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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. 101 likes
    Righty-Ho. This can't pass without comment. Below follow just a random snapshot of detailed medium range briefings from Ops Centre made in first days of Jan, looking towards what was then the 10-15d trend (and now current-short term) period. I will leave it to others to judge if my UKMO colleagues have got things "so massively wrong".... Written 1 Jan: "The unsettled conditions continue into the trend period but with some evidence of increased meridionality in the upper pattern and so allowing for some greater space between systems and perhaps increased signal for some clearer/colder/showery conditions between." Written 3 Jan: "Latest f/c output continues to indicate a continuation of the predominantly mobile, and often unsettled, theme, with periods of wet and windy weather interspersed with clearer/colder weather. Some EPS members continue to indicate the risk of very deep areas of low pressure crossing over or close to the UK at times, bringing the risk of locally storm-force winds mainly, but not exclusively to N’ern areas. A few of the more S’ly tracks (currently about 10% of members take lows across Wales and England) would allow the entrainment of colder air into these systems, with a lower risk of heavy snow developing. All output does allow for transient ridges, but the wavelength of the upper pattern is such that any drier/colder interludes would be short-lived, and there is no strong signal for any prolonged settled spells, or easing of zonality..." Written 6 Jan: "The zonal, cyclonically biased spell looks set to continue for the majority of this period. Further very deep areas of low pressure are signalled to cross the UK at times, bringing the risk of disruptive weather with them, these in turn being driven by a powerful cross-Atlantic jet. Colder Pm airmasses (originally Pc airmasses with origins from N’ern Canada, though heavily modified) are likely to cross many parts between systems, bringing below normal temperatures, and a risk of snow/frost." Need I go on?
  3. 96 likes
    The current UKMO view is for a colder set-up to dominate again into the 10-15d trend period, with more progressive solutions in a minority. Possible net result is UK on western bounds of blocking with 'battleground' style issues in west thanks to periodic Atlantic incursions. Latest EC32 from yesterday is an interesting one; it also indicates a signal by Christmas for negative temp anomalies & HP to N; LP to S/SW, but the clusters do show a wide raft of potential outcomes. Anyway, very early days but tentative signs for something more blocked a bit further down the December diary.
  4. 92 likes
    For the newbies - a note a caution that alongside variance in the timing and scope of onset of any colder easterly feed, much as the models currently portray, don;t take the cessation (e.g. as per 12z GFS) too literally either. History shows us that once established, such cold takes some shifting and inevitably, the models exhibit set tendency to sweep the blocking aside and take us back to mobility. Thus, whilst we are still at tentative stages re onset (and any initial consequences, e.g., snow perhaps from Midlands northwards early next week, as the system from west Sun-Mon quickly occludes-out), we are most certainly nowhere close to estimating wht on earth happens thereafter. So, please don't take the model 'closure' of the blocked signal for granted.... we've been round this circuit before in recent winters!
  5. 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
  6. 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
  7. 82 likes
    I'm fairly certain when Frosty see's this chart: He's going to be outside doing a lot of this:
  8. 77 likes
    Sadly Knocker hasn't been bias corrected...........
  9. 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...
  10. 73 likes
    Or perhaps it means instead that some 'apparent' absentees are sitting back and looking at a very much bigger picture than simply building cyber snowmen to get knocked down, re-built, and then knocked down again in their back gardens on a never ending roundabout of neurotic armchair frame by frame dissection of intra 4 X day/night NWP output? Vicissitude revisited yet again. Most familiar. Interminable detailed analysis pouring over every chart within the context of what is a chaotic, messy cold trough disruption pattern - that has continuously moving marginal boundaries, from one locality to another, from one day to the next, and from this weekend and through much of next week, is completely and utterly pointless and has no reward other than perfectly avoidable mental exhaustion. Equally, posting selective mean charts from hand picked model charts within the context of what is evolving, totally skews and dilutes out what is going on right now within the NH pattern. For the first time this season we are looking at a progressive stagnant cold pool of air over Europe and the UK and a consistent trend to keep trough disruption into the continental heartlands. Troughs heading SE into this cold air mean snowfalls cropping up here, there, and everywhere. These cannot be forecasted most accurately till at least 24 hours before. Sometimes the biggest surprises and changes occur at t0 - t6. I believe that many will see these surprises in the day to come. Best wait till something falls out the sky first is my advice rather than building virtual hide and seek snowmen that are often days away. The macro pattern is changing quite radically from what we have seen so far this winter For the first time this season, heights to the NE stand a reasonable chance of becoming a greater influence. Whatever happens ultimately, talk of deceased easterlies is premature. For detailed reasons I gave yesterday, do not make assumptions based on any face value suggestions of a return to a sustained flat westerly pattern. The italics are most relevant. The foolhardiness of irrational and futile reactions every six hours or so is as poignant right now as it usually is anyway, whatever the prospective weather type. If this absurd dysfunction can't be self controlled, best to find something in the real world of greater importance that justifies worrying about
  11. 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!)
  12. 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
  13. 69 likes
    The final whites of the eyes of the resurgent vortex are now fully in focus of NWP modelling, ahead of eventual programmed momentum transport from Greenland to Siberia after this inauspicious end period of January to start of February timeframe. Indian Ocean tropical signal is creating another 'noise response', such as it did in December ,over the well fused together ocean/atmosphere Nino base state. The reduced tendency in atmospheric angular momentum from the heady values of recently is temporarily scrubbing some of the massive surfeit of westerly wind anomalies across the Pacific and creating a very pseudo and transient Nina-like synoptic response. Despite total budget AAM remaining high Only a very minor subtle shift of jet energy northwards across the US, but magnified greater by the interim strong vortex across Greenland to provide the very uninspiring flat westerly pattern downstream across the Atlantic of the next 10 days or so. As amplification starts to occur upstream in the Pacific, the net longwave tendency downstream is to retract the heights to our south and over Europe westwards into the Atlantic, and, with recent negative tendency in frictional torques as a manifestation of suppression of relative AAM tendency, this has the effect of beefing up the Azores High. This process is now well advertised in the 8 to 10 day modelling period. Frictional torques have now bottomed out, and starting to trend up in recognition of the continuing low frequency Nino signal in the Pacific. This sets the floor limit for relative angular momentum before rising once again At the same time, the MJO is set to continue its eastwards movement through the Maritimes and then onwards to the Pacific during the course of the first half of February . We should be mindful that modelling of this activity beyond a few days will be unreliable, and likely in that respect that progress will be underestimated. This is especially as MJO related activity is usually increasingly active approaching the later winter and then early Spring periods. With displacement and considerable perturbment likely of the stratospheric vortex during the very first part of February, and another round of soaring angular momentum as the MJO arrives at Phases 5 and 6, with the tropical signal increasingly gaining amplitude, then increasing eastward and northward progress of poleward rossby wave activity arrives in the Atlantic as the signal engages the Pacific as it did during this month and associated cold spell. Nino Region 1.2 (eastern region) continues to cool and assist the evolvement of a traditional later winter Nino cold pattern. With the vortex paying a price for its unwelcome re-staged party gate-crash of our winter, the scene is set for an increasingly amplified Atlantic profile leading to greater and greater blocking potential particularly later in the month. Both the long-wave pattern and Nino forcing look much better accorded to stronger and more defined heights over the NE Atlantic, southern Greenland and Iceland as the month progresses. Better than those seen this month, and with a stronger and more east based NAO profile It looks good for steadily increasing polar vectors through NW, N and NE through the progress of the month - beginning with polar maritime incursions in the earliest part of the month and becoming progressively colder from there
  14. 68 likes
    Leaked express headline for tomorrow. #sorrynotsorry
  15. 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
  16. 66 likes
    ... and there's a very good reason why they'll not get drawn too hastily in making pronouncements based on speculative or non-consensual modelling: because they are the de facto underpinning of UK-PWS weather warnings etc., and moreover are more than aware of the public 'fatigue' with seeing supposed 'snowmageddon/arctic blast/Siberian whiteout' hyperbole peddled to a largely non-specialist population by certain newspapers. This distinction between scaring the horses through the voodoo of Maddenology, versus measured, timely use of *Meteorology* and expressions of confidence (something you won't ever see expressed in newspaper articles: they are always 'certain' of the scary outcome), is key here. Equally, the 6-15/6-30d web forecasts are not created or written with enthusiasts etc in mind: they are there for Jo Public to comprehend and for that reason, you won't see talk of 'northern blocking' or 'Spanish Plumes' or whatever mechanisms. It's a poisoned chalice (as I've often said) writing these outlooks: rest assured most bench forecasters would far rather stick to preparing the 1-5d period narrative, rather than try to offer a reasoned explanation a fortnight or more ahead, strewn with model caveats and divergences way beyond the comprehension of most people reading it and thus rarely expressed in any detail. As for the period ahead, the UKMO assessment - as it stands - looks just fine: a broadly westerly-dominated story punctuated by threat of colder phases. The JMA solution is, be assured, one of many possible outcomes keenly watched at Ops Centre in so far as the 'colder phases' might be manifested. It might be instructive if the JMA solution is cited at all when their internal 6-15d assessment, based on 12z output, is circulated to us later tonight.
  17. 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....
  18. 64 likes
  19. 63 likes
    Ah those were the days, 'real' snow depths not your 1-3 cm and traffic chaos like now!
  20. 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.
  21. 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....
  22. 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.
  23. 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)
  24. 61 likes
    Merry Christmas to all here in the MOD. Even them who never contribute but eagerly follow.. Have a wonderful day
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    Loosely model-related - I suppose - but I thought I'd share with you all that I was talking to a colleague a few weeks ago about, amongst others things (like the mid-seasonal prognosis) rather bland stuff like NWP model performance. That, in part, came from discussion around what the likely improvements would be when GFS receives its major overhaul in April 2014. For quite some time, it is acknowledged that the performance of the GFS has been - relatively speaking - disappointing, and there's been a lot of discussions around why - for instance - verification is consistently behind, primarily, the ECMWF suite. I wasn't aware until recently, but but an experiment was carried out not too long ago into why this under-performance was evident. It is worth noting that NOAA attribute a great level of professional respect to their peers at ECMWF, and so enlisted their help to review and breakdown GFS. What was found was extremely interesting. The model itself, ie: GFS and its ensemble compatriot, GEFS, behave in very similar ways to that of the ECMWF model. So, in that case, why do they differ? Well, interestingly, it all depends on the initialisation data - and not so much on the algorithms. How was this proven? Well, in very basic terms, ECMWF masked across a set of their initialisation data - so that it would fit with the GFS criteria - and waited to see what would happen to the output. Unexpectedly, the verification of the output was consistently almost 10% higher than the GFS running average. In short, it proved that the performance of GFS isn't so much about the model in terms of mathematics or its physics, but more the depth and variety of the data which is currently being applied to it. It will be interesting to see how the 'new GFS' operates in the Spring. It will enact considerable upgrade to the definition and layering within the current model. It's taken them 18 mths to synchronise initialisation of the 'new' model with the 'old' one, but as far as I'm aware, they both run completely in parallel now. This is ahead of the NOAA's complete refresh of their supercomputing capability in 2015, which I hear will break new ground, with some talk about harnessing the cloud; pooled computing, that sort of thing. I'm sure more will leak out through 2014, so keep your eyes peeled. Finally, I would like to wish a very Happy New Year to you all! I do hope that, while extreme weather brings interest to us all, that we are saved the disastrous effects that we've all witnessed especially over the last couple of months. And with that, it's time for a drink (...or two, possibly three) SB
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    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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    Lol! Yes and I now have the waistline that I didn't envisage a few years back, very little will power and too much nice food! I have in the past posted some nice pics of the Pyrenees from my terrace but in view of the UK snow drought I didn't want to add insult to injury this winter! Yes its strange that I'm more interested in your weather than mine. I'm more chilled out about the weather down here as long as its cold enough for mountain snow. But bear in mind I did suffer decades of frustration in the UK as a snow lover so am always happy to see some good wintry synoptics for the UK. These are a couple of pics to give you an idea of why I came down here: I always say to friends that they must come down in the winter because although the mountains are nice in the summer theres something really magical about them in the winter.
  30. 57 likes
    With the polar vortex weakened natural state as it is this winter, we don't actually require an SSW this season. In many ways it might actually be preferable we didn't actually - but that is for another time and place and not this thread. One thing that can be said with absolute certainty is that it is far far too premature to declare that last sentence. No-one can deny that expected, and very well reasoned, evolution to a dominant -AO pattern has been put back. But then again it was being viewed at the outset from an accelerated track - faster than some of the coldest winters ultimately have delivered- and herein lies the perspective we should currently take with the outlook into the New Year. Which clearly means that there is a lot of winter to get through yet But back to the beginning : Customary lack of apology extended here for snippets from a previous update a few days back as a usual attempt to try to provide continuity and progress..and most of all perhaps for purposes of this thread, some perspective. I think we need to remind ourselves where we stood earlier this week. A lot to take in since then --------------------------------------------------------------------------------------------- <There is no surprise at all to see indeterminate suggestions from G5 and ECM ensemble data for the further outlook from Christmas itself and beyond New Year < a panacea of solutions appear in the modelling.... including cold pattern solutions. <This suggested upstream change, courtesy of continued modelling of GWO heading to phases 1 and 2 in conjunction with falling AAM is well advertised now across the modelling. <The turn of the year and early part of 2015 is going to be very tricky to predict I think, and we should be prepared for quite possible sudden and significant changes of travel for that trend period in the lead up to Christmas. Slower flow leaves room for better jet amplification. However, taking into account present conditions over the polar field with zonal winds only just set to start falling once again over this period in response to fresh wave activity on the vortex, then calculating amplification equations is going to be difficult. Much easier for the models to handle much more predictable faster zonal flow. If WAF really ramps up, as it may well do in the days to come - then the calculations will increasingly become more and more in our favour and the type of alluring GFS output we are currently seeing in FI may become more and more plausible sooner rather than later. Caution advises, as reasoned later in this post, that it might be a little premature at this time - but all bets are off as stated in the extended period. < the EPO ridge heading into the pole over forecast period will prompt further attacks on the vortex. With that in mind, and with the polar profile improving once more after the recent lull - as zonal winds slow more and more over the remainder of December courtesy of the resumed wave activity on the vortex - could it be that the amplification signal being picked up in the last week of this month leads us to simultaneous timing of vortex demise and flip in the NAO from the persistently + signal we have been seeing... early in January? There are dominoes to fall that need a little luck (for coldest outcomes) Hopefully the troposphere/stratosphere relationship (allied with the atmosphere calling in a favour for us) will do the rest.... Edited by Tamara תָּמָר, 16 December 2014 - 19:05 -----------------------------------------------------------------------------------------------. And so it is proving very tricky, and even more complex to see the way forward than could have been anticipated The greatest uncertainties of all lie in the upcoming tropospheric/stratospheric direction of travel. Much hinges on these developments to take advantage of what could be a big opportunity to flip the pattern properly colder in the shorter/medium term. Much as has been written about in detail in recent times. There continues to be a further possible bite at the cherry upstream for atlantic amplification potential and there is still ensemble support for this to happen this morning. It is not time to throw in the towel on the Christmas/New Year week just yet. This further amplification in turn would provide the wave 2 activity that would be the catalyst to undermine further a very weak and vulnerable vortex and which would get us to a more sustainable cold pattern relatively quickly. Much as highlighted a few times previously . The GWO is fast orbiting Phase 1, and Phase 2 (atlantic amplification phase) is proving too much of a 'pit-stop' first time around. This is behind the current erratic chopping and changing and apparent frustrating atlantic pattern phasing through the festive week The sequence upstream ( underlined by -AAM tendency which on its own makes model tracking harder anyway) is accordingly fast moving, and is set to be punctuated by a brief poleward westerly burst (30N). This is behind some of the flatter modelled scenarios cropping up in the modelling. No surprise in the absence, yet, of zonal winds across the polar field being reduced sufficiently, to see the modelled mid latitude ridge response over Christmas itself and hence the more flattened first attempted atlantic amplification than seemed apparent a day or two back. The knock-on effect of this is that we require greater things from any second round of amplification - which is the gist of what bluearmy has said this morning   GWO forecasts over the next day or two will continue to give us a guide as to where models take their cue regarding further attempted amplification. There remains guidance this morning for rebound to Phase 2 from 3/4 and this supports NOAA guidance for ensemble amplification support . The degree of amplification upstream after Christmas will determine the aforementioned wave 2 activity on the vortex that in turn is required to get us to any immediate longer term cold pattern ( if it is going to happen) faster. In the absence of this (or it being too insufficient) the reset pattern, (much under discussion already elsewhere in reaction to the latest Cohen blog) is the slower train to cold coming from the east - and that prospect is clearly going to prove quite unacceptable in this thread!! But here we should remind ourselves that we don't need an SSW to get us a sustained cold spell. December/Jan and Dec 10 are very good recent examples Plenty of very good information has been written by members in the strat thread in the last day or two indicating possible split vortex potential courtesy of this wave activity around day 10. Lets hope that these signals verify into something concrete - the coming few days will tell us more about this though and best to avoid pre-emptive assumptions in the meantime Uncertainty can be a good thing as well as bad - and in the face of such outlined complexity then best to make no predictions and see what the coming days brings as further changes are likely to come Frustrating at the moment I understand it may be, but lets please at least hold off indirect winter obituaries via direct LRF obituaries. We can only reason the way ahead but ultimately, no-one, not even the professionals in the METO and elsewhere, can control and 100% predict the weather. There is far too much short term knee-jerk reaction in this thread each day as it is, without terminal seasonal knee-jerk on top of this..      
  31. 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.
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    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.....
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    Well well well this morning feels like we have rolled double 6, landed a royal flush and spun green 0 on roulette all at once, No fancy analysis required no detailed confidence posts just happy that all the main 3 are identical st 72,96,120 and 144 with wiggle room for upgrades and potential for snow as early as late sunday.... ECM 168 has widespread -10 air & -12 just coming across the north sea The same north sea thats warmer than usual....... Have a good day S
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    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!
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    ...and by 29th, 27 members have us in a chilly cyclonic NW-Wly; 24 in blocked, cold N-NE'ly.
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    You may have noticed some acronyms are have started being underlined this pm - this isn't an advert that'll popout like some sites have on this sort of thing, so don't panic - it's an acronym expander so if you're wondering what things like NAO or UKMO are - mouse over them to get the full meaning.
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    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.
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    So then, we arrive somewhat disjointed at a potent cold snap.- which has the potential to last 8 days ( day 1 is T48) - possibly longer. Since March 2013 there haven't been ANY HLB synoptics, with just very short NW transitional Pm flows last winter. - so of course we can all understand the desire for our own 'imby' to come up trumps in next weeks scrum of low pressure drifting / sliding SE. My thoughts thus far is that as we home in on the slider low the track & intensity probability wise do NOT favour snow for the following areas. SW - South of M4, southern England- again along the south coast & the shires more so & also the SE corner like Kent & Essex / sussex. ( if the PPN makes it at all) Why? If we look at the information available from UKMO & ECM we see the tracks: ECM- 120- http://www.meteociel.fr/modeles/ecmwf/runs/2015011412/ECU1-120.GIF?14-0 144- http://www.meteociel.fr/modeles/ecmwf/runs/2015011412/ECU1-144.GIF?14-0 The ECM tracks the low across Ireland towards wales & then into the channel & deepens it to 976MB, which is far to deep for a slider. This sort of depth - creates turbulence & forces milder TM saturated air ahead of the system, because of the turbulence the slightly milder uppers & indeed a increased 'melt layer' in the column of air from cloud base to ground mix ahead of thee frontal zone NE wards- so your surface cold is all gone by the time the PPN arrives. remember 'Deeper the low = further NE milder penetration', so along the lows track you would need to get into the midlands to find the snow line. UKMO is better because the intensity is shallow- which is likely to be the form horse- However the track is flatter & less acute. 120- http://www.meteociel.fr/ukmo/run/U120-21UK.GIF?14-18 144 http://www.meteociel.fr/ukmo/run/U144-21UK.GIF?14-18 Track is through Ireland across the central belt, meaning again you can forget snow for the south, its reserved for the North along the line where those tight easterly isobars are. So of the Euros overall neither paint a great signal for the UK, however the ECM does look good for snow further North. Whats going to change? well the optimum for retaining snow prospects was the NAVGEM http://modeles.meteociel.fr/modeles/navgem/runs/2015011412/navgem-0-132.png?14-17 low mixing from the warmer air & a very shallow system. So as it stands based on a blend of ALL tracks & intensity + the fact there's no HLB directly to the east enforcing a deep SE flow out of the continent theres is MINIMAL slider snow prospects for the SE / SW / South- but please reflect on the high uncertainty allowing for some adjustments that could suit these areas ( the most likely adjustment is the PPN doesn't even reach these SE / E areas. ) Once again areas in the firing line seem to be the central / North midlands & areas possibly further North which if you catch the slider right, will see continuous snowfall as PPN arrives then slides east & stalls before pulling away south. Prior to the slider, A potent storm- followed by Squally Wintry showers in the NW when eventually becomes Northerly - As the wind swings closer & closer to the North so this flow becomes very cold & associated dew-points will drop out sub zero. I have highlighted an embedded trough swinging SSE through the UK on Sunday, however again the south & SE may not have sufficient depth to the cold ahead of it at that point to support snow. - so what appears as snow in the midlands may end up a sleety mess in the E/SE corner. Post the slider event may well be the chance the NE/E & SE have been looking for with a backing west of continental cold, this all depends on the ridging NE of the altantic high cutting off the trough feeding the sliders from SE Greenland. The immediate upper air profiles to the east wont be 'that' cold so 24 hours of flow at least will be required before any deep cold may arrive. ( triggering convection ) What's not been mentioned to much thus far is the potential for a very low CET period spanning 7 days for Scotland & the North. The central belt of Scotland could see overnight lows approaching the magical -15c & with that depth of cold the recovery across the snowfields may only see maxima -5cs returned. - so low single digits of negative CET could be the order of the day. Frozen rivers & lakes etc could be common place by next weekend. In summary then a bit of a messy pattern, - Messy usually means lots of snow & if I was located in the central / northern belt as it stands I would be satisfied that I have the highest probability of frontal snow. For the snow starved elsewheres in the south its a case of wait & see with baiting breath but as it stands the initial set up & prognosis doesn't look 'that great' regards S
  39. 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...
  40. 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..
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    Once again, Euro trough omnipresent. Once we get cold, the permutations are all loaded towards the cold variants.
  42. 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.
  43. 51 likes
    Remarkable outputs for cold especially given the lateness of the season.It just shows with the right pattern would can be achieved even in March. Both GFS/UKMO charts show the unusual depth of cold engulfing the UK by Monday-day 3 now! UK charts here for t72hrs you could not have a better angled feed from Arctic Siberia than that.Perfect alignment south west into W.Europe and the UK with -16C uppers already touching Kent with that large area of cold pooling waiting to come in through Tuesday/Wednesday. Look at T120hrs and the expected strength of that easterly across us That wind chill will be severe and biting,add in the now probable snow bands for many areas through the week because of the deep convection then what an astounding period we are in for by the looks of it. I have seen all the severe spells since 62/3 and this as it looks now will equal and possibly exceed many of them for severity even if not longevity. Winter model watching doesn't get better than this!
  44. 51 likes
    I don't like all these personal digs creeping in again tonight, I was one of the victims last night for being positive / optimistic and I still think we could get something out of this but let's show respect to others opinions even if you strongly disagree and don't let it spoil Christmas.
  45. 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
  46. 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?
  47. 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.
  48. 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!
  49. 50 likes
    Afternoon All- So im logging off for Winter...- Have a great year- see everyone in October- what a crap winter its been. This week we could see an 18c in the SE- enjoy the warmth!!!!!!!!!! S
  50. 50 likes
    Actually as of last night, 50% of MOGREPS members heralded an easterly by next Fri and that suite is currently exhibiting near record high levels of Shannon entropy out through day 10 onward. Given some support (albeit still minority) in EC ENS for cut-off low to SE and easterly feed, UKMO urging caution on being too prescriptive end of next week onwards, despite majority westerly solutions. In short: nothing yet discounted.
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