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  1. 114 points
    Evening All Ice Cold hope your still with us .... So the much touted SSW is coming into view & here’s my thoughts + timelines of when / where to expect it... We have seen lots of posts & comments on it - but whats the reality likely to be -??? The Omni present warming in the GFS charts is usually due to the model & its poorer vertical resolution V the ECM, as a result there is an over reaction / over estimation of how much a warming is going to impact the zonal wind @10MB - so because of this 'bias' when viewing the mid / long term outputs churned out by the GFS we have to be a little on the sceptical side as these are normally moderated & scaled down even wiped out ! However we have now seen the evidence in the Berlin site that a downwelling SSW event will make it to the 10MB level & indeed go on to challenge the date record for the time lf year- ( this is NOT the same as the usual deceleration of the zonal wind we see at this time of year as that is more of a gentle reduction all the way to mid april when the vortex breaks its annual westerly influence ) So as highlighted we have passed the point of no return in the stratospheric modelling where a SSW is now just 5 days away for the 12th Feb *** Take note of this date -- The plots below show steep downward curve of a signature warming Note the main black line being Climo - but the ensemble mean from the GFS running out at mid -20 to -30 M/S... The clustering is quite close - further backed up by the another illustration of the ensembles from the hannah attard site With the mean bottoming out at -32M/S *The date record for this time is ~ -17 M/S & the all time record low ( using Merra data ) is -35 M/S The ECM berlin forecast below is not as bullish as the GFS coming out around -17 M/S @10MB but none the less still classed as significant event... So what we have in modelling terms of a SSW due is * The first one in 9 years ( I dont think last year was classed without checking ) * Possible record breaking reversal of tge zonal wind... If your thinking whats best in terms of impacting the UK its simple- The lower the negative number the better... - record breaker ? yeah I will take that please... Why?... The bigger the negative number the stronger the easterly flow is across the mid lattitudes. !! ( think feb 63 / jan 85 & so on ) Whats the models churning out then? The SSWs are classed as 2 types - Wave 1 displaced vortex or - Wave 2 Split Vortex .. This is whats expected - A classic wave 2 Split vortex- with 2 clear areas of poleward flux - over the far East & canada- Now luckily for me the historic SSWs have already been classified -we are looking for la nina years / W2 / split vortex- 6 years appear as matches - 28 Jan 1963 - 7 Jan 1968 - 18 Jan 1971 - 1 Jan 1985 - 21 Feb 1989 - 24 Jan 2009 Below are the 10MB increase in temps at the time when the zonal wind hits 0M/S Obviously they all have 1 thing in common- The huge rise in temps across the pole - Now the Date of the zonal Mean hitting 0M/S isnt the day of peak blocking - Looking at the dates above peak blocking appeared 7 - 11 days post Reversal - see below day 11 charts from the above warmings ( 500 MB anomaly ) Whats apparent is HLB is quite prevelent & most are centered ( for us ) around greenland & Western Scandi - Also all 6 Splits have varying levels of troughing to the south - but all have an anomaly- So that really leaves with a level of expectation that should at least give us some confidence for Feb over the following dates- 12 Febuary : is 'R' Day- as in the reversal of the 10MB zonal wind where the eastward progessional component is replaced by a westward one 13/14 Febuary : is peak 'R' days where we will know the magnitude of the warming & just how much westward ( reversal ) component there is - Sub -20 M/S is the date records & anything below is the jackpot - 16-18 Febuary - Mid to high lattitude transitioning - This is where depending on how lucky we are for our area we will see MLBs start migrating North to the pole as zonal wind lag filters through the lower layers of the atmosphere & support builds for HLB - look for the 3 key wave patterns ( atlantic / Scandi & pacific (-EPO) The UK can get very cold in this period if the migrating highs are favourably positioned from the outset.... 20-24 Feb - Peak HLB blocking across the NH - peak -AO signature & peak cold overall for the mid lattitudes ... *** IF the GFS lands with the depth of negativity then Late Feb early march will be on a par with 2013 for AO negativity & possible / probable UK cold / snow.... if the negativity is watered down then the cold signature will be watered down & less dominent in western Europe... Best S
  2. 90 points
    Microscale detail absorbing an awful lot of attention on here, when in reality it is a waste of emotion. The macroscale pattern is now fixed - it will not change significantly now for the start of next week, and while we can hopecast for a front/kink/trough to appear in exactly the right place for every IMBY desire it is frankly impossible at 7 days' range. We wouldnt even try to get that right on a standard westerly atlantic pattern - how can we hope to get close to specifics 5 - 10 days out from the main event when we are seeing dramatic events unfold in the strat? Remember - we are still in reversal for several days yet, and the models will have larger than usual error bars on microscale events. We couldnt hope for a better anomaly chart to see in the new month and this is a belter from GEFS to kick off the week on Monday And the strat? By day 10 it has reformed over the pole as the reversal ends, but the shattered remains at 10hpa are weak, and a large eurasian block is still in place while zonal wind profiles recover to weak levels over the pole, but see a very muddled profile at 55/65N suggesting anything but a recovery. Sustained chance for high lat blocks to survive in situ though the storm track will gently slide back north. Battleground snow? Down at 150hpa blocking clearly still in place over Greenland So - 10 days of almost zero chance of a substantial change to the pattern, and decent confidence in any recovery from this point being slow and painful for the vortex. Next week will be very cold as we know...and the week after will also be cold, quite possibly for all parts throughout the week. Confidence then less sure by week 3 - need to see how pacific forcing may impact at that point, and just how quickly (if at all) the vortex recovers. If it is too late for a recovery then kiss goodbye any early spring as cold will continue to spill out at times right through the month in all probability. And what about snow next week? Well - I think all this hand wringing over each individual model is a waste of energy.... but maybe history can help. 3 days before we were hit by substantial snow in 1991 the charts looked like this 3 days before the snow hit in 1987 We are forecast currently to look like this in 72 hours BUT we know we have an SSW in the bag and a signal for sustained blocking and a retrograde pattern Which would you rather have?? Both 1991 and 1987 delivered plenty of snow. What do you think is likely from here if they are analogues to go by in terms of snow fall... - and what about the signals for longevity listed at the top of this rather long post?? The only thing going against us this time is the calendar date. All very very good. People criticising this setup really and truly need to get their history goggles on and then wander off to a quiet corner, tail between legs.
  3. 85 points
    I think too many have already become desensitised to what constitutes a 'fantastic chart' and the seasonal ailment of this thread (which is irrationally mood driven anyway by the more average synoptic charts that are customarily on offer) has taken on a latest variant of becoming superimposed and twisted on the absurd semantic that 'merely' only UK Tundra conditions are being shown and not the Canadian variety. Truly, if you cannot exercise self control in front of your lap-top by the smorgasbord of dessicating cold solutions evident on NWP, especially as we are heading right into meteorological Spring, then its maybe best that a different form of self torture is considered to spare those who take a more considered perspective. This has nothing to do with any regional bias (coming from a part of the country that relies on these increasingly rare sort of synoptic to get a snow fix) its to do with the usual fascination I have for sitting back and marvelling at watching a pattern like this unfold in the greater macro scale. If/when it snows at home, I will be less inclined to spend spare time waiting for when it is next going to snow, or when its going to end - but instead getting out, having fresh air, exercise and enjoying it. And then, when the snow and ice is over, it will be a case of seeing how the patterns evolve through Spring and into Summer - looking for the best that can be on offer for this Island, whose micro climate is fickle, elusive and overly too mobile to the sort of sustained blocked patterns that can be the deeply cold derivative as upcoming next week, or depictive of deep Azure blue skies, sunshine and warmth of the summer. Get used to this reality - it will always be thus
  4. 80 points
    Well it's probably fair to say that I've been rather quiet on these forums for the last few years really, especially since 2013. After 15 years of internet weather watching, and more importantly, having witnessed the incredible run of winters we had from 2009-2013 (vs the more Ian Brown style winter in the preceding 10 years), it really takes something now to get me to show more than a fleeting interest in what's on offer. Now it's safe to say, regardless of geographical bias (bearing in mind I now work in Central London and live on the SE'ern edges of our ever-warmer capital, so I am pretty neutral when I say this) this winter has, thus far, been the most productive for watchers of a colder persuasion since March 2013, with many parts of the country seeing at least a covering and some lucky folks through Central England seeing 3 pretty decent, if temporary, snow events (of course those further North and more vertical than the rest of us have seen far in excess of this, but those lucky b******s get to see this most years). But what we stand on the cusp of, what is being modelled within a pretty reliable timeframe, is reminiscent of those days back at the beginning of this decade where the sun went to sleep and cold chaos ensued. It is far to say that, beyond just the pure pornographic synoptics, the likes of which we had not seen for many years previous, 2010 ruined the laws of model watching in so many ways. Forecast models are not supposed to pick out the correct pattern at +360 and run with them pretty much right through to +0. They're supposed to tease us with big greeny highs, fallible dreams of the biggest snowstorms of the last 100 years (circa December 2012) and then leave us distraught, crying in the corner of the shower, attacking the 'mildies' on here with our not-quite-waterproof smartphones (what a long way we have come...) at even the merest hint of an 'I told you so'. And I genuinely think the 2010 episode of near flawless modelling has left a lot of people on here far too expectant of the capabilities of predicting the friggin future with a lot of electronic circuitry and fans. This is why, more so than at any time in the past 5 or so years, this current phase of modelling really has my interest. We are on the cusp of something which, pre the 2009-2013 phase, would have had me online from 8am-10pm (which, if memory serves, is when the old BBC slowwatch forums used to shut for the night) in a far too nerdy way (nobody ever understands our snow obsession right?). Some members on here can be accused of being just that little bit too optimistic when it comes to cold and snow chances, but those same people are very much correct in these sort of short-range cold shock scenarios - whilst the models might not yet show anything significant snowfall wise, they never do until much closer to the time. In fact, if we think of events such as Jan 2003, Jan 2004, Feb 2005, Feb 2009, Jan 2010 and even in to Feb 2012, Jan & March 2013, all of them had modelling which at face value painted a cold and dry scenario....which continued until a few days before unexpected features popped up in an increasingly unstable flow given a significantly lower than usual upper temperature profile. When you combine that with the anomalously warm seas surrounding the UK right now, there is an inevitability about unexpected short range snow events. Beyond just next week, we also have a pretty consistently modelled significant warming into the stratosphere, which should yield an interesting second half of February, combined (or perhaps even coupled?) with one of the most significant MJO episodes we have seen to leave us on the cusp of a pretty memorable February overall...now when have we seen that before, with a declining solar profile...memories of 2009. Enjoy the next few weeks everyone, I will certainly be more active on here as we stand on the edge of what, from 15 years of experience, feels like a pretty significant period of wintry weather for our humble little island.
  5. 79 points
    I wish you guys could see the precip charts on the EC. Serious disruption Tues and Wed on this run across swathes of the country.
  6. 79 points
    In days of old, When nights were cold, And models weren't invented, We might have hoped, we might have prayed, But we didn't drive ourselves demented. The MJO the QBO, No wonders such as these, All we had back then my dears, Was Uncle Bert's dodgy knees. He'd hobble along with back bent low, Telling all who passed 'it's goin ta snow' 'They're aching bad' he'd say, 'eee I wish I were fitter', 'You mark me words ma lass, tis goin to be bitter'. More often than not he was right, A deep white carpet fell through the night, We'd wake up to an eerie glow, First words of the day...'Yippee, SNOW!' Those days are gone, but not forgotten, Few snowy days now, seems so rotten, What will it take to make dreams come true? A long fetch beast, a bolt from the blue? A slumbering Sun? A boiling hot strat? A volcanic eruption? Dear God please, give us all that. When I was little, I'd be told, 'Yer won't like it so much when you're old' Mummy dear, I'm afraid it fell on deaf ears, I'm as bad as I was, so I'm here with the seers, I look at the charts with their purple and blue, It's all double dutch, I'm reliant on you, I've read and I've studied, I've tried and I've tried, Still makes no sense, my brain must be fried I understand there's lows and there's highs And a beast from the east makes white stuff fall from the skies But down here in the soggy south west I fear it will mean just slush at best I'm not giving up on those dreams from before, When I lived further North, instead of south of the M4, It must still be possible to get a battleground, Hopes of it happening are still around Down here we must settle for the dribs and the drabs, Seems snow is still out there, it's up for grabs, What must we do to get it to come here? Or do we just get to drown our sorrows with beer? The easterly beast that all winter's been bumbling, Will it get it together or carry on rumbling? How hard can it be to waft this way? All together now, let us pray. There'd be whoops of delight and cries full of cheer If we wake up one morning and find that it's here Open the curtains, let out a shout, 'See, I told you that's what the models were on about' Oh how I hope those dreams come true, But as I said, I'm reliant on you, Please be honest, please don't bicker, It makes reading these pages so much quicker. So finally before I go, To dream of the day we do get snow, To Paul and the Mods, be kind, please, Just lightening the mood of the FI tease.
  7. 77 points
    Another great day of model output with no concerns from me with what is shown. 2 points First is that the worst model output that we have seen today and the last few days is far better than the best output that we have seen for many a year. So don't be concerned with operational variations. The second is that normally any shortwaves scuppers any cold spell, but in this case I welcome shortwaves because once that cold air is embedded ( and movement will always be west of the general pattern), then we have shortwave snow making machines on our hands. The more shortwaves the better as far as I am concerned because the large Greenland block will keep us embedded in deep cold.... Just enjoy the output and whatever it brings.
  8. 75 points
    Well - ho hum - let's have a sit rep. My eyes are hanging out on stalks. The pacific first - engine of the climate system. How is our AAM looking in the face of the current high amplitude MJO? Tendency off the chart. How is our mountain torque input responding to the parallel rise in frictional torque? Off the chart. And the MJO itself? Well - not off the scale but not far off it. What does this mean? In a nutshell - strong pacific signal for high latitude blocking as AAM in northern latitudes falls and sub tropical high pressure gets the rug pulled out from underneath. Wouldnt it be great if this could happen in tandem with positive developments in the arctic stratosphere? Ummm - ok - funny that... 100% support now from the GEFS for a reversal at 10hpa 60N as a result of this: Huge burst of flux energy being punched straight into the vortex in the next week or so resulting in all the pandemonium on twitter today from the strat brigade. Flux angle is straight upwards - smashing into the poor vortex and giving it all kinds of grief End result: Vortex split in half in about a week's time just prior to the reversal. Proper SSW in sight - even the MetO have publicly advertised this today. What does this mean on the ground? Double whammy. Pacific forcing is pumping up high lat blocks - phase 7 composite for Scandy - while up above the vortex splits, slows, gets all in a muddle and ends up dropping one shard of the vortex over Russia and perhaps European Russia. End result - even stronger signal for the Scandy high that is already in place thanks to pacific forcing.... and a reversed flow via displaced vortex shard encouraging cold continental easterlies under the block. Length of spell hard to be precise... but certainly more than a few days. A double whammy like this would leave a strong blocked signal in place for more than a week at least - maybe longer depending on just how battered the vortex is and how quickly it could reform. Eyes still out on stalks. This is definitely a one in 10 year event - and actually it might be more than that. Cohen is advertising 1985 as the last time we had a vortex split like this one... and we ended up with this around 2 weeks later Response time for our current event looks likely to be less than 2 weeks - Chio reckons pretty instantaneous. So - are charts like this on GFS for the return to school after half term likely to come off? Yes they are. Potential is there for this to be one of our big periods of weather that gets marked in the history books. 81, 85, 87, 91, 96, 10 - and maybe now 18. Can it go wrong? Of course - as fast as it went right... but who gives a stuff about that right now. The dominoes are currently aligned... so no gloom required. And the dominoes are looking steady.... Funny. 10 days ago I was gloomily expecting the final pacific cycle of the season to be as tame as the last 2 and to give us at best a mid lat block in the face of unremarkable looking conditions. Omega block... bit of frosty gloom... the best of a poor season thought I. Strat forecasts looked moderate - no sign of a reversal if we are honest... MetO forecast nowhere near mentioning "very cold." And now we are looking at something potentially special (though note this is NOT a snow forecast because getting the cold in is only half the battle... the other half is getting the precipitation and that requires some luck.) Now... where's my hat and gloves? Not needed them in Somerset for a very long while.... tropical moths probably got 'em.
  9. 74 points
    I quite often agree with your sort of sentiment, as I'm one who opts to look at the most likely solution to fit the signals rather than the preferred one But, equally impartially and with intended objectivity (hopefully): The situation at present is a highly unusual one and the risk of some astonishing late season wintry weather is much higher than usual, certainly than often seen in these cases where deep cold pool advection flirting with the UK graces the perimeters of more 'reliable' NWP The repercussions of this SSW are going to be sustained. The clock starting ticking back in January and carried on through this month with extreme instability of the atmospheric profile with the tropics and extra tropics being subjected to opposing high amplitude states of angular momentum tendency. The impact on tropospheric global wind-flows (the Jetstream) has been significant, in addition to the detonation of some intense cold pooling over the polar field (relative to the modern day generally warmer arctic) : more especially across the Canadian arctic as multiple programmes of hot needles are probed into the polar stratosphere The result of extreme tropical momentum and stratospheric implosion implies high impact weather events on a broad-scale. Some places are going to get bitterly cold and some weirdly warm. In this day and age fewer parts of a hemisphere can get cold with less to go around than used to be the case maybe. But this programme of events strongly favours the European sector to become bitterly cold from what looks to be an impressively large breakaway cold pool for the time of year from Siberia. While its true that the envelope of this cold has boundaries that shift in intra suite modelling, the focus of the BI being impacted in inclusion, is much higher than other situations where lesser broad-scale drivers have been in evidence Ramping indeed requires a justification - I think this situation fits that criteria. Areas of land mass infrastructure most at risk aside from weather impacts (hopefully with least human welfare risk), the synoptic blocking pattern and its associated reverse polarity from one side of the Northern Hemisphere to the other - is not something seen on an every day NWP menu
  10. 73 points
    Cold - Yes Instability - Yes Prolonged - Yes I just wet myself - Yes!
  11. 73 points
    Right time to knock it on the head. I am not interested and neither are most of the posters on here interested in how climate change may or may not be influencing SSW impacts. Keep your bickering to the climate change forum and let us concentrate on whether or not we will have a productive easterly or not. Thnk you.
  12. 72 points
    netweather members celebrate when the long-awaited easterly finally arrives...
  13. 70 points
    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!)
  14. 70 points
    Sorry, I just thought I’d walked into the moans threa.. oh wait. <passes around a big bag of grips> No sooner do we get a cold spell within sight it astonishes me that time and time again some people seem hell bent on being the first to find signs of it unravelling. Is there some kind of prize for this I don’t know about? We don’t live in Siberia. We are never going to have three month of bitter cold. We all know this! It’s one run. 48 hours ago some of you were dismissing the idea of an easterly entirely based on the output. Maybe when the hangovers and cruddy moods have lifted this will improve the quality of posts?
  15. 70 points
    00z EC showing interesting battleground snow event for the north and west next Tuesday, as Atlantic frontal system moves in from the west and bumps into the cold air If only my wife could understand my fascination of looking at weather charts ...
  16. 69 points
    WHY I BELIEVE THAT THE GFS OUTPUT FOR WEEK 2 WAS COMPLETELY WRONG My post yesterday (now buried on page 2 of this thread) compared the run into to the predicted upcoming cold spell to some earlier severe spells dating back to 1947 and up to 2013. I will make further reference to the March 2013 spell towards the end of this post when I compare it to the current and predicted set up. I intend to demonstrate with plenty of evidence why I feel that the GFS is being far too progressive in bringing back the Atlantic after the turn of the month. In fact, I do not necessarily see this happening until well after mid-March, although one or two very brief less cold interludes can never be completely ruled out. This was based on the previous few runs up to today's 12z. I see that the 18z (which rolled out while I was writing up this post) has a slightly colder solution again but still ends with less cold uppers over the UK and is a long way from the 12z ECM and UKMO solutions.. CURRENT PATTERN AND CONDITIONS In summary, the record strength sudden stratospheric warming (SSW) has fully impacted and reversed the winds with the Arctic cold being displaced towards the middle latitudes. The jet stream has weakened and split and the Atlantic LP train has ground to a halt. The persistent and very strong Canadian PV is coming under attack and all models show it breaking up over the next few days with the main lobe transferring across the Arctic to Siberia during the next week of so. The blocking patterns are becoming established. During the next few days, the HP close to the UK is set to link up with a vast expanse of HP extending from northern Siberia through Russia and pushing westwards to Scandinavia and beyond. Once established, this is likely to dominate the pattern for many days if not weeks. The deep cold over north Asian and Siberia is surging westwards. I show the "current" charts below from the 12z run. I used the GEFS simply because it starts with T+0 (GFS operational run starts with T+6): Jet Stream Surface Pressure 850 Temps 2m Surface Temps Now, I'll go through this in a little more detail. I had a glance through the strat thread to get the latest on the SSW and I must thank @Blessed Weather for directing me to @chionomaniac's analysis of the significant second warming which has effectively to quote "knocked out the sister vortex over the Hudson Bay and will cause the NAO to go strongly negative". In simple terms this means that the Canadian lobe of the vortex will be more or less destroyed (as will be seen in the later charts below) and the remaining fragments are being pushed away across the Arctic. I have also seen the comments from a number of the strat specialists that the record strength SSW and the further warming will extend into the "final warming" which normally occurs as we move into Spring (in March/April but can be a few weeks earlier or later). This means that the PV will not reform until towards next winter. Assuming that this is correct (and I have absolutely no reason to doubt it) then the wind reversal will continue for an extended period and HLB patterns will be maintained for many weeks as reflected in a strongly negative AO (Arctic Oscillation) from later this week and the Atlantic will be blocked with LPs making little of no progress against the HP block and being forced much further south as reflected in the NAO (North Atlantic Oscillation) about to go strongly negative too. The current pressure chart shows that strong Canadian lobe right now. The jet stream is already starting to buckle, looping around the north of the building Atlantic HP. The stronger streak pushing out of North America is already bending southeastwards. There is a fairly strong southern arm pushing though North Africa and well south of the Mediterranean. This is already a classic set up with the jet pushing LPs well to the south and on a nice clean and direct route. This should prevent any chance of an LP stalling and moving up through France and introducing winds from a more southerly quarter. Meanwhile the Atlantic HP is ridging strongly right up into the high Arctic. This in turn links up to the belt of HP already established over north-east Russia and Siberia. This pattern is now primed to evolve into a much greater area of HP which will become dominant and control the weather patterns in northern Asia, Russia, Europe, the UK and well beyond (as described in the next section). I included the temperature charts for general reference but I will not comment on them. I will be producing one of my Eurasian temperature and snow cover reports tomorrow with current sea surface temps and dew points too. A WEEK FROM NOW: Now let's have a look at what the 12z model output is telling us for the end of week 1. To keep this as brief as possible, I'll only compare GFS and ECM output. I know that there has been some very good output (for coldies) from the very consistent UKMO (but that only goes to day 6) and GEM falls into the same bracket. These are the 12z T+168 charts: GFS: Jet Stream Surface Pressure 850 Temps 2m Surface Temps ECM: Surface Pressure 850 Temps Note how the jet stream profile has already changed completely. It has generally weakened and the northern arm is almost non existent. There is a small streak pushing south-westwards out of Scandinavian (part of the pattern reversal). All the energy is now in the southern arm which powers even further south through North Africa. There is a minor loop through France which is not entirely logical and may be part of the later GFS divergence later on (I'll return to this in a minute). GFS has completely smashed the Canadian PV lobe and it has been replaced by strong HP. The remains of the vortex are shifting across the North Pole on the way towards Siberia. The HP has built powerfully across form Siberia, through northern Scandinavia, onwards through Iceland and extending all the way into Greenland. The strong easterly has been established. Meanwhile, there is LP east of the Azores. There is also a small LP running south-westwards out of Scandinavia in the easterly flow (this type of minor feature as well as troughs and other disturbances cannot be accurately forecast a week in advance). It is dragging in some very low uppers and deeper surface cold behind it but this cold pool is moving our way anyway. Plenty of snow on that chart! The ECM output for the same time is pretty similar but with subtle differences which will be important going forward. The Iceland part of the HP block is about 150 miles further south. The LP is in a similar position east of the Azores but there is a much cleaner and rather stronger easterly flow with no LPs embedded in the flow (at this stage). This stronger more direct flow is pushing the lower 850s right across the country. On this chart I would say that there may be snow showers in the south and south-east. With the flow marginally south of east, there could even be a rare Channel streamer which would produce a line of snow showers near the south coasts of Dorset, Devon and Cornwall. I moved down to Exmouth 3 years ago from Hertfordshire and other than seeing a few flakes on several occasions, we've been completely snowless. INTO WEEK 2: Here, Ill produce the same charts for day 10, the furthest out that ECM goes: GFS: Jet Stream Surface Pressure 850 Temps 2m Surface Temps ECM: Surface Pressure 850 Temps The GFS shows a slightly changed jet stream profile. Most of the energy continues in the southern arm but there is a strange breakaway branch pushing into the UK. What on earth is the GFS reading here? They are trying to push the pattern northwards. They have mixed out the very cold uppers over western and central Europe and pushed the lowest values in northern Europe and Scandinavia. I have a theory for this. We know that the models find it difficult to cope with the impacts and pattern changes associated with an SSW and full wind reversal. GFS is trying to bring the Atlantic back in as if this was a temporary blocked pattern. This is definitely not the case. The Arctic pattern is still in full reverse flow mode and is unlikely to change back any time soon (perhaps not at all if the strat SSW and second warming merge into the final warming). This will maintain the blocked pattern. Yes the block will shift around slightly and the flow might back to northerly at times but the dominant pattern will continue to be from an easterly quarter. There is nothing to push the jet through the UK and the Atlantic will also remain relatively blocked. One cannot rule out a more south-easterly and less cold flow at times but the main cold block is much more likely to reload after each weakening, unless or until the Arctic reversal ceases. The SSW was so strong that it is likely to maintain powerful HLB for a prolonged period. . The ECM solution makes so much more sense. They do slacken off the easterly but the direction of the main flow is still north-east to south-west. The LPs around the UK are all cold ones originating from the north-east. Yes, it's possible that one of them might bring in "temporarily" less cold air from the south, more especially down here in the south-west. The 850s are still -8s to -12s and that looks like a particularly snowy period if that chart verified. DEEP FI - DAY 16: Just a brief look at how the GFS continue with the 12z run. GFS: Jet Stream Surface Pressure 850 Temps 2m Surface Temps They have brought the Atlantic to life again with a moderate westerly flow and uppers going into positive territory. The jet stream hardly supports this pattern accept that there is a kink in the southerly track which brings a loop into the UK. It might even be that GFS shifts the pattern back southwards again later on but that doesn't explain their very progressive or completely wrong attempt to bring the Atlantic back to life. The last strong SSW impact was in March 2013. Quite a different build up with it being triggered in January and no two events will have exactly the same impacts and timings. The pattern went into full reversal back then too and that lasted for 6 weeks despite the deeper cold starting some two weeks later (around March 10th). let's now see how GFS handled that one with actual archived charts and GFS archived predictions: GFS Archive Charts T+ 240 Forecasts, 10 days out: For March 10th 2013 For March 10th 2013 For March 20th 2013 For March 20th 2013 For March 30th 2013 For March 30th 2013 For April 9th 2013 For April 9th 2013 NCEP Re-Analysis Actual Archived Charts: Actual March 10th 2013 Actual March 10th 2013 Actual March 20th 2013 Actual March 20th 2013 Actual March 30th 2013 Actual March 30th 2013 Actual April 9th 2013 Actual April 9th 2013 Gosh, this was a trickier exercise than I imagined it would be. I'm afraid that you'll need to scroll back and forth to make the comparisons but I'll summarise the differences now. The GFS archive charts with their forecasts 10 days in advance are shown in the top two rows and then the actual charts for those same dates are shown in the bottom two rows. As you can see, there are considerable differences. The actual chart for March 10th 2013 has the easterly flow well established with -12c 850s flooding in. The forecast was for southerlies and +4c 850s. By March 20th the actual and forecast charts are a little closer with easterlies over the UK but the forecast had a stronger vortex remaining whereas the actual chart shows it broken up. The forecast had lower 850s for the UK than actually transpired. By March 30th GFS forecast had started to bring the Atlantic back in but that never happened - doesn'tthis problem seems very familiar! The forecast 850s were over +4c but the actual values were sub -8s! By April 9th, the forecast was for LP just starting to bring in milder south-westerlies but the actual charts shows east-south-easterlies! The forecast was for 0c to -2c 850s but the actual was -4c to -6c (a little closer). Overall, this exercise was highly worthwhile. It shows that the GFS constantly wanted to warm things up and bring the Atlantic back in but that never materialsed during the entire 6 weeks. Despite their model being updated, I feel that they sinply have not learnt any lessons and still do not factor in flow reversals. Now with all this evidence I hope that many of those who are worried about the longevity of the cold spell being cut short should not look at the GFS in the extended period. So far, most of the other models seem to be doing a rather better job but in fairness to the GFS, the others do not go up to day 16. So, let's just use the day 10 charts as the evidence. That's more than enough from me for now. I'll do one of my Eurasia temperature and snow cover profiles tomorrow (or Friday). EDIT: I'm afraid that the white "run through" arrows for the charts are not appearing. Not enough editing time to change these now. I apologise for the inconvenience and will copy charts in a different way next time.
  17. 69 points
    Well it's a wonderful sunny day down here in Exmouth and 12c right now and set to continue (here) for 4-5 days with overnight frosts but gradually cooling off by day. The south-east will be the first to see the cold weather biting and some early snow flurries (perhaps by the weekend?). Very few people will believe us or the MetO etc (and certainly not the Daily Express - crying wolf far too often) that we are heading into deep cold! This benign, sunny and mild weather reminds me of what proceeded many of our severe cold spells and I thought that it would be the perfect time to compare some of these to the current and predicted patterns. Before my time, it was very mild in mid-January going into the 1947 epic cold spell. At age 3 (before I can remember), it was very mild prior to the severe cold of early Feb '56. Then my actual experiences started with the '62/'63 winter. Some early cold and snow in November and early December. Then cold and foggy. Then mild and benign for a week and then from Dec 25th, sudden cold and snow and 11 weeks of winter wonderland. There are other and more recent examples, including February 1991 and March 2013 which some have already alluded to. What many of them have in common is the HP building into the country (either Azores HP ridging north-east, HP developing right over us or HP ridging down from the Arctic or Scandi). They all brought in winds from a southerly quarter with mild and benign conditions. Then the Siberian or Arctic (or in between) HP built and the wind backed into an easterly or north-easterly quarter. It actually all makes sense. Almost all of these spells started slowly and then the doors to the freezer were suddenly flung open. BEFORE AFTER 1947 1956 1962 1991 2013 2018 I believe that we'll be referring back to the 2018 severe cold spell as an analogue for many years to come. I'll be back with one of my Eurasia temperature and snow cover reports towards the end of this week. Everyone enjoy watching this all unfold. It's going to be something highly memorable.
  18. 68 points
    So, that's another couple of people blocked from posting in here, any more takers? Those wanting to just moan for moanings sake, please head to the moans thread. Those wanting to troll, please do one. Those wanting to discuss the models, please carry on
  19. 68 points
    Posted February 10 Irrespective of what the ECM goes on to show shortly and irrespective of what my head keeps telling me of how the effects of this SSW could be mitigated, I am not sure I have seen anything programmed quite like this thing. Polar easterly reversals are often enough mitigated at least to some degree by other tropospheric drivers, but I am beginning to come to round to thinking this may not be one of them where that happens so easily and its going to take over a lot of the NH for some time. it could be the case that it would start to be more prudent not to underplay the SSW, than place caveats as to what might mitigate it. On that basis maybe its me who should have a bit of a ramp, and not others who should restrain themselves However it plays out in terms of what comes out of the sky in the coming weeks - and despite the fact that the actual phenomena of SSW's is not new, this is quite a significant specimen indeed we are watching unfold ............................................................................ A week on, and a crazy amount of pages later, what has changed? Well I haven't had another ramp, and the deepest cold is still 9/10 days away But what has become clear in the course of a week is that the first stratospheric break-down salvo is set to verify for certain this week - and that day 9/10 day period marks Phase 2 and the time when the Canadian vortex to the NW should finally back off and the down-welling process of -ve zonal wind anomalies really start to make themselves felt in out part of the Northern Hemisphere On that basis we can give credence to the shape of the mid and higher latitude pattern and emerging block alignment with the deep cold backed up like a dam waiting to be unleashed I am amongst the most sceptical of day 10 UK deep cold in NWP and very often based on the realistic signals, barely take a second glance, if even much of a first glance at all But this SSW is a significant specimen indeed, and no further deep analysis is needed. On that basis I will be taking this particular day 10 deeper cold rathe more seriously as a contender The fact that Phase 2 marks the time when the strongest sibling vortex lobe starts to finally cave in after its winter rule, increases the chances of deeper cold air advection at that time-period not just because the block to the NE can start to orientate in ideal position as polar jet energy is finally being squeezed out, but because the chances of retrogression are also much higher so that at some stage re-loading deep cold has a heightened chance of finding out even this little Island. Probably the most simplified basic principle post you will get from me - but less is more sometimes and nothing else needs to be added
  20. 67 points
    Also.. Please remember that there are loads of unseasoned folks reading the thread so whilst your tongue in cheek comment might register with frequent visitors, it may well be completely baffling to most. It’s easy to think that the board is just the same 10-15 people reading and posting but there are 500+ on tonight. Don’t be a dick in front of 500 people, I guess is my message.
  21. 66 points
    Looking, or rather skimming through the last x pages from late afternoon, reiterates why I do not spend too much time in here. Some of you for goodness sake have a walk outside, watch the tellie, talk to a real person away from the pc. What you are watching is the weather models trying and slowly but surely, as they always do, come to a concensus about what is happening. Quite why folk worry about T+240 and beyond when most predictions by the models at that range are highly prone to change is beyond me. Deep cold is 85-90% likely to occur, it has never really been sensibly predicted by any of the more serious posters assessing the various outputs to occur before 23-25 February. That was two weeks out. Now within a week of the second date that is being refined to more like 25-26, so what? Get a grip and become realistic, they are models created by humans, are you perfect? end of jh rant. here is the latest link to NOAA 500 mb anomaly charts. This level, approximately 18,000 ft is far easier to predict than the surface, these are mean charts, but they are about 70-75% close to what occurs in about 80% of cases. Yes they are wrong at times but not often. http://www.cpc.noaa.gov/products/predictions/610day/500mb.php To me, using them every day for about 7 years and during the winter for 10 years or so I cannot recall seeing charts showing any more solid northern blocking for the time scale they are showing, this for at least 3-4 days. That includes the deep cold much of the country had in late Novemeber-December 2010.
  22. 63 points
    Anybody fretting about whether it's marginal, it's not even close.
  23. 62 points
    Ah those were the days, 'real' snow depths not your 1-3 cm and traffic chaos like now!
  24. 62 points
    Must say considering I have only been home a few days following a spell in intensive care, I am finding the output very pleasing and healing at the same time. Can someone bring me up to speed though. When was the potential E,ly first modelled and by which computer model. I won't be contributing much to this thread as im still very weak. Just enjoying the contributions from others especially Steve M who is equally obsessive about E,lys as I am.
  25. 61 points
    Hello to the Net Wx comic, I suppose it's not tea you are drinking A Good to see you on form and markedly misunderstanding the models as usual take care young fella oh just to confirm that the flow is going to come from east not west from later this week and into March, below the links to the latest NOAA 500 mb anomaly charts. They have been consistent for several days now with what they show this evening. Just how cold and how much snow not even Anyweather has any real idea. The synoptic models will to and fro about this over then next 4-5 days. So really interesting model watching. http://www.cpc.noaa.gov/products/predictions/610day/500mb.php
  26. 60 points
    The high goes further north and the moaning starts , it goes south and the moaning starts ! Seriously what’s going on? The GFS didn’t follow the ECM which is great news. I think I might come back when some sanity returns to this thread!
  27. 60 points
    Wow, some of you are like bloody toddlers. Either grow up fast or don't expect to be able to post in here for much longer, it's ridiculous.
  28. 60 points
    I don't think there are any words that can describe these synoptics, lol. All my SSW dreams coming true - this is the perfect SSW trop response that excited me so much 2 weeks ago. Can't believe that it can come true - Can it?
  29. 59 points
    I think BA is simply reinforcing the point that it’s not really worth attaching too much credence to current output, where there is clear inconsistencies being exhibited. It really is more about broader trend and the eventual path, whereas the journey to get there remains fluid and undecided. 12z EC could correspond with its peers or it could reinforce its 0z signal and advertise a more subtle path. What I would strongly disagree with, is NWP assertion of a quick return to mobility (or milder weather) That evolution doesn't correspond to mid range products at all, and can quite confidently be discounted as models reverting to type and to some extent underestimating the degree of in situ blocking. This behaviour has been seen previously so reasonable to view a rapid breakdown with scepticism. What an exciting end to winter! SB
  30. 58 points
    It baffles me how some are managing to find negatives in the current output. It is not being delayed, no idea where you're getting that from. If you can't enjoy the current output then you'll never enjoy any winter synoptic set up.
  31. 57 points
    If anyone has the patience to look through the ECM ensembles on weather.us, make sure you do tonight, go to Thursday March 1st, look at 850hpa / temperature and scroll through all 51 members. You may never see anything like it again. The number of runs bringing minus 16C uppers into the E of England is staggering, truly staggering. Probably 50% of the runs or more on either the 1st or the 2nd - it's the majority! It's only a few nutcase runs that is keeping the mean nearer minus 10C. A lot of runs get to minus 17C, and two runs even get the minus 19C line to the east coast. The number of UK wide ice days is also quite incredible, and you'd have to think the UK minimum daytime record for March (-4.6C according to the Met Office) would be under major threat somewhere.
  32. 57 points
    Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Get the cold in then the snow comes ... Everyone got the message yet????!?? There is NO POINT in looking at anything after the 3-5 day mark. It WILL change. * Do we have cold coming?? YES * Will any precipitation fall as snow and not be marginal???? YES ...Then yes we are sorted people!!!! Come back and look at precipiation from Monday morning onwards ...
  33. 56 points
    For those getting up to have a sneaky peak at the Gfs 0z go back to bed and sleep well. It’s awesome!
  34. 56 points
    What we are witnessing from the 18Z is a stunning synoptic evolution. Enjoy it.
  35. 56 points
    This is not the BBC forecast thread, please stop replying to the (already deleted) post about it! Thank you
  36. 55 points
    I've had a great idea, we could make some other threads and areas on the forum for people to discuss all sorts of other topics that are accessible with just a couple of clicks, then this thread can be kept to just model discussion? Oh wait....
  37. 55 points
    WOAH, WOAH, WOAH GUYS. I have NEVER seen a chart quite like this one... hold onto your pants... the Polar Vortex has only gone and turned FULL LOBSTER 😵😵
  38. 55 points
    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!
  39. 55 points
    ECM a bit disappointing tonight because any showers between days 8-9 could be a bit sleety..... ........(Can't remember seeing such a great run for a very long time if ever on internet)
  40. 54 points
    Afternoon, as promised reporting back with our Forecasting Portal Service experts latest thinking with specific the United Kingdom regarding depth of cold , timing and snowfall. They talk about the large cold block in place over much of Europe by Wednesday with Britain well locked in its midst based on the model 300mb wind flow pattern over much of the Northern Hemisphere which looks conclusive to a prolonged cold spell. Their own model develops a core mass of very cold upper air now developing over Northern Russia, sub -40c core at 500mb level ( at around 18500ft asl). They predict this cold pool to move W/SW in the direction of the British Isles with a quicker solution than shown by some of the bigger models. Further into the middle of next week looks like a trough or low formation to develop in the flow ,possibly over Poland or Southern Baltic as they have pressure value falling as low as 1015mb. That's something to keep an eye on in later runs. So light snow could start showing up in Southeast parts later in the weekend but the heavier convection snow more likely in Eastern parts in earlier part of next week with possible chance of more organised snowfall by Wednesday or the first day of the new month. So all in all follows UKMO latest forecast regarding snow prospects but the difference could be timing. Hope this all helps. C
  41. 54 points
    Comes in, has a little look at the 12Z GFS and has a little chuckle to himself.
  42. 54 points
    As always, to try and take stock of NWP means instead of trying to second guess it (and its ensemble suites) at face value, it means instead attempting to step back away from it and try and do an assessment of the factors that are driving it These factors are vast and hugely complex to say the least and there is literally no-one who can make solid definitive predictions, (though some may try regardless of course), based on such an extremely loaded atmospheric profile that has been pulled in two quite different directions over such a relatively short period of time. But that loaded state still has to be assessed against the fairly recent history that has been equally as volatile as the present - and may still have a say in the way ahead in the context of the SSW. The Global Wind Oscillation plot orbit emphasises the contrasting forces that have been taking the atmosphere in two very different directions one after the other over just a ~ circa 6 week period. Two high amplitude directions - one opposing the other. . We have seen strong easterly trade winds from late December and the start of the New Year plunge the atmospheric state into a deeply low angular momentum state reflective of La Nina registering a stronger forcing relative to the official weak base ocean state. This beefed up a profile of sub tropical ridging and more enhanced polar jet flow that kept an average to milder in the south and often colder in the north zonal flow pattern flatter than otherwise might have been the case. Then, in complete contrast to this, a record breaking MJO amplitude wave has subsequently attempted to imprint on the top of the robust Nina profile of January, stretching the atmospheric profile in completely the opposite direction with a markedly +ve AAM disconnect to the base Nina state instead of a markedly -ve one . This has seen quite a change in the zonal wind profile across the Pacific with MJO derived +AAM anomalies replacing the swathe of -ve AAM anomalies (La Nina easterly trade winds) We have been seeing this tropical momentum process work poleward since the last week or so of January and the signals for stratospheric upheaval come into play to join the highly stretched rollercoaster of opposing forces the troposphere has been subjected to. I am deliberately paraphrasing and dumbing down the technical processes involved here to keep emphasis on the huge complexity and conflicting natures of the pattern. These technical processes have been discussed in detail over many previous posts anyway If we take the above GWO trace plot at the top of the post literally, then NWP to date has traced it perfectly. Flatter, faster zonal under the low AAM phases 1,2,3 during January - and then increasingly amplified in the last week as atmospheric angular momentum has shot up with the Scandinavian ridge of this week verified - viewed of late as generally as an appetiser to something better c/o SSW. So far so good. But this is where it gets very very difficult and why some caution needs to be applied in terms of trying to read between the lines of tropospheric reactions to the SSW The ying-yang of the atmosphere and its instability related to the fixed parameters that govern its wind-flow exchanges between tropics>extra tropics mid and higher latitudes>stratosphere) are working on an intricate series of different timelines that take the representative synoptic pattern in the troposphere to different places at different times. Its here that we cannot ignore December and January's past history as much as we cannot ignore the meltdown in the upper atmosphere that is up-comimg The Scandinavia block hasn't sustained (as expected) due to the brief nature of the peak of the +AAM spike above. The direction of travel is descent from here - but how much? This is discussed further down. But back to the context of the SSW for a moment, because global tropospheric wind-flows (as measured by the GWO) and the net outcome of those (flatter -ve AAM flow vs amplified +AAM poleward transport) are to be measured against the polar -ve anomaly easterly period at highest latitudes that the SSW will be yielding (over however many days it has technical reversal) There is surely no doubt that a high latitude block of some kind will emerge based on a reversal of zonal winds at the highest latitudes - it would be counter intuitive to suggest otherwise. But what is highly uncertain and questionable is how the whole troposphere profile responds based on the possible default tendency of the atmospheric circulation to default to La Nina once again as the latest amplifying poleward tropical momentum transport process concludes. We cannot assume 100% that the latest poleward forcing c/o MJO will automatically imprint a sustainable impact on the atmosphere (and hence the tropospheric synoptic pattern) based on this alone. Contrary to what is often assumed on here, MJO lags alone will not account for all this - we have to take the extra tropical reactions into account as measured by the GWO. On that basis we cannot make assumptions of sustained cold pattern verifications based on dateline convection if the extra tropical GWO is not conducive to this. Feb 2009 with its noteworthy SSW and very fast response time in the troposphere did not actually sustain anything like as long in terms of cold air advection to this latitude in terms of depth as its strength of destruction, but was instead diffused and watered down beyond the initial Scandinavian High pressure that gave the easterly and snow in the early part of February. There was something of a disconnect between the high latitude block profile over the polar field, and the pressure arrangement across our mid latitude which didn't reflect the type of classic -NAO response and undercut looked for in terms of sustaining a cold spell. Ultimately, a WQBO and La Nina profile thwarted any sufficient weakening of the +NAO profile. This winter so far, irrespective of E/QBO state, we have again seen how low angular momentum regimes when unsupported by amplifying actions of tropical MJO forcing (changing the traditional Nina profile of the Pacific trade easterlies) have easily reverted the atmosphere and tropospheric state to an unremarkable one at our mid latitudes. In many ways we are in similar place to where we were at the peak of the last tropical MJO phase in December - where the route to follow of AAM is always down - towards the return of the MJO to the Indian Ocean and start of the next phase. The difference to then, and it is of course quite a large difference, is that we have implosion forthcoming of the stratospheric vortex. Its hard to envisage absolutely nothing exciting happening isn't it? Isn't it? To take NWP into context, and why despite some charts which do suggest it will do what is expected and anticipated and yet others seem (almost annoyingly out of spite) seem to keep a stubbornly underwhelming profile, its necessary to look at how far angular momentum might fall back again at the conclusion of the latest MJO wave, however huge it has been and however imposing the SSW may look. Total GLAAM, relative to where it was at -3SD has sky-rocketed as shown in the timeline plot above - and best reflects the sheer size of the poleward tropical momentum transport that has taken it there. Another measure of the latest +AAM forcing is the Southern Oscillation Index (SOI) - spiking as much -ve now - as it was +ve during January https://www.longpaddock.qld.gov.au/seasonalclimateoutlook/southernoscillationindex/ The plot above for the GWO illustrates how rapid the orbit continues to race through the higher AAM phases - and this reflects the default reality that although showing distinct signs of decline, there still remains a La Nina signal firmly in the background to steer AAM budgets (net total global wind-flows) and suggest that an easterly trade wind bias *may* try to re-emerge around the time the SSW is trying to flex its effects in the troposphere. How much, if at all, this happens will have significance on the mid latitude profile and either offset or assist the tropospheric effects So its way too early to know, but any drop-back in AAM *might* be a factor that *could* work against effectiveness of blocking at our latitude and, such as happened in Feb 2009 under weak La Nina, with some residual splintered pockets of vorticity aligning some stubborn polar flow that scuppered sustained cold air advection furthest south- beyond the initial easterly. The significant snowfalls of that event are remembered, but what is less than remembered is that it was relatively unremarkable to follow Its hard to be sure at this stage, but set against the effects that the latest MJO will have had in terms of moving warmer waters eastwards from the Western to the Central and Eastern Equatorial Pacific, and also aiding upwelling of warmer sub surface waters (and hence limiting rather more any resurgence of easterly trades), then this, plus the legacy of +AAM anomalies scrubbing out so much previous easterly Nina inertia in the atmosphere should be enough to prevent angular momentum falling back too far. Ideally though, at least in my opinion, the best timing for the SSW would have been in the last 10 days, in tandem with the massive AAM surge and GWO in most amplified phases. All possibilities, including good ones remain, but I think its important to gauge the SSW against what has been and gone and how the cyclical nature of the atmosphere may influence (mitigate or enhance) the tropospheric effects of the implosion within the polar field. On a thread which is, alas, hyper sensitive to any pitfalls and resistance to anything that doesn't suggest cold - this is simply, as per usual, a little heads-up to the type of thing that might happen. Its because of this that so many of the key words are italicised. History always shows that such a sensitive emotional environment as this leads to all sorts of misconstrued and knee-jerk assertions further on. One cannot manage expectations and thrills and then disappointments for others for them, but it is possible to try to do ones best to tell them in advance. The rest is up to them.
  43. 54 points
    Remember reminder: Its only an island if you look at it from the water Feb 2018 : Massive poleward tropical momentum transport + tidal surge of +AAM tendency > +MT > fast orbit Phase 5/6 GWO Nino attractor in extra tropics (this weeks easterly 'jab around the edges') >stratospheric pathway dissolution/feedback from dateline convection > -AO/-NAO. Allowing for some deterministic model variations of forecast, based on the fundamental changes that are underway in the Pacific eastern and central waters, good supporting reason to 'cherry pick' the ECM to illustrate impending ultimate change downstream in terms of the state of Annular Mode I don't make forecasts as such, but lets just say the Global Synoptic Dynamical Model (GSDM) timetable is evolving very close to its defined timeline schedule from inception date ~ 22 January when the starting pistol was fired in the tropics c/o the MJO and the poleward momentum process was underway. The extent of the extra tropical +MT propagation sure reflects the huge amplitude of the tropical convection rossby wave trigger Back to a previous posted comparison made in last 2 weeks: Feb 1978: Spent most of the month in GWO Phase 5/6 c/o high amplitude MJO and led quickly to a strong -AO/-NAO combination. Differences? There was no La Nina lag underpinning an entrenched sub tropical ridge +NAO pattern and so the tropospheric/stratospheric pathway was unhindered to a much greater degree. Well, that and of course the absence of so much anomalous homogenous warming of tropical oceans which are skewing and rather neutralising the natural effects of strong tropical poleward feedbacks - in addition to the alarming atrophy of sea ice which correspondingly unbalances expected albedo feedback relationships to an increasingly unprecedented state : Feb 2018 is indeed proving to be a slower burner with, overall, increasingly less cold air relative to 1978 in the NH to share around in terms of cold air advection from the pole and which inevitably therefore favours much less dilution through continental landmasses like Canada, than downstreamacross oceans) But, all that said: There is an abundance of pretty cold air to the NW as we watch the next phases of trough disruption. Based on the spatial arrangement of cold vortices which look set to ultimately implode - that doesn't mean (by any means) that the UK and Europe won't yet see their coldest weather of the winter, as the end of official winter gets closer and closer March 2013 provided this on the Costa del Cinq Ports of the SE: It was even worth capturing some So, still very much the sort of thing that is more than possible late winter 2018, a few weeks earlier than the fun and games of March 2013 - and so there is no need for anyone to be miserable
  44. 53 points
    Dear forum members, For the hardship caused to many of you over the weekend period by my, what I can only describe as, schoolboy efforts: I would like to offer the below as a means of apology... I hope you will see it to yourselves that I was having a bit of an off spell, having been out on an all night bender on Friday night with the GFS 18z. I believe I have learnt the error of my ways and hope we can continue on, as we left off, before this whole sorry debacle. Yours, The ECM
  45. 53 points
    Musing about Feb 15. Amy Butler has tweeted an expectation that the SSW of Feb 12 will begin to force storm tracks equatorwards after about 3 days. This is the ECM for the start of that potential process I'm seeing very cold air dropping into the mid Atlantic with pressure rising to the north and Scandy pressure also I suspect on the rise. Storm track set to shift further south as impacts of the reversal are felt and cold begins to tumble southwards. Is this the precursor to the mother of all undercut scenarios?? I wonder what ECM would look like for weekend of 17/18. A bit of southerly adjustment and this would be the biggest blizzard since... well.... the last time we had a big blizzard. Hmmmmmm.
  46. 52 points
    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..
  47. 52 points
  48. 52 points
    Irrespective of what the ECM goes on to show shortly and irrespective of what my head keeps telling me of how the effects of this SSW could be mitigated, I am not sure I have seen anything programmed quite like this thing. Polar easterly reversals are often enough mitigated at least to some degree by other tropospheric drivers, but I am beginning to come to round to thinking this may not be one of them where that happens so easily and its going to take over a lot of the NH for some time. Its one of those very occasional cases in point where referring to the direction of travel of the GSDM is certainly not the whole story when it comes to tropospheric forcing and the placement of the jet stream, set against such a considerable reversal of zonal wind anomalies coming into the troposphere. So on that basis, putting aside what my head has been telling me, it could be the case that it would start to be more prudent not to underplay the SSW, than place caveats as to what might mitigate it. On that basis maybe its me who should have a bit of a ramp, and not others who should restrain themselves However it plays out in terms of what comes out of the sky in the coming weeks - and despite the fact that the actual phenomena of SSW's is not new, this is quite a significant specimen indeed we are watching unfold
  49. 52 points
    Indeed. Stark correlative response from stratospheric influence. This is an interesting one as GS usually ranges a warming signal circa >20 days, so immediacy is unusual which is influencing CF’s confidence re LR synoptic. What is without question is that there has been some quite remarkable perturbations, and strongly balanced towards a very much colder pattern. If downwelling is as rapid as is being considered, it is plausible to see large scale continental blocking patterns dominate for quite an extended period, and very conceivably into meteorological spring. Should see some interesting runs this week, that’s for sure! SB
  50. 52 points
    I don't normally enter this upgrade downgrade pantomime but just for fun I have had a careful look at the 06 and 12 z outputs. To me there is nothing I would call significantly different in the overall pattern until T+168 h. Tell me how often any model, we have 2 we can see regularly GFS and ECMWF,, that are identical after 120 hours let alone 168 hours? Okay if you want to have the roller coaster every 6 hours but try to put some objectivity into the comments please. Re will it snow or not. Think back to how accurate any model is, or indeed professional forecasters presentations are about when/where/how much rain will fall in the summer, even just 24 at times 12 hours out.believe me predicting rainfall compared to snowfall is a doddle. Wait for 12 hours out, watch the radar, you are far less likely to have a mental breakdown that way. It is going to get colder and experience tells us that we ALWAYS try to shift the block of cold air too quickly. It used to be just the same prior to models arriving. Just a time difference, then all we could do was forecast 24, at a pich 48 hours, ahead. Now the models give outlooks days ahead. Think about how hard a solid lump is to shift with warm water, on a huge scale that is what the atmosphere is trying to do to a cold mass of air. sorry to natter on but it is model related.