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  1. 112 likes
    So a rather long post ( Will also clip into the winter forecast thread ) However just an update on saturdays post, a large debate around models - & I took the day 6 UKMO & GFS charts to compare for verification- These were both of the 6 dayers GFS on the left. Note GFS flat with no heights in Greenland, UKMO more amplified with heights - Also a circular vortex North of Scandi. UKMO has energy seperation & a closed low - GFS just sends a 'block' of energy through - Look at todays UKMO 72- Comments: -Circular vortex just North of Scandi -Closed low traversing East towards Iceland - Residual heights over Southern Greenland - Arctic High 1040MB. Conclusion UKMO is a clear resounding winner here- every element that differentiated from the GFS is still apparent in the T72 chart, this is a big thumbs up for the UKMO, proof ( on this occasion ) that the GFS clearly has an eastward bias & why looking at developing heights over the pole ( NB UKMO 144 today ) The UKMO resolves energy better... So, onto the SSW it seems an eternity since the first warming started showing up way back in December - but now we are day +6 since the wind reversal- Much of the discussion has been about the 'slow' response in terms of downwelling in terms of creating a significant AO - This is depicted nicely on the NAM index which I have saved from the other week- The GFS bias initially showed minimal downwelling, however gradually ( like the comparison with the UKMO above ) has slowly come into line with a more 'propergating' feature. I think we have been unlucky with the QTR - sadly the NOAA composites page isnt available, however twice there has been significant mid lattitude blocking developing in the locale forecast as a QTR relating to the strat split- However the blocking has been just to far East for us to really gain any benefit - *but* as far as Europe as a whole is concerned in terms of snow this winter could challenge the record books in terms of sustained depth from mid Jan onwards- My memory ( from the old teletext days ) was that St Anton could reach 600CM on the tops by the end of Winter- By the end of this week it will be North of 400CM Also records going in Greece with snow in Athens & -23c reported North of the region- So whilst the QTR missed us that release of deep cold didnt miss everyone... The next stage of this SSW / Split will be crucial for winter as the norm here would be a gentle recovery from the PV ( not to normal strength ) - however if like me you were hoping for something that lasts longer than a few days - IE 1 MONTH then a secondary warming & further splits would be the upper cut to the PV that would knock it out for the rest of the Winter. However just before commenting on that lets see the progression of the downwelling- The charts at the top are from around NYear- now look at the NAM index from the GFS today ( remember its still not the best model for coupling the Strat > Trop ) Here is the NY 100HPA profile V todays Lots more clustering below 5M/S- some below zero. This is why we are seeing the GEFS respond post 192 - Note the AO Ensembles - Starting to gain momentum towards -4. Moving through day 9 on the ECM strat from yesterday we see that the Uwind is still negative but importantly the allignment of the vortex lobes are significantly different to this week - encouraging blocking- Red is the left lobe allignment Blue is the right lobe allignment Yellow is the blocking potential- Its quite apparent that despite a split the current shape of the lobes means that the U wind off the states doesnt support blocking, but day 9 ( alligned to the trop response ) allows for a different pattern that is complimentary towards the jet being sheared up the western side of Greenland & also residual flow alligned SE in the atlantic - We should also see the vortex 'throwing' Scandi Deep cold SW across Europe - This is the jet flow -( yellow ) & associated areas of deep cold. This is a solid -AO / + PNA / -NAO pattern. This is why the models have suddenly flipped to that sharp NW > SE allignment If you are looking for sustained cold then a SSW split + follow up warmings & continual negative zonal winds are the hallmarks of LONG cold spells, * with the usual caveat that we are the SW point of the cold & could always see some milder air pushing back west * This could be a crippling final quarter of Winter for Europe & the Balkans- Best S
  2. 90 likes
    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
  3. 89 likes
    C'mon guys lets give @Paul and the mods a break with the bickering and personal digs type of posts after all it is a WEATHER forum and this thread is for WEATHER MODEL discussion I can only imagine how hard it is for newbies to try and decipher what is going on among all those types of posts so if anybody has any issues with posts / members perhaps it would be better to use the report post button / ignore member button or try and settle it like adults through PM's and also remember the couple of banter threads that exist Now onto the models I will refer back to my post from 8th Jan some statements / thoughts that I made in the post on 8th Jan "I still believe that any low pressures that do develop will begin to take an ever increasing NW - SE track (with the majority perhaps struggling to get much past the UK) resulting in some northerlies / North westerlies bringing the first hints at something cooler / colder to the UK " "My key period for this would be 17th Jan - 21st Jan " starting on this point, I am fairly happy with this still as we move towards those dates as it looks like around the 17th will be the first (of what I think could be quite a few within the next few weeks) at a sliding low attempt dont take the position / strength of the low too seriously as this is still changing from run to run but the NW > SE movement is there and a run showing possible north westerly / northerly / north easterly air by around the 21st onward for a few days onto my next statement / thought from 8th Jan "So what could happen after that?" "Well IMO it looks like being the last week of Jan from around 24th Jan - 31st Jan that the possibility of some fun and games with blocking and colder charts will reach its maximum potential so far this winter." Again I remain pretty confident with this, why? IMO there is still a signal for the last week of Jan for blocking to start to develop / take hold there are some more ensembles showing this but I think this demonstrates my point clearly enough AO still set to nosedive first hints that the NAO might head the same way And with the MJO looking like possibly heading back toward / through phase 6 / 7 by then that could also help aid blocking (again I am only going off my limited knowledge on the MJO and also might need to factor in some lag time) (some of the other MJO forecasts look a bit more uncertain / slower to go toward those phases ATM) Also still worth factoring in effects from the strat warming event(s) that have took place during late December / Early Jan. some more thoughts / statements that I made on 8th Jan "A word of warning / potential spoiler would be a west based - NAO which remains a possibility http://theweathercentre.blogspot.com/2012/10/east-based-v-west-based-negative-nao.html Key Points keep an eye on these beginning to nosedive once the blocking gets nearer https://www.cpc.ncep.noaa.gov/products/precip/CWlink/daily_ao_index/ao.shtml https://www.cpc.ncep.noaa.gov/products/precip/CWlink/pna/nao.shtml be wary of the west based -NAO" All of the above are still true / possible IMO but with regards to the west based - NAO perhaps the chances of this wont be know until nearer the last week of Jan and where the models are seeing the potential blocking setting up / developing keep an eye on the ensembles for more and more BOOM type charts appearing in the run up to the last week of Jan I think the first area to focus on ATM would be the potential for slider lows and the possible snowy conditions that they may bring but I still believe the amount of BOOM charts will be on the rise the nearer we get to the last week of Jan. A few extra points I would like to make 1. I wouldn't worry too much about differences in each GEFS suite on the graphs (rises in 850 hPa temps) as slight changes in positions of possible slider lows and later on blocking highs can shift those 850's heavily in one direction or the other and I think we are seeing the usual ebb / flow of the models trying to grasp exactly where each low / high is likely to set up (possibly whilst trying to factor in ongoing effects from start event(s) and MJO etc) 2. How quickly have we seen in the past that things can change and head down a colder / much colder route a la Nov / Dec 2010 & Feb / March 2018 etc (yes there have also been occasions where charts such as "that ECM" where the cold looked like it was on route to the UK and suddenly diverted but I much prefer to look at things with a glass half full rather than immediately thinking that we have no hope / chance of the cold / snow reaching our shores / back gardens) using the 2 years mentioned above as examples and again I am not saying that anything of that severity is heading our way I am just highlighting how much can change within the space of a few weeks (using today's date 14th Jan and 2 weeks from now would have us in the last week of Jan , 28th Jan) taking the 25th November as the end date as that was when the colder air was spreading right across the UK then 2 weeks before was the 11th November 11th November 2010 > 2 weeks later 25th November 2010 11th November 2010 25th November 2010 an example of how quickly things can change / blocking can develop February 2018 - again I will use the 26th February as the end point as this was when the colder air was spreading across the UK so 2 weeks before was the 12th February 2018 > 2 weeks later 26th February 2018 12th February 2018 yes there was some snow around for some but I am highlighting how quickly more blocked conditions can develop 26th February 2018 Keep calm everyone and try and enjoy how the rest of January and beyond plays out, I still think we are in for some fascinating model watching. And I just want to remind people I am certainly no weather expert, I am just having a go at trying to predict where we are heading and seeing how close or far away I am (and if I am miles off the mark I will own up and try and examine the charts to see what happened and how we ended up with scenario A or scenario B etc) ensembles GEM 0z ensembles FNMOC/NOGAPS 0z
  4. 75 likes
    You know what - I havent seen 1 hopecast on here. People have put all their points of view across in a pretty good mannor- infact its been pretty good debate. The only post that sticks out a mile as pointless is the one im quoting...
  5. 70 likes
    Dear wife, Due to the netweather code of conduct I am unable to tell you this directly now as, otherwise, this will go pear shaped and as we haven’t seen lying snow for 5 years... I can’t risk that. If today’s icon/gfs 00z (17/02/18) charts verified, we could be in for the snowiest spells of weather we have seen in our 40 years living in the south and this could pretty much be a nationwide event. I know that you hate and loathe cold, snowy weather but all I can say is........ get to Tesco’s and stock up on supplies, alcohol and logs as we’re in for the long haul!!! All things going well, I will show you this message on Tuesday/Wednesday as I may be allowed then!!! Amazing charts today, not sure the ecm 12z from yesterday could be beaten but it may have been by icon/gfs 00z runs. Great to see the ukmo onboard, need the ecm back on board later today. Enjoy the ride! Clem (suffering in silence!)
  6. 69 likes
    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
  7. 68 likes
    Leaked express headline for tomorrow. #sorrynotsorry
  8. 66 likes
    Afternoon All I guess a few of you/us are wondering whats going on with the weather this weekend & into next week... Strange, almost 'texbook' cold charts appearing in the models & actually landing with some degree of accuracy.... Well like many - you are probably wondering if its a precursor to the rest of the winter or a lucky double 6 roll in November.... Based on the information at hand I would say the nina base state forecasts of mild westerlies into december & throughout are going to be wrong & on very shaky ground - Looking at the current picture & the run up to the start of the winter season I commented on TWO about NW winters getting more extreme - The NOAA data for AO & NAO show the modes of these metrics becoming more & more diverse & when in a particular phase ( whether that be pos or Neg ) so the metrics would be topping / bottoming out at at close on record breaking levels - The whole post was in reference to the M.winter theory from IBrown To underpin this ( but without the data ) in the last 15 years we have smashed the AO record at both ends so many times - months like Dec 10 / Mar 13 spring to mind- but also the extreme mild ones as well ! However also in the post was the fact that steadily the incidence of Negative months had reduced in favour of more positive ones- so with Heinsite the M.Winter theory carries some weight but poorly communicated without all the facts- What also has become Crystal clear is the fact that the M.Winter or whatever you want to call it could be under attack by more front loaded cold winters especially when the total atmosphere favours a negative state of AO/NAO with winter 17/18 being just that- Post M.Winter ....? The fallout from the polar ice melting is creating massive impacts on the way the jet behaves in November in particular - The fuel needed to ignite the jet is simply missing in action - probably due to the self perpetuating feedback loop that develops at the same time as when the jet & vortex should be positioning over the pole ( Early Nov ) The chart below shows the current surface temp anomaly for November up until 22nd The green scaling is about 7-8c the orange & red 10-15c vice versa blue about negative 5-10 If you look close at the map the dividing line is generally alligned to 60N where the jet is usually located. We have a reducing in measured gradient by around 15-20 degrees > this essentially acts as a neutraliser on the jet- for which we are now feeling the benefits. This troposheric lead feedback is a far larger beast than El nino or La Nina - it covers the entire space North of 65N & a large part of Russia - It certainly needs a name so I am calling it this - Calido el hielo !! What we have is a troposheric feedback loop that feels lime it can run disconnected to the strat until the anomaly becomes muted but the inevitable increasing gradient as we had further into December & the strat can work its way down... So a watch out for future Novembers that Calido el Hielo may be creating more blocked extreme ( warm or cold ) Novembers.... Moving back to the hear & now we are in a rare situation, one of only 6 occasions since 1979 in winter ! of these 6 the EQBO years being just 2. 1st Jan 85 ( Front loaded EQBO ) 20 Feb 01 - So whats infront of then ? A troposheric induced stratospheric splitting event - the net being a massive deceleration of the zonal wind lagged about 10-15 days later. I would go with our splitting event to be dated 29th NOVEMBER !!!! ( This is why I kept referring to 31st Dec 84 in the model thread ) Here was the Jan 85 & feb 01 charts & the associated stratospheric response ( lag back down ~ 10-15 days ) Then importantly the following months anomaly After +10days lag * The key notes here are that the troposhere is primed for polar blocking with a core towards Greenland- Also low euro & Azores heights present... Now, Taking our event to be 29th of November we should see an immediate stratospheric collapse of the zonal wind & from about the 4th-5th & The blocking anomalies to be present from anywhere around the 8th onwards- Lets look at this mornings outputs - these are GFS based & depict a total collapse of the zonal wind - with this depiction being the daddy - showing a -35 M/S hit on the zonal wind which is a reversal at 10MB .... Jan 85 Merra data shows a reversal down to -15M/S Feb 01 shows bottoming out -3M/S So this is why the GFS / ECM are spewing out all this blocked data for first / Second week of December- Based on the science of the lagged troposperic response the 6-12th Dec will be peak for blocking & subsequent cold UK potential with Greenland being the favoured location a Below ave December / Front loaded winter is odds on favourite for me with a high probability of some very special charts appearing! fingers crossed.... Best S
  9. 65 likes
    I came back on here tonight hoping to see some positivity. (I shouldn't really, I've been here long enough to know how it works), yet we are in the midst of a December SSW, a very rare beast. It could and should, give us the winter we've been waiting for, for years. It might not... however, we are in the best position we've been in for years. The models are struggling with an outcome and it's a fact that an SSW will play havoc with numerical weather prediction. We (My family) are losing our home on the 7th January. We will be ok somehow. One of our Netweather members has just been given the all clear from cancer. Is it really worth any animosity over the weather? Something which is out of our control? It's Christmas eve tomorrow, real winter weather is coming (allegedly at some point...) Just enjoy the hunt for cold and have a merry Christmas....
  10. 62 likes
    The problem is, we have many spending hours on this forum, explaining why things may and may not happen. The pros, the cons with a certain setup. The background signals, from Pacific forcings to Solar to the Enso state.Going to great lengths to point out the mechanisms, the caveats, the opportunities. I understand why some feel, why do I bother? 95% are here to do exactly what the forum title says, 'HUNT FOR COLD'. Whether that is looking for a glimmer of hope in a flat zonal profile with poor background signals or in more interesting times, aka right now, it is the whole point of being here on this forum surely? Clearly this forum would be redundant if we all lived in Antartica, but we don't, we live in an area that is usually beyond the reach of any easterly train from the east and with a continuous warm belt of water being pumped up from the Gulf of Mexico to our west. The odds are stacked against us right from the off. The dice are heavily loaded and they are not in our favour. And that is the thing, the crux, the whole point is the chase itself. I won't go as far as to say the cold actually landing is secondary, but before it does, the chase, the hunt, the hope, the despair, the rollercoaster, that is why we torture ourselves on here every winter. I am a die hard lifelong Spurs fan, so that probably makes me a masochist! But the fact remains that for the 95%, just seeing those cold charts appear gives us the buzz we all crave at the time. That may make me look like a total fruit loop in 'real life' but I know full well most of you know exactly where I am coming from!! It is a shame then that we will always get one or two miserable posters who take a few op charts as gospel and on complete face value. Bad enough but to then, through no skill but their own negativity, extend that op chart out to several weeks / months beyond is what really gets people's backs up on here.
  11. 61 likes
    Reading this thread tonight has been a real rollercoaster....have to wonder why those who believe the weather is nothing but chaos with no discernible pattern bother to spend time on a forum where the main thrust is to try and make sense of complex signals and decipher a path forward - but there you go. Takes all sorts I guess.... ...and on the subject of signal deciphering all still looking pretty good, isn't it? I have a slightly warm and fuzzy feeling at the sight of this EPS chart for the 18th Good to know that GSDM theory has a basis that produces the goods. Signal for isolation of the trough underneath a growing band of high lat blocking is growing, and on schedule. To reinforce the fundamental reasons for this - time to post the MT chart that David has already put out there tonight...just for double emphasis It's a really very impressive spike at 30N - and to summarise David's detailed argument into a brief sentence - it very much increases the chances of our strat warming becoming a major one. This sharp increase in momentum will do all kinds of nasty to the vortex - but it also creates a signal for increased atlantic blocking as eddies downstream of the spiked pacific jet form. NWP has been slow to pick up on this - but that EPS chart suggests we have increased clarity now. From here? EPS at 10 days suggests again that the expected pathway may be accurate. The trough will sink south, and with it will come increasingly cold air and wintriness to high ground. This is the start of our winter proper (at least in my eyes) but don't expect widespread snow at low levels quite yet. However - this period will signal the start of the real cooldown. And from there? Time to return to GSDM forcing because strat reinforcement of the pattern will be a little way off yet. Tendency of AAM will begin its next downward cycle soon. This will signal in effect a reduced momentum signature at 30N and opportunity for enhanced momentum further north. However the difference this time is that our next MJO cycle has kicked off, with moderate wave activity emanating once again from the pacific. This will aid in preventing the pattern from becoming too flat, and I would suggest we will see a reinvigoration of the atlantic as we head into Xmas week (despite the higher than average pressure anomalies out west on that EPS chart) but with the trajectory to the south rather than through the heart of the UK (as is happening this week) as heights to our NW serve to deflect the jet on a NW/SE axis. Shamelessly cherry picking a GFS extended image from the 18z rolling out now this chart for Xmas eve would be about what I would expect though perhaps with a greater maintenance of heights over Scandy Systems tracking beneath the block heading towards mainland Europe. Polar maritime airmass mixing with a trough that is beginning to pull in air from the NE. In essence becoming progressively colder on average. So - when does all this give us snowfall at low levels in the south? Don't know yet - don't want to guess. Depends on how quickly cold air can be absorbed from the NE and just how entrenched the block becomes. But chances certainly exist prior to New Year if the flow is right. If not it wont be long after NY before we see 850s in the right kind of zone with a flow that will be evermore easterly on average. And all this being forecast on 13th December rather than 13th February. Warm and fuzzy all over again....
  12. 61 likes
    One final post before bed. I am going to eat some humble pie and give huge praise to Tamara because I am afterall fair. I have been looking at some previous model runs and posts on this thread for the period 29th Jan. Look at what the GFS was predicting for tomorrow on the 29th Jan. This is what Tamara said on the 29th Jan. "However, the upstream jet, is set to decelerate rapidly as pressure rises over the Pacific and re-build the Aleutian Ridge. In the Atlantic sector, the retrogression of the pattern will tend to angle the Jetstream more NW/SE and, conceivably, enable build of pressure over Scandinavia. With time, as the disrupting trough gets separated from the Canadian lobe of vortex, downstream amplification from the Pacific sector becomes possible at the same time as the wave 2 response is activated by rising pressure over Scandinavia to work on the vortex in tandem with the Aleutian Ridge. It is key at this point that the vortex is sufficiently weakened to allow the bleeding of secondary systems to be cut off from the Canadian lobe - and hence terminate the thermal gradient." https://www.netweather.tv/forum/topic/87058-model-output-discussion-25th-jan-the-final-third-of-winter-beckons/?page=12#comment-3534098 Astonishing forecast and I cannot give her enough praise.
  13. 61 likes
    There are too many people on here trying to stir.. its not fair for newbies and not fair on those posters who spend their time providing us with thoughts and considerations.. this is the model discussion thread not a thread for .."the gfs is better or has this nailed" we are dealing with computers interpreations of data.. the charts you see are not handed down by mother nature and therefore not going to be correct all the time. Seriosuly i would ban most of the posts on here this morning. Wake up enjoy the snow coffee and potential you have and stick to the thread. Im not a mod but i have been a member for many years and ita horrid to see how this thread is tainted sometimes. OSW out.. ( sorry mods but it had to be said)
  14. 58 likes
    So sorry to hear that mate Dont want to clutter up this thread but im sure i speak for everyone in wishing you the very best and hope you will be ok.
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  16. 56 likes
    Ho hum dee dum. Interview done and back to the phone to see the most awesome GFS output of the season. Being blunt - pity it's GFS...but maybe something in the data has changed and we'll see ECM latch onto the same later. I hope brethren in the SW have woken up, because we'd have people drowning in the drifts again....... Usually a run like that would be written off...and in all probability it is overly extreme BUT worth pointing out at this stage that the evolution is not out of kilter with the forcings that are being applied to the north Atlantic circulation. Recent EC strat charts have shown a signal for a block to the W/NW and a jet driven further south, and so a split flow like that is entirely within the envelope of the possible, as impacts of the SSW increase. I'm sorry I can't access all my charts etc on my phone, but once home I'm going to have a really good look at the evolution of the pattern and see what may be what. Meanwhile don't forget that Tuesday is approaching and can still deliver for many. Just needs a westerly tweak as a product of underestimation of high pressure strength....something we have seen several times before. Jan 18 today. Can anyone remember the gloom and frustration of 10-14 days ago? Neither can I. Shows things can move very quickly in weather terms at times, and gloom should always be tempered with optimism when the signals are good.
  17. 56 likes
    What's interesting at the moment is the consistency of the ECM op forecast for Tues/Weds. To be honest it's slightly surprisingly consistent - and the fact that both timing and angle of the slider/incoming trough have remained in the same 12 hour time bracket for the last 3 days makes me wonder whether finally we have a handle on the rate of downwell and strat imprint onto the trop pattern. The diving, sliding low remains on a trajectory that is mostly west of England and steep enough for an undercut of cold air to turn the moisture to snow for many. Confidence in this scenario is now about as high as it can be at 168 hours, and before too long we can begin to look at what may follow. So - why such confidence? Leaving aside the MetO reports/video (which if interpreted say a lot....) and GP's tongue in cheek comment about the comparative EPS / GEFS suites there are a number of reasons to be approaching the kind of confidence in product that was possible for the Beast. Ensembles first - EPS ensembles have been rock solid now for days, and the depth of the trough anomaly over NW France is the strongest low pressure anomaly in the NH for next week. Note too the strength of the high - and the expectation therefore that this trough is going to drop hard and fast down and through the UK. Snow chances increasing by that fact alone. Berlin strat slices are also revealing - at 50hpa we have a very slow westerly average now, and a main vortex lobe to our east that has shunted way over the Siberia at 240h However a residual strat trough lies across Asia and Europe....and heights to the NW are forecast to build as energy transfer across the north atlantic simply dries up. 150hpa image shows the approximate end result, also at 10 days There is less of a straight easterly component to the forcing at this point than we had back in Feb, so no scandy hieghts yet in all probability....but as the arctic high strengthens in response to the downwelling of negative anomalies from the last couple of weeks it looks likely to me that easerlies by month's end and into Feb...and maybe more scandy heights in time. And tropospheric forcings? Calculated GLAAM tendency currently is stalled - but awaiting an anticipated uptick which will produce more of a shove for high lat blocking in the 10-14 day period probably, just at the same time as the strat impacts are peaking MJO has been advertised by others to be re enteritng 6 - 7 - 8 before too long. All of this is just fuel to the stratospheric fire. So - if we are to see a fail where will it come from? Not from a rampant stratospheric vortex. Not from a flat Nina signal in the pacific. Strong trough activity off Canada as very cold air hits warmer seas? It will certainly create some sparks via a steep temperature gradient - but is there enough westerly momentum at present to send this through the blocking signal and flatten everything out (as GFS, with its less good strat model keeps playing around with)? Cant see it. Downwell timing has done for that option. Might even help by putting a bit of sparkle into what is left of the jet as it splits/dives south and feeds the trough over time. Solar uptick as per Dec 2012 when everything went t*ts up? Spaceweather currently reads "Spotless Days: Current Stretch: 8 days" - so not a spot in over a week. It's about as good as it can be. And to finish - a look again at the forecasted 850hpa anomaly out east. This has strengthened considerably - now forecast to sit at -8 to -10 from normal in parts - so once we get more of an easterly feed come month's end it is potentially going to turn extremely cold. Time to look in detail at that scenario later. For now - Tues/Weds is going to be interesting and the more cold air we can get in situ from Thurs/Mon the better things will be. 850 temps for Mon as the trough prepares to dive/slide look pretty good to me as a starter of the spell. It isn't going to be diving into warm air that's for sure. Marginal event - but someone somewhere will cash in. And with luck we all get some of the action soon after.....
  18. 55 likes
    I'm here - been working and have also had to pick myself off the floor after checking the 12Z. Best ever trop response that we have been able to track following a SSW, oh those of little faith lol. I did think of buying all the snow shovels and salt in B&Q yesterday and then selling it back to them next weekend.... I have been convinced of an epic cold spell for a long time now (since before the split but my resolute belief was reinforced when I saw the residual Hudson Bay daughter vortex getting taken down). It may have taken the best part of 10 years but finally we are seeing the makings of an epic spell when you take the strat vortex out of the equation. Even @TEITS may finally have to concede that there is something in this teleconnections Malarkey!
  19. 55 likes
    ...and by 29th, 27 members have us in a chilly cyclonic NW-Wly; 24 in blocked, cold N-NE'ly.
  20. 53 likes
    So I mentioned earlier on about very high angular momentum levels, which would normally be associated with a strongish El Nino. GWO in high amplitude phase 6 orbit, expected to move towards phase 7 as the MJO component moves through the West Indian Ocean this week. There is a persistent +ve momentum signal across the tropics and sub-tropics which is holding up this unusually high angular momentum signal. Not much scope for a drastic drop in inertia although frictional torques are as expected strongly negative. When the MJO signal swings through the East Indian and Maritime Continent, angular momentum tendency will rise, driving a phase 5 projection in the GWO around 10th December. Composite: This doesn't fully capture the blocking signal over the Eastern Arctic, so some manual adjustment on this required, but the key messages - Alaskan trough, +ve height anomalies to the NE. GEFS for that time alongside the composite: Again, don't get hung upon on exact placement, the broad gist is that at that range, reasonable confidence that the GEFS mean is about right. The strong presumption from there would be for a phase 5-6-7-6 type evolution (herein the beauty of a conceptual model): There is some manual adjustment necessary to these to inflate +ve height anomalies to the NE and reduce +ve height anomalies to the west of Greenland, but some westward pull of the man trough over the North Pacific is the key thing here. That allows any blocking to our NE to manifest itself, and would consolidate a monthly expectation for +ve height anomalies across Scandinavia. Either way, a challenge to any view of returning zonality at any point during December.
  21. 52 likes
    The atmosphere is now reflecting a Nino state and has been for a while - and that chart is a change over the last 30 days chart. The actual anomaly charts look like this Still very much Nino and not Nina. What the oceans look like come March is of zero interest in any hunt for cold now, and any moderation in Nino over the next 6 weeks will not make a real impact on this winter's season. This tweet is frankly nothing more than a scare story. His twitter feed is extremely uninspiring and rather basic. Nothing to see here - move along...
  22. 52 likes
    All this fuss about downgrades - 'chill' out ! Looking at two runs 24 hrs apart so examine the same time stamp - from last night's 12z to tonight with a helpful Polar Bear diagram included. As you can see the Polar Bear still on course to arrive, just a slightly less ferocious looking bear this evening..
  23. 51 likes
    I don't think there has really been a signal for snow pre-SSW or immediately after, looking in depth at the drivers, I admire your enthusiasm to put a dampener on the outlook despite the overwhelming pointers from the likely impacts from the eventual SSW downwelliing in concert with lag of MJO moving through colder phases (7-8) plus other drivers such as anomalous East Asian Mountain Tourque and +AAM which will help amplify the flow at high latitudes. It has been stated on here by me and others that there was likely to be a few weeks after the SSW started until the impacts were felt in the trop and also the lag of the MJO now headed into 'colder' phases. I think the main reason why we have been stuck and continue to be stuck in this pattern of waxing and waning mid-latitude block with all the upper flow energy over the top, but increasingly flowing NW to SE into the deep eastern Euro trough is to do with not just a strong Pacific jet extension but also the lag effects of the slow MJO stuck in phases 4 and 5 between mid and end of December, these are ‘warmer’ phases that tend to be hostile to high latitude blocking bringing cold to the UK but favours mid-latitude blocking and cold for E/SE Europe. The reason for the slow MJO propagation down to a few likely factors, that were mentioned a while back, including equatorial Rossby waves moving westward along with –AAM which have interfered with the eastward MJO propagation. Also the wave driving into the stratosphere weakening the SPV has probably constructively interfered with the MJO propagation too. However, the MJO now looks to speed up through 7 and 8 and although GFS and EC take into the circle of death (COD) / or MJO dies off over the Pacific, the phase 8 impact on the patterns should remain once MJO has gone into COD, so shouldn’t be duly concerned with this. The downwelling of easterly winds from the strat to trop still forecast and this will be a big driver after mid-month. 9th Jan 14th Jan So although the charts look crap atm, due to the background signal explained above, we should hopefully see the models pick up on better patterns for sustained cold and snow potential for us in week or so as impacts of SSW, MJO colder phases, +AAM/EAMT work through.
  24. 50 likes
    Well the models are having fun with everyone, up down, roller coaster covers it. But in the quieter world up aloft what has been happening? Obviously it is the 500 mb anomaly charts. They are means so do tend to be less up/down compared to the synoptic 6 or 12 hourly outputs. Indeed I would suggest it might be a better idea to simply look at the synoptic 500 mb chart run to run or better still to compare like runs, you may have heard that somewhere else before! Anyway The ECMWF-GFS this morning Not surprisingly they are not that different to what they have predicted over the past 4 or 5 days, see below Atlantic ridging towards Greenland and EC still with GFS now showing a building of ridging over Scandinavia with an extension west towards Greenland. Something that the occasional run on the 6 hours outputs has suggested. Marked troughing on both remains into Europe. The configuration on these two shows lower contour heights on EC compared to GFS. However on both the upper flow shows the cold will persist over the next 6-10 days. Okay it may wax and wane but no signal showing for any mild air for the UK. So what about NOAA and it has a chart that covers 8-14 days out. The 6-10 last evening, largely between the UK and Scandinavia well north with the flow dropping into the European trough. About a week ago the contour flow had the slightest hint of this. The actual +ve height anomaly is show away from any of this, just off the American coast. With such a meridional flow obviously the contour heights over the UK area are higher than the other two. This has little effect ob surface temperatures, indeed if there is any surface ridging in between weather systems might create lower values at the surface. To me the strong flow out of America does leave a question mark for day to day. Will any deepening systems move NE or SE once into the eastern Atlantic? With the deep trough east of the UK one would expect them to steer SE or ESE, which may provide some excitement if they get close to the UK. Looking at their 8-14 day chart and perhaps the most interesting change from the 6-10 is the increase in –ve heights over NW Europe. Again little signal for any mild air. That is unless we get a flow not easterly but SE/or worse SSE with air originating from the Med. Nothing to be concerned about in the next 6-10 days but a possibility beyond that. So, overall the cold will continue, the synoptic models will come and go so to speak on its depth and ideas on where/when any ppn will occur. Up to 24 hours out forget what the models may predict, they are right a few times at longer time scales but not often. Just think back to summer set ups and how often they get the rainfall correct? In winter there are another 8 or so additional variables to get right. Hope this summary helps calm the nerves a little. http://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html
  25. 50 likes
    yet more output upgrades.....*yawn* change the record, it's boring now....what a boring climate we have, all it seems to want to do is snow all of the time and blow hoolies from the east.....I've heard about this mythical beast called a 'Pest from the West' influenced by a body of water called the 'Atlantic' (no, I've never heard of it either)....Perhaps one day we'll get out of this boring rut of incoming weather and get to see one of these mythical beasts again?
  26. 50 likes
    If I may clarify a point here. I have absolutely no idea who are members of the so called "mildness" gang but I am certainly not one of them. It is no secret that I detest cold weather and I do so mainly for two reasons. Firstly, the imprint of 62-63 will forever remain with me and secondly, and far more importantly, as a vulnerable, elderly pensioner, and of course I'm not alone here, cold weather very much affects my health. But none of that is relevant as to how I approach the model output, which in my very simplistic manner, is based purely and simply on a meteorological analysis. Preferences and deliberate bias are no go areas.
  27. 50 likes
    Indeed Nick. With a strong signal for -ve U wind anomaly developing through the Equatorial Pacifc in the next few days, it's not so hard to see where this is coming from. That's centred on 120w which gives a strong projection to a MJO phase 8/1, regardless of what the wheeler Hendon plots show right now. GFS also suggesting a net easterly U wind anomaly through 20N and 30N across the Eastern Hemisphere at the end of the month giving a classical Nina look the atmosphere. That should engender a low AAM base state, weak amplitude GWO phase 2, which favours ridging to the North-east Atlantic. Interestingly should also set up a strong +ve frictional torque, and precursor to amplification later on in the month. With the configuration of SSTAs in the west Pacific and Indian Ocean still favouring convective anomalies over the Maritime Continent, would expect to see downstream wave breaking favour a low frequency patter of themain lobe of the polar vortex displaced slightly west and south of Greenland which suggests we might need to correct that ridge position further east over time. So whatever transpires wrt ridging to our NW and north over the day 7-10 timeframe (and reload over the northerly really well advertised in eps tonight, as essentially it has been the case for several days now), my eyes drawn to the north-east in the extended. Back that up with a cold, often anti cyclonic period in the medium term, you start to build a case for a below / well below monthly outlook. < Alistair - perfect timing!
  28. 49 likes
    Would normally not put a one liner on without charts - however given the paywall status of the EC Ens and clusters, all I can say is think - weeklies. Today will be a good day The roller coaster is firmly back on the tracks and heading for the winter theme park.
  29. 49 likes
    Very very interesting situation. I'm at work and away from my links, but I had a quick scan this morning before jumping out the door, and left with these thoughts: 1. Modelling of the azores high is going to be problematic. The record spiking of the current mjo is creating anomalously high westerly additions which currently sit nearly 2 standard deviations above the climatological norm for this time of year. We know this is working against our Nina background and as every day passes confidence grows that this nino style imprint is substantially gaining the upper hand. For the azores high this is very bad news: the sub tropical easterlies are falling and will continue to fall, and support for the azores ridge will begin to collapse. The spike is so great I wonder whether the modelling will nail it precisely, and the GFS in particular has a known bias against these setups. Long and short of it - I expect the azores high to be overmodelled over next week and more reduction south and west to occur. 2. Knock on effects of this are a greater chance of some milder air creeping into the mix BUT also a greater chance of precipitation. Cant have it both ways. 3. The modelling of stratospheric wave 2 impacts is also growing in substance. Some fabulous graphics out on twitter yesterday showing wave breaking against the Scandy/Russian block slicing straight through the vortex and giving us the almost perfect split... with high pressure in control to the north and a vortex shard skimming southwards to be placed over Europe. This is a medium term impact - GP nailed the timeline in a post not long ago on the strat thread as week after next, with impacts to be felt between 1 and 3 weeks afterwards. This means right through the month and possibly into March. The fact that CFS has now called a cold Euro continent for March suggests one model at least sees the vortex damage to be long term - though never take that as gospel. However its good to see. 4. Chio commented recently also that the vortex split looks to be trop led rather than the more conventional downwelling event. I have to tread carefully when talking about the strat cos my knowledge lags a long way behind others... but a trop led event, to my eye, adds longevity to the setup particularly given the climatological tendency for the vortex to wane the closer we get to March. It also allows the effects of the split to be felt much more quickly. Strat experts - please jump in and correct me on this if it is a wayward view.... Bottom line? Double whammy (perhaps linked double whammy?) of major MJO event and strat split (with possible reversal but that would be jumping the gun a bit...) gives is a chance of a sustained spell of that "perfect" scenario for western areas: entrenched continental cold sparked off initially by falling AAM in northern latitudes allowing a block to build combined with decline of azores influence followed by reinforcement of the cold as a result of the split vortex. All this then setup against a westerly flow off Canada that is already bitterly cold thanks to the season's tendency of the vortex to set up shop over the NE American continent and ongoing expectation of these fronts bumping into the block. It's potential nirvana. For eastern areas the strength of the easterly flow will dictate depth and extent of streamers (if they form) and there is always the chance of a Feb91 scenario with a front spawned from the south heading north. Can anything go wrong? Of course. That record breaking MJO could collapse in the face of strong Nina background forcing... but as said at the top: this is looking less and less likely as each day passes, and we are a lot better off already than we were in December when it collapsed previously. We could also get a sudden burst of solar activity - there is a theory that his is what did for the infamous Dec 2012 non-event. but right now the sun is extremely quiet. Long may it stay that way - enhanced solar input would pep up the jet and threaten to push the block back east. Or the forecast split vortex could fade - remembering particularly that it is at least partly dependent on the MJO creating the trop pattern to create the wave breaking in the first place. Treat the MJO with kid gloves - we need it well looked after. :-) I'm optimistic - though I tend to be optimistic in cold scenarios and that probably skews my judgement a bit. However the blocks are all in place for February to deliver... and significantly perhaps for this to be a long term event rather than a 2-3 day blast. Bring on that cold front on Tuesday, watch the azores high fade, the scandy block push west and then bumpers begin to approach and slide. Friday's ECM - a long way off admittedly - has the makings of a decent event occurring over already cold ground and entrenched cold aloft. With luck the south are about to get in on the act at last this winter.
  30. 48 likes
    The 00z EC ENS to d15 and clusters look anything but mundane to me. Markedly below average TMax against climatology (taking Reading as an example).
  31. 47 likes
    When this cold spell finally ends, will that be a Brrr-exit? Here's my take on the evolution: Gradual increase in North Sea streamer production through Monday with an episode of heavy snow moving into northeast England late Monday and spreading to central counties by Tuesday, widespread near-blizzard conditions in Midlands, Yorkshire and northeast to Wednesday, more isolated streamers in southeast but some locally heavy. Then this intriguing look of a looping moisture-laden low scraping into the edges of the cold and possibly making slight inroads into the south briefly with mixed precip but heavy snow likely to develop across large parts of southern England and Wales towards Friday 2nd. This could turn into a blizzard-like storm for Midlands and Wales as North Sea streamers are integrated into precip shield. Looks like a possible reload early next week. These are certainly stunning charts that, if they verify, will produce weather to rival anything recorded in the past, at least the inter-glacial past. There may have been better charts around 18,000 B.C. but somebody erased the archives.
  32. 47 likes
    Morning! If there is one thing that sums up the current state of model output it would be the following…. Yup it’s at a crossroads and this is particularly fascinating as I will go into some technical detail below and how this is relevant to the model output. Hopefully this can be clear to other members and it will give an idea of what I am looking out for. Background So, first some context…. The UK winter is moderated by the Gulf Stream, warm ocean currents move north from the tropics and help prevent the UK from being as cold as somewhere like Moscow. The diagram below shows a picture of the ocean currents. Warm air directed to the UK from Gulf stream Now interestingly there is evidence to suggest this is slowing down which generally should mean a negative feedback in the northern hemisphere due to a decrease in heat transport. Just one problem… the strengthening of mid latitude highs and deepening of polar lows means the Eurasian continent has warmed substantially during the winter months. Trends in SLP since the 1950s (Gillett et al 2005) So where is affected by this negative feedback?, well the below diagram clearly shows one place. The central North Atlantic. Looking at warming trends in the figure below we can see that this region has actually got cooler over time, in stark contrast to almost everywhere else. IPCC, global temperature trend from 1900-2012, spot an anomaly? This is now referred to as the North Atlantic cold blob and I believe it hurts our chances of cold winters. Look at the last 4 winters. These have been dominated by more frequent then usual westerlies and the North Atlantic SST profiles are seen below. 2013/14 2014/15 2015/16 2016/17 February 2018 - See a pattern developing here? To get a cold anomaly in this region it requires cold air from NE Canada to pour into the North Atlantic…. And how is that possible? Yup with a polar vortex camped to the west of Greenland. So with a slightly weaker AMOC and an intensification of mid-latitude highs we have a pretty poor combination of factors for UK cold whereas in the US it ain’t so bad. That is why the US still sees these big cold air outbreaks from time to time. So how can we break this sequence? Well other factors also influence our climate, extreme MJO phases, low solar activity or a dramatic slowdown of the AMOC can do it. In December 2009 this is precisely what happened. With the increased warmth nowadays, if this is directed to the arctic it can really shunt the PV for long periods of time. Just look at the anomalous arctic warmth in 2010. December 2009 - Bullseye Indeed this pattern persisted until January 2011 but a very strong La Nina signal prevailed for that winter later on. Other alternatives are extreme MJO phases (the phase 7 signal recently helped build Scandi highs to our east, though they weren’t that strong) and deep cold pooling just to our east. However the warming arctic and more intense mid latitude highs makes this more difficult. Just look at the last 4 Februaries + this January and their temperature anomalies. Continental cold can stop the Atlantic in its tracks. In 2013 we got lucky and February the arctic was actually colder then normal. This cold air spilled into Scandi and in combination with the SSW event, this was allowed to stem the Atlantic tide and as a result we got a very cold March. Battleground in the model output So where does this lead? Well its of my opinion that we are seeing a more volatile NAO because positive phases are amplified by trends in mid latitude highs. Negative phases are amplified by increased warmth heading to the arctic. Just look at the NAO values for each winter since 2006. 2006/07 + 1.81 2007/08 + 1.34 2008/09 - 0.31 2009/10 - 2.71 2010/11 - 0.84 2011/12 - 2.08 2012/13 - 0.58 2013/14 +2.05 2014/15 + 2.04 2015/16 + 1.84 2016/17 +1.12 Bear in mind any mean value over one is considered extreme So Yup we are at a crossroads, will the organised polar vortex drown out the SSW again? Will there be more cyclonic westerlies? The current SSW event is fascinating because of its location shown below. Additionally if the pendulum swings the other way then we could see the strong negative NAO months make a return with an exceptionally warm arctic/Greenland. It seems conditions are becoming increasingly favourable towards the cold air in the North Atlantic persisting in the winter months and more factors need to come together to overwhelm it. We came so close early on in the winter and if this had succeeded then the winter NAO I believe would have turned strongly negative. The critical point highlighted below. I believe the struggle to overwhelm the North Atlantic cold pool is what is leading to some of the disappointing runs from the ECM. Will we succeed this time though and cause the see-saw to swing the other way? I believe if it does, it will help next winter too. At the moment its hard to tell, the ops look poor but ensemble means are more intriguing. GFS ECM Hope you enjoyed reading my thoughts and have an insight into what to look out for in the model output! This is an educated guess but it is what I believe. Quicksilver
  33. 47 likes
    Please excuse me once again quoting my own post - but continuity shows that there is an obvious clear stand-off between the models on the way ahead from this weekend with different model interpretations of how tropical>extra tropical forcing manifests itself in the forthcoming period. Which in simple terms determines the amount of amplification available for cold air advection sustaining to any given time My suggestion of keeping powder dry and an open mind in terms of these differences looks to be relevant well beond the shorter/medium term. There are going to be plenty more NWP skirmishes to come beyond the early question marks of what follows straight after this weekend. Best not to overreact to the GFS interpretation which is indicative of upstream tropical forcing being more restrictive at face value, at this time - and as a consequence delivering a much more 'La Nina-like' solution with quickest return of Canadian vortex induced downstream cyclonic energy. I see that Catacol has provided a thorough summary of the technical background to this, and which follows a pm conversation I had with him this morning, so there is little further for me to add to that.. But the implications of forward moving momentum in the tropics mean that processes start happening which in time propagate to the extra tropics - and these become vital to how the longer term plays out. One of those starting processes that accompanies an upward shift in angular momentum tendency is a corresponding upward shift in frictional torque tendency in the tropics - and which has consequences over a considerable period of time in terms of what it can do to the longwave synoptic pattern in the extra tropics mid and higher latitudes. What is this frictional torque and what exactly is implied by it? Atmospheric angular momentum in simple terms refers to the amount of turning force in the Jetstream. The balance (or budget) of AAM is determined in very simplest terms by the net amount of both easterly and westerly wind-flows that are present at any given time in the atmospheric circulation. If there is excess easterly wind inertia in the global jetflows, at any given time (c/o La Nina trade winds propagating to the extra tropics), then this has the effect of lowering angular momentum tendency and producing a -ve frictional torque at the surface. The frictional torque refers to a pressure differential created from the point of where easterly winds are added and westerly inertia is scrubbed from the atmospheric circulation. Divergence across the tropics, where the trades are found leads to the spin-up of sub tropical anticyclones which align from west to east circum-globally. One of those sub tropical ridges relevant in our sector is obviously the Azores High. This has, as expected, been a prominent feature of this winter so far and has meant that cold air incursions have been based on mid latitude amplifications. We see this coming week how the Azores High plays it part as an amplified mid latitude feature once again in introducing another cold incursion to the UK. The longevity of this phase comes down to what happens in the tropics over the coming medium term period, and pertinent to the discussion in this post, how much frictional (ocean) surface torques and extra tropical (mountain torque) mechanisms can be altered (upwards) by increasing angular momentum tendency. The consequence of a sufficiently robust eastward moving tropical signal is that the subsequent eddies in the windflows (produced by the significant alignment of tropical thunderstorm activity on a macro scale) tend to flux poleward with time. This means that an amplification mechanism is triggered which follows the principles of a stone thrown into a pond, and the ripples spread out according to the size of the stone and also how far away from starting base the stone is thrown, So poleward motion of flux, +ve frictional torque tendency in the tropics can lead to +ve mountain torque tendency in the extra tropics according to the size of the initial 'splash'. The size of the splash of course relates to the size of the tropical forcing advancing eastwards through the tropics, and if there are differences between models as to the strength and longevity of that signal, then the consequent downstream amplification signal is going to vary from one model to another What of the implications of +ve frictional torque in the tropics and +ve EAMT in the extra tropics? The shorter term product of a good amplification signal is of course the ability of the initial amplified Atlantic ridge to extend into Scandinavia, with a split jet that enables 'appropriate' jet flow over and under the ridge to support it, and enable the 'horseshoe' configurative return of the jet back SW'wards to assist cold air advection this way. But as suggested in the stratosphere thread by chiono, an H500 pattern being one of Scandinavian heights and upstream EPO ridge is one that aligns itself suitably to externally pressurise the vortex. This has, as stated, extended term implications for potential SSW much later in the month/ early Feb. But also there is the poleward effects of +ve torque mechanisms to perturb the vortex internally as part of a tropospheric tropical>extra tropical mid/higher latitude>stratosphere disrupting mechanism. The wavelength/timeline of a programme of +ve frictional torques implies a dismantling of the sub tropical ridges through westerly winds added through the tropics by eastward moving convection to scrub the La Nina easterly trades from the atmosphere that underpin those ridges. That is in addition to lagged effects of extra tropical +ve mountain torque effects that deflect warm air advection into cold vortex segments If a programme of higher heights and a -ve AO profile is to be created by a combination of poleward fluxing +AAM anomalies as well as a wave 2 activity response from a height profile each side of the pole, then the domino to fall is the weakening of the Azores High to facilitate undercut and remove the +NAO profile. It is this that restricts us to what we see this weekend that depends upon maximum amplification of the Mid Atlantic ridge to achieve a Scandinavian High, to one where the Pacific forcing pattern, that is a-typical of La Nina, can override the base state forcing and engineer maximum downstream capital c/o split-flow with enough energy going into the southern stream to undercut heights to the N and NE. This happening in the absence of a sub tropical ridge, that is both a natural feature of a La Nina pattern, but is also counter-intuitive to developing a -NAO to assist backing cold air west c/o of a -AO profile I suspect however the on-going shorter term Atlantic ridge>Scandinavian ridge plays out vs Canadian vortex, this will be a cat and mouse theme to dominate January and we will be relying on the Azores High playing ball according to (and dependant on) the relative level of atmospheric angular momentum - and to the extent the Nina trades are mitigated to allow undercutting energy. The undercut has remained elusive this winter so far in the midst of quite an amplified mid latitude pattern Can the extra mile be achieved Very long post again, but so much to watch out for - only just ahead of the next ECM...
  34. 47 likes
    I suspect we may have to go through a sequence such as this to get to the possible upsides that exist later in December More seriously, and with promises made there will be no more halcyon day jollity I think some form of mobility is at least conceivable, for a short time, to follow this quiet surface cold anti-cyclonic sequence. I would be extra cautious though of reading too much into intra day modelling suites, especially but not exclusively GFS operational output, which will be susceptible to overdoing a reaction to some short term momentum transport across the pole as the vortex briefly tries to establish itself at the native home at the same time some fall back in angular momentum occurs ahead of the renewed eastward progression of tropical forcing, The upstream.. downstream response might well be adding just a tad little extra energy into the northern branch of the jet stream. On that basis alone - there is no reason whatsoever at all for concern, just yet, at such an evolution - should it arise. This post really is just my own reflection of the theme Matt sensibly laid out earlier, but the question mark following the upcoming sequence of weather (extended anticyclone or partial mobility phase) turns to the subsequent vortex spilt at, hopefully, a similar time as eastward movement of tropical convection forcing occurs to Indonesia, as mentioned above and discussed and explained in great detail yesterday and previous days, and the associated uptick in angular momentum tendency to re-amplify the pattern and fully exacerbate the vortex split and instability. The timing factors/verification importance of these were stressed as far back as last week in terms of the 'make or break that Matt describes today Important in terms of additional amplification and assisting further stratospheric destabilisation and the goodies suggested by EC monthly, with support from UKMO. I'd repeat what was said last week - tropical convection is not handled well by computer models at any distance. Assessing OLR anomalies and areas of cloudiness over the tropics provides a more 'in the moment' assessment of progress of tropical activity, and gives an extra handle on development So, there is no reason yet to suspect so, but *if* there was a delay or no show of this amplification programme from upstream, that would imply that angular momentum tendency will remain more supressed and the ramifications of that would be flatter longer term outcomes, greater polar jet energy and some reprieve for the vortex at a time when it looks most susceptible. In that sense, the lessons of frenzied expectations of Decembers like 2012 loom larger in terms of joyous ECM monthlies. On that occasion however, I seem to remember that the UKMO modelling was much less bullish and did not support the freezing easterlies identified by the ECM. So its good that there is some cross model agreement this time for a cold blocked pattern through the second half of December. So this is not to suggest a repeat of that 2012 analogy is likely in the same way as, to the even greater extent at the other end of the scale, the December 62 analogy is likely to revisit. A bit of fun that was, which I am sure most realised. Though, beyond the banter, the same intended point remains as yesterday evening - the frustrations of an apparently stubborn Euro High are not necessarily an unrequited road to nowhere .... I think its a case of continuing to keep obtaining the best data to hand at the time and making the best judgements based on that. Such (balanced) analysis remains in flux as the atmosphere is - and evolves accordingly. The best professionals, let alone keen amateur enthusiasts on here, can do no better than this. So best not to keep fretting, poring over intra day model suites, worrying why there isn't yet a Greenland High at t360 to t6000 - and try instead to only see round the extra corners as they come into view and provide the intelligent answers we require For my own part the Global Synoptic Dynamical Model (GSDM) continues to offer personal challenges, but ultimately highly useful guidance and reward the more I understand about it, as to where the models may head next. Hindsight over the coming days and weeks will have all the answers as usual, but whatever the outcome, there is always something to learn - and (in the event things don't work out, (no reason yet to say they won't) it is this that should sustain and (hopefully) not instead some unproductive reputation-ignited fire-fight over who correctly or incorrectly forecasted what, when and where. Breathe and enjoy
  35. 46 likes
    Evening All- Today is probably the first day that many will start to take notice of the ECM ( & of course the UKMO which dovetails nicely in together at 144 ) What we have here is a clear case of a model backing away from the initial proposed continuation of the zonal flow to something potentially very amplified. This transition is clearly demonstrated in the modality change of the AO taken from the 12z ECM operational. It has to be said & earmarked at this very early stage that no-one can be certain of any outcome whether that be some deep seated easterly or a flattening of the pattern with no cold. The ECM ( & GEM ) are picking up a transition signal & at day 9/10 may well continue to move fully through that transition to a scenario of what want ( a la 2013 ) or indeed stop short of Nirvana. Whilst he was ridiculed on here for all the right reasons certainly the Ian brown phrase of if you cant see the train then its not coming- Its great to see positive developments over the last 24 hours at 8/9/10 whilst the interim continues to show periodic snow events at localised levels over the UK... An exciting few days to look forward to - All aboard the chase as it starts inline with the crimbo run in......
  36. 46 likes
    If we take the ECM at +168 two days ago And compare it with the ECM +120 from tonight You can clearly see that as we’ve got closer to reality, the model has; 1) Underestimated heights around Iceland area 2) Has started to disrupt the trough to our west more, it is more negatively tilted and a little more elongated. 3) heights in Europe lower than previously modelled If that trend continues in the next two days and the same for the subsequent frames after this, perhaps Day 10 will look a lot different come T+0 than it does now. This is the same for GFS too, not just ECM. Uncertain outlook but certainly upgrades in the mid term from the models. UKMO pretty solid. Going to wait a couple of days at least yet.
  37. 46 likes
    We are seeing the impact of phase 7 MJO in the forecasts already. Chio is, of course, right: we need the atlantic energy this week to create the blast that rips the vortex in half as it bounces off the block over N-Scandy... so very short term irritation for much juicy long term gain... but even in this scenario we are seeing falling momentum encourage the resilience of that fledgling block - and while the vortex is blasted we have cold enough air in our vicinity to see some snow and cold even in the face of that atlantic wave. This is a really good sign - the block is building even before the vortex gets hammered - how fast will it continue to build and strengthen once all the activity far aloft starts to spin the wrong way and fall far off centre? This initial strengthening is all pacific led. Some have seen some snow today I think. Some yellow warnings out.... some showers to come even to western parts on Tuesday. But it really is only the beginning. With part of the vortex set to drop over the NE US and consequent certainty of some atlantic lows being spawned off it.. and the near certainty of a strong block to our NE there is a very good chance of some proper battleground snow and channel runners sitting alongside east coast convection activity. Not every day of course... but it only has to happen once for lying snow to hammer temperatures even further down with a cold airstream in place... and for once the slightly stronger sun in February might do us some big favours in encouraging some pep in the flow come month's final third. Oh lordy. I havent felt this excited about a weather situation since opening my curtains on Feb 7th 1996... but that is a whole 'nother story.
  38. 45 likes
    Its only an island if you look at it from the water A textbook example of where an amplitude MJO wave lead the atmosphere on a surging poleward +AAM rally and which in turn created a bitterly cold high latitude blocked pattern from the first week of February and which lasted well into the month was in 1978 January 1978 closed out having featured a lot of the cold zonal pattern which has featured through quite extensive parts of this winter, and which favoured northern parts of the UK mostly. The very distinct difference back in early 1978 being that the global atmospheric circulation was pre-disposed to a Nino-like forcing which was setting in place a tropospheric>stratospheric pathway that was conducive to supporting poleward +AAM anomaly wave breaking. A reflection of how close we have actually come to achieving a properly cold winter in 17/18 - if the a-typical La Nina east based Pacific tropical forcing had prevailed and kept angular momentum in the elevated state it began the season. GLAAM: globally averaged angular momentum: Jan Feb Mar Apr May June Jul Aug Sept Oct Nov Dec 1978 1.75 1.75 1.54 0.81 0.17 -0.07 -0.27 -0.26 -0.22 -0.20 0.20 0.93 For info http://www.esrl.noaa.gov/psd/data/climateindices/list In a year as a whole that was to all intents and purposes of a neutral ENSO persuasion overall, I bolded and underlined the +ve GLAAM figures for all the winter months, and note how they are all book-ended early and late in the year. A further clue there how the classic finale in Dec 1978 evolved through further tanking angular momentum set against the base state, and renewed -AO and -NAO But back to what evolved in Feb 1978. Soaring +AAM induced the Global Wind Oscillation into the El Nino attractor Phases 5 and 6. The synoptic pattern moved into the sort of classic Nino pattern that can occur when the stratospheric field is weak and unstable (December 2009 is another very good example). Heavy convective snow showers for many, widespread severe frosts and culminating in those spectacular 'battleground' blizzards in the SW as the Nino feedbacks from dateline MJO forcing induced the southern stream and classic undercutting -NAO. Anyway, the point of all that nostalgic snow-fix is to illustrate the importance of having an co-operative tropical>extra tropical>stratospheric poleward loop in place to buoy the troposphere and to complete the task in terms of a stratospheric vortex which is vulnerable to such +AAM forcing. The skeleton troposphere/stratosphere pattern this winter at face value has been vulnerable to such forcing, but has so far achieved what would be considered a get out of jail card. Clearly, with the overriding La Nina forcing proving too strong, we have been lacking that missing link in the middle and why any high amplitude MJO wave, that becomes possible with the warmer waters in the western Equatorial Pacific, needs extra tropical co-operation to enable the troposphere>stratosphere pathway to be completed. In synoptic terms, effectively mimicking a wave train that is more akin to an El Nino and induce jet flow away from the polar northern branch, with weakened sub tropical ridges (that have been strangle-holding the on-going pattern), and instead energy flow into the southern stream assisting an -NAO. The coming month still holds a lot of interest - and one eyebrow at least is now being slowly raised. There is no denying the suggested strength of this MJO wave, which has actually been upgrading in prospects with time - and with signs emerging that this Nina maybe has been having its last proper 'hurrah' as sub surface waters in the Equatorial Pacific return closer to normal, then its not impossible on the back of the latest still increasing tropical momentum, that a significant +AAM surge might not evolve to lead the trend. In order to support that hypothesis however, some conclusive evidence from the extra tropics is required, and would be highly satisfying to see over coming days to prove that the undoubted momentum in the tropics is set to start putting in place the decline of this La Nina. To put that decline in its perspective, that means that the expectation is to weaken towards neutral heading into the Spring. But in that sense its not the base actual state that matters - its the direction of travel that would unquestionably make tropical/extra tropical co-operation more possible than it has been proving, and complete what has been the missing link. Lets hope its not too little too late - however if the direction of travel firmly becomes one of poleward +AAM that transfers on a sustained pathway out of the MJO tropics, then the chances of turning a frustrating pattern into something more interesting definitely increases.
  39. 45 likes
    As usual there are different ways of looking at this. A few things: 1) We have been able to successfully trace the end of one cold snap in mid January to plot (in advance) the development of the next (albeit its not the 1991 redux one might hope for). That has been possible, through some collective effort and different methodologies converging. As a practical community exercise that illustrates one of the benefits of being a member of a forum such as this - and far too often it gets obscured and not acknowledged as much as it should. The rollercoaster element might provide the excitement when things look good, but it also can serve to detract the community positives when the solutions on offer do not appeal to the eye of the audience 2) Participating in the regional thread over the coming days will make the most of the snow opportunities there are to come, so it need not be a let down at all. We cannot make it snow. let alone everywhere, and not to desired quantities, but its still possible to make the most of what might come. Otherwise all the chasing since mid January (for those who managed to see snow) has no reward away from the computer. So best head out take pics and enjoy it while it is here and then report back 3) GP has posted in the technical thread and it makes complete sense as reflected by NWP. I spoke the other day about the need for the tropical signal (the nucleus for downstream amplification) to work its way through to the extra tropics and only then the full amplification potential downstream can be assessed. Clearly from the downstream pattern that has come into model consensus today, the amplification potential suggested by the Pacific forcing is not apparent to that extent and I had been thinking yesterday evening there must be (again!) a destructive I/O signal not allowing it to fulfil expectations. In data terms it doesn't seem much at all, but in terms of ripples in a pond stemming from the smallest pebbles, they nevertheless spread far and wide. The timelines I have referred to are clearly set to be at the longest end of the envelope, but then estimations can only be as good as the last data set. This certainly doesn't debunk the initial thinking, but it does mean we will not get the more seamless movement from one cold evolution (Scandi High) to the next that seemed possible - and it explains why the retrogression signal (which had been responding to in line with expectations) has faded. If anyone thinks it should be due, I will accept any responsibility for heightening any expectations by speaking of converging signals producing "the icing on the cake" but then I will also stick to the fact that this had been quite feasibly reasoned (and believe the fullness of time will show that) 4) The interpretation to take from all this in GSDM terms suggests that the Global Wind Oscillation orbit will be much shallower amplitude than anticipated until the destructive interference from the tropics diminishes. I find it very frustrating that such a compelling tropical and extra tropical amplification signal has been diluted and delayed - having coming so far so well. Hand in hand with a split vortex solution rather than a displacement, some of those highly appealing ensemble solutions up to yesterday would not have stayed in the virtual world.... 5) However there is still the compelling real time signal spoken of in detail previously of rapidly rising angular momentum tendency. The MJO signal might have had an unwanted intervention, but it has not gone away. Lagged by the tropical glitch, rising frictional torque and then mountain torque still cues up the expected amplification - but destined for a cold finale to winter and usher into Spring. Whether the whole audience welcomes that or not is completely subjective of course. 6) Finally, what we can deduce from all this is yet another proof exercise of what I often repeat. The teleconnections do work, but they do not always evolve to optimise the most desired result. But then that has always been the point - this forum has a natural bias, the science of meteorology has no bias.
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    Only for those who lack a sense of humour. Keep at it with the Sidney references and pics please Frosty, most of us appreciate it. As for the models, still too early to call. I think that the final outcome will be a compromise between the ECM and GFS but I'd love it if the ECM came to pass.
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    As an ex forecaster it is easy to be critical but I do feel that all of us, me included, are guilty of our recently gained knowledge of background signals. These have always been there, they have not just been invented. Simply that we are all starting to see meteorology in a deeper light so to speak. A little knowledge is dangerous especially when coupled with knee jerk reactions to what appears to be changes in what some of the drivers are currently indicating. I wonder how much belief would have been shown in them prior to the 47 winter or the 62-63 one if they had been available and understood in those days. Comments like ‘once this or that weather type is occurring… ‘. Both those winters had mild, even very mild periods prior to the start of the intense cold and snow. About the only thing that is known for sure is that the northern hemisphere has a far different looking upper air pattern to this time last year. Perhaps this may mean that our subsequent weather will be equally different. No one knows for sure. How about we all just sit back read other folks posts add anything we feel may add information, stop belly aching about models or digging at others because they have a different view and enjoy the weather. Is that not what the large majority of us joined Net Weather for? To put a model input here, using my trusty 500 mb anomaly charts and they do not show anything to suggest a deep cold set up in the next two weeks. Neither do they show a raging Atlantic although that is perhaps, on the past 24 hours outputs, from not just the anomaly charts, a slightly better bet post 15 days? All 3 I use continue to show +ve heights in the more northern areas of their charts. Just how this will turn out in 7-10 days time I really have no idea but it hardly warrants some of the comments in the model thread today. Links ECMWF-GFS this morning http://mp1.met.psu.edu/~fxg1/ECMWF_0z/hgtcomp.html NOAA last evening http://www.cpc.noaa.gov/products/predictions/610day/500mb.php Last night NAEFS http://www.meteociel.fr/modeles/naefs_cartes.php?code=0&ech=240&mode=0&map=1&runpara=
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    Keep watching the angular momentum budget updates! The disconnect between ENSO base state and atmospheric circulation response, as discussed in recent posts in quite some detail, has been ramping up to something of considerable interest and significance in terms of the much anticipated return to a -AO discussed on these pages. The question, presently, is still more about timing, rather than whether it will happen at all. Whilst the central Pacific Ocean registers weakly negative SST anomalies, the atmospheric circulation refuses to perpetuate the ENSO cycle to develop this profile and enable a coupled ocean/atmosphere response to reflect in NWP modelling. The 30 day SOI rolling index has continued its plunge since early October and reflects that considerable disconnect. The Global Wind Oscillation has broken through the "psychological orbit barrier" into a low amplitude Phase 5/6/7 cycle that is representative of current El Nino atmospheric responses - and most definitely not La Nina whatever the Pacific ocean SST's suggest. This in response to tendency in relative angular momentum starting to ramp up as the MJO heads through the Pacific, as heads-up has provided in previous posts. Notice the orange shaded westerly wind additions heading up from the sub tropics The more that this response is perpetuated by sustained additions of westerly winds across the Pacific, the less chance there is of the synoptic pattern adopting a Nina profile with anomalous ridges in the Pacific and Atlantic in the winter, and the less that net polar flow will be inclined to overspread that ridging in the northern branch from upstream - especially taking into account a recalcitrant polar vortex to augment the effects of very weak zonal flow. Of course the pattern ebbs and flows, but its the trend as winter wavelength changes rapidly approach, and force a coupling of the Annular Mode (AO and NAO) heading more and more to the New Year that will make the present signals relevant. Much as happened in autumn 2009 (in the context of atmospheric responses against an ENSO state that had been weakly Nina inclined within a neutral ENSo base).. The seeds of increasing atmospheric angular momentum built up more and more amplification into the atmospheric circulation (through both the tropics and extra tropics) by adding more net westerlies tthan easterlies to the atmosphere. Westerlies that tend to head poleward with time, and the resultant amplification eddies within an unstable troposphere and stratosphere profile create higher latitude blocking profiles In that context although we are certainly not suggesting another winter 09/10 per se, at least we are encountering the exact same atmospheric processes as 2009 - with amplification feedbacks that lead to blocking patterns over a period of time. Remember when these charts arrived by mid December.. On that basis, take the MJO pulse across the Pacific as a clear signal of the atmospheric disconnext in itself (a coupled Nina state would not entertain orbit through the Pacific without dying a death in Phase 7) but more importantly the consequences - which are an amplification feedback that should be poised to take advantage of an unstable stratospheric profile through December - and further ahead to the start of the New Year. Accrued feedbacks that imply an entrenched -AO profile that couples with the NAO as wavelengths changes do the rest. Take any November muck and sludge that comes and keep watching how the atmosphere jives with the stratosphere in the meantime. That's any net weather time booked for me anyway
  43. 44 likes
    To be fair @DiagonalRedLine that is not model related could I kindly ask you to post in the appropriate thread in future. If not it may be removed, or we will be forced to remove your posting privileges many thanks banter team
  44. 44 likes
    This next 'evolution' is all about the speed & deceleration of the pacific jet & how far east the Low at 168 gets & how the 'tilt' of the low supports the cold Not sure where this cold for +10 days or 12/15 days is coming from. Its day 7!!!!!! The UKMO ( as already highlighted ) has been performing much better than the GFS in terms of non bias Eastwards, & as we stand tonight would be poised for the greatest advection of cold @168- Ive annotated the 144 charts to show the differences showing why they may or may not 'project east' hint hint.... In Order -UKMO/ ECM/ GFS The UKMO is the slowest & most amplified with a negative tilted low & support for a greater blocking wedge ahead of the low pressure, this run would project the coldest outcome @168 >192 with the most amplified trough axis & a high likleyhood of the mild 'bump' of warmth hitting the UK 192/216 - or at least seeing more of a glancing 'slider' impact across Ireland / SW. GFS is positive in the tilt indicating more forward speed & less block, which to a certain extent is supported by ECM with its neutral position, ( Glancing at the ECM 12z mean - looks more UKMO ish ) Expect ECM op to be mild outlier day 8/9/10 So tonights summary would be similar to the forecast from 3-4 days ago where we say the UKMO day 6 chart almost spot on- Which is..... UKMO / ECM blend with the low, maybe UKMO to negative, ECM to neutral so the middle ground- GFS to far east with its 'positive tilt' look for that to correct... The upshot of all this will mean the -8c line is further south & west 168-192 & also atlantic inroads into the UK less progressive. At the moment the model theme ( from 120 ) is more indicitive of cold zonality with the treasure at the end of the rainbow day 9/10 however UKMO indicates that the day 8> 9 blip could actually be a slider snow scenario... Have a good one S
  45. 44 likes
    The above summer forecast verified reasonably well in most cases, the prediction implied a top ten outcome and in fact the summer was around 3rd to 5th warmest on record depending on which data you used. The CET predictions of 16, 18 and 17 compare with 16.1, 19.1 and 16.6 for an average error of 0.53 C deg, and it has to be kept in mind that August was running close to 17 until around the 23rd with a very cool finish. The overall prediction was closer, with an average error of only 0.27 C (17.0 vs actual of 17.27). It was a dry summer in many parts of southern Britain and southeast Ireland. The magnitude of this drought was probably underplayed in the forecast. As for North America, it certainly did turn into a scorcher of a summer in the west with widespread fires in western Canada in particular. We were dealing with noxious smoke on an epic scale for much of August (although I was away on holiday in clearer skies down south) and the first week of September before the activity finally subsided. The tropical season has not been keeping pace with the forecast although it could still work out fairly close, and Michael alone is worth several ordinary hurricanes I suppose. ... well, I won't make a big deal about this forecast because basically I think almost everyone expected this sort of summer after the spring blocking, so it is now on to the winter of 2018-19 for the next instalment ... Long-Range Outlook for Winter 2018-19 As always, my forecast is based on a blend of traditional concepts and exclusive research into "index values" on the assumption that at least some variability in the climate can be linked to variations in the solar system magnetic field (a complex response to relatively small changes in solar wind output and effects on the earth's linked atmosphere and magnetosphere). It is looking quite cold compared to normal for Britain and Ireland, in particular later December and parts of January. However, this appears to be dependent on a strong jet stream either shifting far enough south or relaxing for periods of 1-2 weeks, and the intervals between the cold spells could be quite stormy at times when the jet stream is roaring at full capacity. The research index values in particular go far colder than I have seen them for the past several winters, indicating many analogue cases that were very cold winters. Looking through the analogues, I find that periods around late December into early January, and mid to late January, were favoured for the coldest weather. This is also favoured by assumptions made about lunar modulation of the pattern, which is how I have come to see the lunar influence, not as a driver so much as a shaper of larger signals from the other players at work. Another consideration is that we are well into a prolonged solar downturn and so there's nothing in the larger solar-weather paradigm to contradict the notion of this being a colder than average winter. We are in a similar position to the period 1819 to 1823 which had numerous cold winters but it's not a guarantee by itself to be in this sort of regime. I've seen some discussion saying that perhaps this won't be the widely expected "big one" and perhaps we'll need to wait another winter or two, but I have no way of choosing which one is the big one from the coarse assumptions that one is forced to make using only a solar-weather paradigm. The past summer season in the central Canadian arctic was exceptionally cold. Resolute for example had no month warmer than the 1.9 average in July, and that is the lowest such statistic on record in recent times (the record began in 1948). This has been followed up by a large-scale southward movement of a cold anomaly over central Canada that has people commenting that winter already began in the prairies in early September, with snow often on the ground. This anomaly is almost bound to be followed up by a persistent trough around 90 to 100 W longitude. That in turn would favour west Atlantic blocking and a downstream trough between 10 and 30 W. Although that's a little west of the "sweet spot" for a cold winter in Britain and Ireland, I feel that it may be a high amplitude pattern that will induce Scandinavian blocking highs, and cold outflow from those despite fairly high 500-mb heights in western Europe at times. And the pattern could oscillate east-west enough to place the trough over Britain and Ireland at times. So I am predicting a notably cold winter but with high variability possible leading to alternating spells of wintry cold and stormy fast flow situations. Another factor that may prove significant is that energy levels will be highly concentrated near the full and new moons this winter, perhaps more so than has been the case in most recent winters. I expect this to translate into alternating periods of very unsettled, stormy weather around those lunar dates, and relatively long settled intervals between them. The settled intervals are likely to be the times when blocking will deliver the colder air masses from an easterly or northeasterly source. But there may be some tendency for the disturbed intervals to remain cold and turn more northerly. This could add up to considerably more snowfall in the heart of winter than we've seen for quite a few seasons, in contrast to last winter's concentration of snowfall near the very end of the winter season (27 Feb to 2 March was very snowy in some regions). I am aware that this represents a high risk forecast, especially given the tendency of recent winters to resist opportunities to establish potent blocking. So it won't absolutely surprise me if the result is some kind of weaker compromise where some cold and some snowfall develop but longer intervals remain relatively mild. I don't foresee a really mild winter being likely given these background conditions, and I do have concerns that the volatility may produce some exceptionally stormy intervals. This pattern may persist well into late winter and March may not see a lot of change from it, except that by then the energy level considerations will be more evenly distributed into four peaks rather than two per lunation. That separation during February may lead to a peak in snowfall since the peaks will be somewhat less supported and that could be reflected in a more persistent blocking pattern. As to the dates of the stormy episodes, those appear most likely to fall around 19-22 December, 3-6 January, and 16-20 January, and there could be heavy rainfalls in the south during some of those intervals as colder regimes are pushed back to the north at least temporarily, but as time goes on the chances for snowstorms likely increases with each of these windows, then towards the end of January it may be more of a sea-effect snowfall opportunity with the storm track pushed much further south into Iberia and the Mediterranean. During the anticyclonic intervals that are likely to peak between those stormy intervals, we could see some unusually low temperatures especially if snow cover has been established towards the transition from stormy to settled weather. In the run up to the winter, I would expect quite frequent mild and unsettled patterns with the colder synoptics taking their time to appear, possibly in muted form around mid to late November so that perhaps Scotland will get the first round of this predicted wintry regime. In North America, I am expecting a winter dominated by intense cold over central regions, often extending out to both coasts, and a generally depressed jet stream but with weak El Nino tendencies likely to lead to frequent and heavy snowfall inland from the west coast over the Rockies about as far south as northern New Mexico. Parts of eastern Canada may be unusually mild with the storm track tending to run north from near Cape Cod into eastern Quebec province. I feel like this may be a very rough sketch of a winter that may contain some really unusual synoptics and bring conditions that are rarely seen at some times, and those are difficult to anticipate so would just caution that various extremes may be tested at times. I don't think it will be a dull or boring weather pattern for most of the winter, in any case. For verification, I expect the average temperatures to run as much as 1.5 to 2 degrees below recent normals and for this winter to be one of the colder ones in the past thirty or even fifty, and colder even than the longer-term averages which run almost a degree below modern 30-year averages. I somehow doubt that it could be an all-time cold contender to match the summer because that seems to be very difficult to achieve with the ice margins being as far north as they have set up in the North Atlantic in modern times. But as we saw in December 2010, anything is still possible and there could be some intervals of record breaking cold.
  46. 44 likes
    A good post based on reasoning of which You couldn’t argue based on the information that you present. There is however the small matter of ‘human intervention & forecasting’ involved here as well as experience. That’s the difference between someone who chooses to solely rely on what a model says V someone who blends what’s a model says with ‘experience’ of said models & when they perform poorly, so whilst the data you have forms your opionion - all it does is reinforce mine which is model output + blend of experience. So let’s be clear from Day 1 I think both me ( & TEITS - when he joined the party ) have forecast a ‘decent’ continental Easterly to reach the UK -circa -6 850 or below - The timeline which as with most cold spells has slightly elongated due to model progression ( haven’t got time to explain now ) is still due Thurs / Fri. Let’s not forget all the ‘teleconnection’ crew decided it wasn’t going to happen - based on reduced angular momentum etc leaving just one or 2 going against the whole model suite. we now find just 2 days later the same model suites following just 1 model - The UKMO- which has forecast pretty much the scenario suggested from day 1 just spread over 1/2 more days. People seem to forget how bad the GFS & ECM have been in the last 2 days - here a typical incidence ECM last 3 00z 168>144 & today’s 120 Its Crystal clear the model has moved to the forecast scenario - Now examine the Debilt ENs same vein - No cold - some cold then hang in a minute - lots of cold. No point in posting the GFS as it’s still a day behind. So great argument - but your data is flawed & changing in favour of cold. My current thoughts hold Easterly / Southeasterly in situ at day 6-7 with a high potential of undercut not currently shown in the models. Best s PS ***everyone*** ask yourself 1 question * Why the Met office with every MOGREPs / ECM run / ENS suite available decide not to modify the T84 Fax chart away from the UKMO 12z raw data- answer: because they have confidence it will be correct—
  47. 44 likes
    It's time for some members to take stock of what they're doing, as there are so many off topic posts and it's totally unfair on those who want to post and read about the models. If you want to discuss the model output, this is the place. If you want to moan about the models then head over to the model moans/ramps thread: https://www.netweather.tv/forum/topic/86721-model-moanramp-thread/ If you want to talk about the winter in general, long range forecasts, tv forecasts and a myriad of other topics, please take a look in the Winter forum: https://www.netweather.tv/forum/forum/1-winter-and-general-weather-discussion/ If you want to have a personal chat with someone, please use the pm system. And finally, if you want to have a row with someone, please step away from the pc and chill out for a bit, as it's not worth it. Thanks!
  48. 44 likes
    Interesting to note that both the EC HRES and Control are similar but they are both definitely cold runs when compared against the ENS spread. Few other members support them but would have thought they are more extreme solutions. However, what is present which supports other 00Z DET runs is that the high and overal pattern is more amplified middle of next week leading to a greater risk of chilly, frosty weather. 6 members out of 51 support the evolution as per the 00Z EC within the clusters. Interestingly though signal growing (22 members) for a decent Greenland block by 216/240hr and a general -ve NAO pattern. All very uncertain but what can be extrapolated for next week is the chance of a mild SW'ly looks unlikely and with a greater chance of further settled and chilly weather. The 00Z EC solution for now though should not be trusted. Cheers. Matt.
  49. 44 likes
    The cluster 1 of n=27 (bear in mind there's inevitably individual variance between representative members in each cluster) has low heights to our NNW between UK and Iceland; +ve GPH/MSLP to our NW/Greenland and another focus to our NE/Scandinavia, ie effectively as an omega with mean NW-W flow. It's blocked, just not blocked in same guise as per cluster 2 (n=)24, which also has the strong +ve GPH anomaly to NW but also across Iceland, with Scandinavian trough/low pressure to our E and a mean flow from N-NE/E. Of course, the individual clusters contain members with flow between these main signals (virtually every compass point is signalled to some degree by 28th, with T2 spread suddenly more marked then, despite majority below avg) but on the lead-up through period 23rd to 27th, it's noteworthy how most members fall into a broad flow between N to NE. We shall see. EDIT: ENS plumes of both EC Op and new EC version still agree on marked spread developing Sunday 20th onwards. Watch this saga run and run.... ;-)
  50. 44 likes
    At present there's really little change to the dichotomy that has prevailed for a few days now and if anything, the 00z runs have exacerbated the uncertainty more (versus some continuity that seemed to be appearing prior). This weekend remains the 'fork in the road' of the medium range dichotomy: will NW Europe remain under blocked and generally colder conditions moving ahead, or will we move to a somewhat more progressive story of ridge-trough-ridge etc into the 15d period, bringing an oscillation from mild phases to colder and so-on? What *does* have higher confidence, in broadscale terms, is the clear tendency towards a very convoluted upper pattern hemispherically, making it prone to amplification and blocking. With -ve AO/NAO the preferred outcome on into December (and GloSea5 repeatedly and unwaveringly going for broad +ve MSLP anomalies across the UK into turn of month and a wholly blocked pattern into early Dec), there will come a tipping-point where we see better continuity in ensembles, but we're certainly not seeing that with any great faith....yet.
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