moving past that - the hemisheric profile looks to get smashed by that huge pacific ridge - importantly the vortex needs to stay in the European or Eurasion quadrent- we DONT want it dropping west across into canada as that will stop any vortex split & cross polar ridge ! All in all we are creeping to a good solution- that will be cold--- can we make it to 'snow' cold... December CET sub 4c projected.... S
  45. 67 points
    The -ve screen temp anomalies from last week of Feb all the way on past mid-March (one such frame below) are generally weak - but versus previous output, now quite striking in latest EC Monthly, especially re longevity. Meanwhile, +ve PPN anomalies shift increasingly southwards through England and into continental Europe, with mean flow varying N to NNW to NNE throughout most of run, before losing any significant signal against climatology later next month. This fits well with UKMO suspicion re colder start to spring. Something afoot....
  46. 67 points
    so then, to sum up the model outputs over the past 24 hours for the coming days it might snow, it might not, it might turn cold, then mild, then cold....or it start cold, get colder, and then turn mild, or maybe it will start mild, turn cold, turn mild, and then turn colder.......................and I almost forgot, it might be dry, but it might be wet, or it might turn dry only to get wetter later........I don't know about anybody else, but I'm so confused that I don't know what my name is or where I come from! (FI is at T72 for me!)
  47. 67 points
    Hugely interesting 2-4 week period upcoming. The MJO cruising through the Pacific has triggered a pattern change to a notable -AO and more neutral NAO, although in reality the NAO is more positive still due to a residual trough signal in the North-east Atlantic. Fundamentally the game has changed as angular momentum has been moved upwards and the consolidation of the MJO in the next week is going to take it to the heady heights of +3SD. For an angular momentum junkie like me, these are rarified times and emphasises the lofty company we're keeping - only 1997/8 and 1982/3 witnessed such high levels of global westerly wind balance. GEFS product below is off the scale ! This poses a really good opportunity to get stuck into the likely upcoming broad scale hemispheric patterns. The surge in westerly winds over the tropics is forecast to peak around the 6th January. That makes sense with MJO where it is now and likely to be in the next week, allied to sub-seasonal low frequency forcing related to El Nino. It will take around 21 days for these anomalous westerly winds to be fluxed poleward. Note the previous trend for fluxing of positive (westerly) and negative (easterly) wind anomalies over time. That sets up a date around the 27th January where we would normally expect the NAO to fully respond to this forcing and flip properly negative. The EC EPS is rather more keen than the GEFS /GFS in dislodging a part of the blocking high over the Kara Sea (favouring more of an Alaskan ridge). This subtle development opens the door for pressure to fall in the Western Pacific as the high drifts south and east. This also appears to coincide with a Kelvin Wave (yes, I'm using that term correctly) passing through the region. Net result should be for a further addition of westerly winds and spike in tendency in relative angular momentum around the 9th / 10th January. This should induce further hemispheric amplification as the Asian jet is extended and retracted. Allowing 10 days from this point, suggest a northerly type evolution (but still emphasis on cyclonic) is likely between 15th and 20th January. Outside chance of heights rising to our NE from this, but would favour the northerly route. Thereafter It gets really interesting. With an element of tropical forcing returning to the Indian Ocean (and possibly returning to the Western Pacific thereafter), the global angular momentum budget will have reached a high water mark and the only place for tendency in relative angular momentum to go is down, but still within a high overall angular momentum base state. That coincides with the expected lagged impact of the momentum fluxes from the tropical wave in the next week. The GWO framework is extremely useful here as it gives an indication of probabilities of each relative phase when taking account of high angular momentum. Given high angular momentum above +2SD, the only relevant phases here are phases 5, 6 and 7. The initial surge in angular momentum will drive the GWO into high amplitude strongly favouring phases 5 and 6 during the next 2 weeks. Composites favour a Greenland high but that should be adjusted a little to reflect existing and near time conditions, with the emphasis on phase 6 suggesting a continuation of the cyclonic pattern across NW Europe, including Scandinavia. Not overly cold, particularly with the residual+NAO imprint to the pattern, but between 15th and 20th, expect a cooling down. From the 20th we should see a shift in the emphasis of the GWO more towards phase 7 (and not phase 8 as this would require much more significant removal of westerlies which is unlikely given the high benchmark we are operating at). Phase 7 composite for January suggests a west based -NAO, although I've included the composite for February as this will be towards month's end. Stress again, don't be too literal with the interpretation with these composites and the probability of the AO and NAO being more negative at this time should be factored into the composite. This suggests a definite trend to colder conditions towards month's end with the likely key parts for us in NW Europe being a more defined European trough and anomalous ridges centred across the North-east Atlantic. The trough signal across the SE and E USA does imply blocking more towards Greenland. mjo forecast.bmp
  48. 65 points
    To skimp on the frame-by-frame detail and varied complexities anticipated into early Dec, tonight's EC Monthly ultimately heads in much the same direction as it's predecessor, with +ve GPH anomalies to north and +ve MSLP anomaly to our NW (Iceland) by mid-Dec (run ends 18th). Steady as she goes... etc.
  49. 64 points
    Another eps going for a progressive undercut and block development to the north in the extended range, sustained cold from day 8. Very cold European outlook. Pandora's box about to be opened.. just need to nail the drag back of the core of the pv across the sw USA.
  50. 64 points
    Worth noting that UKMO prognosis for January has shifted now. They suspect PNA may be influential; GloSea5 has moved over weekend to suggest anticyclonic/blocked regime will dominate throughout Jan, with milder interludes only occasionally and temperatures generally lower than average. Although severe cold is still considered unlikely, they note that currently around 25% of yesterday's EC EPS members and several GloSea5 members allow reorientation of the block (principally expected to the W) to shift such as to bring a Pc flow. GloSea5 keeps the broadly +ve MSLP anomalies all the way to the end of January, maintaining a colder theme compared to climatology. Deja vu, or on the money this month? We watch with interest... but gloves & scarves ready from next weekend (at least that initial bit of the story comes with high confidence, albeit cold front timing has wide error margin of 12-24hrs).
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