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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)

I know im late to the party BOOOMMMMM

Time to take stock... Stratospheric split complete, reversal in operation - ECM 10 day forecast for the lower strat is significant With clear signal for the expected nose of high pressure through the north atlantic, with virtually no westerly impact at all across Eurasia and a canadian vortex under stress from warming over Greenland. No downwelling support for an sustained atlantic assault, that's for sure. At the tropics an interesting picture: tendency of equatorial angular momentum may have bottomed out and with MT turning strongly positive we have a current signature for GLAAM not falling too far or too fast. This may keep momentum positive over the longer term (lots going on here... is our Nina fading fast?? MJO renewal over the IO set to follow pretty swiftly??) and help maintain sufficiently low momentum profiles over the north atlantic to encourage the block further to the north. In layman's terms what does this mean? Complex. I think Feb 2018 might be a much discussed month, dissected and reanalysed many times by students of SSW and GSDM alike - but the best guess at present remains the same as was the case over 10 days ago - height rises to the NE and a storm track pushed to the south underneath the block. This to retrogress over time, so heights transferring from Scandy to Greenland. This may not happen at the first attempt next week (though it might....), but likely on the second shortly after. Evidence? I think op runs will be chucked all over the place tonight - so let's instead look at 3 key ensemble charts. Firstly CPC human adjusted chart that is usually a strong guide - 6-10 anomaly favourable with EPS for day 10 also very good and GEFS in line, though rather less strong in profile Conclusion? CPC + ECM + GEFS (moderately) + strat profile (SSW, split and canadian vortex under stress) + pacific pattern (more neutral than supportive... but not overly negative) = a strong pathway of support pointing to cold inbound. Mid week as the jump off point, but early enough for snow lovers to get a fix before spring arrives, and longevity might be notable. Too early to be sure on that yet, but I dont think the trop pattern will recover swiftly from the present SSW.

Christ give everyone a minute to enjoy their passion. The majority knows the caveats but this is what some of us stupid cold fans live for! Cmon....

Oh GFS FI

ECM Ens are a win.. not in the same ball park as the failed 41/51 reversal either from a few years back. Am just looking forward to the utterly manic run the 18z GFS will deliver, I thought a few days ago it would, but it will now for sure.. That is simply the only run that will eclipse tonight 12z - truly stunning ECM, it's late to the party, but in the big scheme of things the facts are - it is the best hi lid model, it's the best verifying model, it's the best model to 144, and, its the best model... So, all in a massive plus for those on the hunt for cold, the vortex split dynamics have telegraphed the supply of cold, the trick is in the development of the block. Tonight sees the ECM move to resolve the split energy and recognise the break, perhaps to the outer envelope or extreme cold solution tonight - but it is what one could expect to see given the stratospheric chasm and nuances into 150 hPA. Further to this, regarding the initial QTR - the strat evolution plots and the dead drop bounce on u are mental to resolve. Probably the cause of the chaos of the last 48 hrs. We know the u is in reversal , yet we see the deceleration on H Attard plots and acceleration again, no model will resolve this, until it plays through. Tonights ECM I think has seen that initial trop bounce, u wind rebound and play through and therefore it's higher top and resolution latch onto the 'truth' and the reality of the split hence the that x3 ecm run. Just think now the ECM has 'got' this... what lies ahead for the other models...

In work.

here's the Brazilian model- that's a close shave....

I think the missing data part could actually be a factor here, I'm assuming that some of it's 'shared' and perhaps, just perhaps ECM decided to wait vs the other models running with what they had. Given the unique state of the atmosphere it 'makes sense'. Oh and I think its written in the stars... I was on a train back from Derby last night and happily browsing the forum when I looked left and noticed the chap next to me doing the same, what are the chances of 2 weather geeks sitting next to each other on the same random train? We had a little laugh and chat about how this is all going tits up and then boom I check the ECM on my next train and we're back in the game.

A mere 45 mins ago posters were giving winter the last rights then ecm bursts in the room with a defibillator

I just wanna tell you how I'm feeling Gotta make you understand Never gonna give you up Never gonna let you down Never gonna run around and desert you Never gonna make you cry Never gonna say goodbye Never gonna tell a lie and hurt you We've known each other for so long Your heart's been aching but you're too shy to say it Inside we both know what's been going on We know the game and we're gonna play it

Greeting from a sunny Austria. View from apartment towards Tshneck run. Feels a bit warmer today with temp just above freezing. Just had a chat with our portal forecast service providers with specifics regarding the UK outlook. Like most forecasting agencies the present SSW has created a fair bit of confusion as confirmed by the present model outputs. The divergence in models is quite acute even at 84h as highlighted by the latest Arpege run that switches the flow dramatically from Westerly component to Easterly in a matter of 48 hours. My question to the duty forecaster is "where do you stand in your thoughts " ? Answer, Err difficult that one, however their best advise is now follow UKMO fax charts/Arpege out to 72h as their own model shows the same great uncertainty in its outputs. Human input is now more than likely to feature in the forecasts as the model diverge is too great at the moment/ Final observation , they think increasing chance of much of Europe to go into freezer by Day 6 at the latest ( hopefully blighty included ) Hope this helps a little!

*stop press* *Weather Agencies upgrade models due to SSW* Big news today folks as the major weather agencies proudly announce 3 new super models......Heide Klum, Cindy Crawford, & Ellie Macpherson....A spokesperson at met office was quoted as saying "in this current volatile climate, we feel that these 3 new super models will give us our best chance of resolving the SSW dilemma, we have faith that Heide, Cindy & Ellie can take our knowledge to a new level and besides, it'll make the office calanders look far more attractive".........Asked why the UKMO, GFS & ECM hve been dropped, he replied, "after viewing the overnight outputs all our senior forecasters can think of is white powder, flip flops & prozac" well, that's my take on the current model outputs folks, it's a mess, but joking aside, quite a few pro's have been tweeting for quite a few days to take all output with a pinch of salt, FI's at T96 IMHO, have a lovely day!

So what are we calling this one then That, That, THAT ECM.... Whole weekend of potential other That4 Ecm's ahead too ! SSSSSSW - Stunning !!!!!!!

Ho hum - this thread the last couple of days has been a case study in reactivity. The variations in model output ought to make it clear anyway, but just in case it helps to state the obvious: the fluctuations in stratospheric data, and issues with speed of downwelling, means that the models are having a nightmare resolving next week. Add to this Pacific forcing that is losing the high lat signal as every day goes by (falling AAM at present) and the cocktail is complex. Just go and browse the Berlin site for the zonal wind and vortex profile -it is shifting all the time on ECM and as a result the trop pattern is uncertain. It is still the case that the stratospheric profile indicates height rises to the north. This process has been pushed back a day or so from initial indications 10 days ago... but it is still in place. It is counter intuitive to see a substantial return of the Atlantic, especially given warming of the Canadian vortex shard, and even if falling AAM at the equator helps keep the block more mid than high lat in the short term, the direction of travel remains good. Take a deep breath. There are good reasons why the MetO is solid. The only negative for me is the fact that we are so close now to March... but beggars can’t be choosers and as I haven’t seen any snow for 5 years now I am very happy to be a beggar in this current scenario!!!!

You must be watching a different GFS than the one on my screen. Pressure differential is higher - block is stronger, low to the south deeper....

I’ve hust scuppered any cold outbreak by telling my family we will be snowed in for weeks. Will I ever learn?

Horrible ECM run I wish it would stop churning out these mild outliers!

Anddd Greenland retrogression! ECM would have the UK locked into cold for at least 2 weeks with widespread heavy snow. No marginality, powder snow for many. Incredible run and quite frankly, the very best outcome that we can hope for.

Just a further thought to the above, forecasts this evening from the computer models now all now showing cold outlook on the agenda. Now SSW has taken place, it sometimes takes up to 10 days for the full cold effect to take place. Our service provider think 70 % certainty now , which is in the high category . Of course timing and depth of cold is still on the cards. Still could switch quickly ( with 96h time ) or more likely Day 6 into the freezer. Fax viewing is now the best option to watch the developing cold and speed of advection. Short wave positioning to the East could also impact greatly as to source of cold ( ie) Arctic C or Continental flow ). C

Morning All The ECM is amazing - The UKMO is dreadful- what do you pick? What a dilema, - I think in all honesty the models have beaten us here... No point in really making a forecast - both models could be correct as both are plausable outcomes... Could there be a middle ground ? not sure about that- -14c at 216 -Todays run becomes the new 'That ECM' @That ECM

Yes - I think we are beginning to see the op runs correctly resolve the complex data aloft, result of ssw. Precisely how far north the blocking high will setup is still a little up for grabs, but the fading of the Atlantic is bang on schedule. Vortex split and reversal has knocked the stuffing out of the global pattern with temps rising over the arctic and cold air spilling out south. And the longer we look at the nature of the split, the more it would appear that we may have rolled some good dice... because while the very coldest air will reside over in Canada the destruction of the Siberian shard is going to allow the increasingly negative AO to drag a very cold flow westwards underneath the block. In these circumstances the block won’t sink, and the westerly pattern will fizzle out. I hope this doesn’t happen so fast that we lose any chance of battleground snow for the west... but precipitation amounts and location we all know will pop up at short range. A full on frontal fall via undercut of the block would be the best scenario. More patience required. This has been a while coming... my fingers are all drummed out... and there will be more model swings still to come... but I think we are homing in to a special end to winter.

Now we are starting to see the sort of charts that we would expect to see with the massive SSW starting to filter down and completely upset the default NH weather patterns. The GFS is absolutely stunning. The GEM is absolutely bonkers. In keeping with this week, it is safe to say we all know what the ECM is going to do now then, a Bartlett slug or blowtorch SWerlies? Joking. I suspect it will be good (don't hold me to that though!).

the GFS is on a wind-up isn't it?? it should be called the F F S!

For those that are interested, as I type this, the coldest area within the stratosphere anywhere around the globe is now, directly above the United Kingdom. At a pressure setting of 10 hPa, there is a minus 20 degrees anomaly. Above the UK at 10 hPa (101,000 ft) it is showing MINUS 69, the coldest area above the planet within the stratosphere.

I would love to see this cold come off as much as the next person, BUT, If I had a penny for every time i've seen BOOM turn to GLOOM over the years, i'd have my own chalet in Courchevel and wouldn't need to read this thread! Caution still needed folks

Hot off the press.... Nick's latest blog, on the model mayhem happening at the moment.. SSW Brings Weather Model Mayhem

Only about a -12C 850hPa anomaly expected... poor show - LOL

Well we do have an easterly starting in just four days time. If the ECM is correct of course. That said the middle part of next week looks bright with maybe a couple of wintry showers for the south east. But by now we have that Euro low developing with the high going over the top. Given the background signals we shouldn't see your usual sinker from here with further cold air pushing south west from the deep cold pooling over Russia. There is a reason why we are seeing multiple operationals toying with this, as well as the Metoffice repeatedly stressing the risk of significant snow. There is a real risk of severe cold pushing in from the east, enough so that the forecasts have to stress the risk despite large amounts of uncertainty. Personally if we get to this point in four days time then I think that parts of the south and east could be in a spot of bother.

That ECM is the best run I've seen in 10 years of model watching. The type of cold you would sell your grandmother for!

Hmm looks a bit dry

Like really, enough!

maybe for now we should just stick to hi-res short range models for the time being. try to analyse the smaller changes which may lead to the bigger ones. the 00z run of the Arpege is very similar to the ECM- as for the GFS... maybe all this rapid changing data, 4 times a day, is burning out their server....

EPS and GEFS T850s are like chalk and cheese. I can guess the sort of issues that will be having on trading floors right now .... There is a continued shift towards a re-invigorated convective signal in the Indian Ocean. Phase 2 MJO. During December and January, such a trend would be what we have seen overnight from the GEFS and other operationals. However, we are not in December or January and we are nearly at March. That poses all sorts of seasonal wavelength issues. GEFS mean days 11-15 remains relatively consistent with the EPS and its previous runs, its just the 850 values being elevated. GWO phase 2 for March highlights the dichotomy in model interpretations right now.. Let's put that (tropical only) MJO composite against the GWO (tropics + extratropics) side by side for comparison. Model fog continuing I think, but thoughts would still be for a more genuine -NAO (and associated temperature signal) and more particularly the closer we get to the end of the month.

I'm always happy to admit when a theory goes wrong and yes, the GEFS, having been rock solid for 6 days, have ripped my theory to shreds!! Having produced a very good Scandi High anomaly run after run, it trashed it on the 12Z and has not gone back!! The ECM ensembles, on the other hand, are still keeping to the script! They never went as extreme as the GEFS on the Scandi High, veered slightly run to run, but pretty much stayed bang on for the Scandi height rise after 22nd Feb. And, as one would expect in an anomolous situation, they are growing in strength as T0 approaches. So I feel the "trust the ensembles" mantra is both holding true and not holding true ... depending on which outcome eventually verifies! But when you have this short of difference on the MEAN charts at D4 ... you know you're in serious trouble. I mean just where is that Atlantic low on the GEFS?? :o But Hey, it's SSW season!! We've been here before. We know how it works. Have we ever had a major SSW without the models going loopy? They've all had to do the walk of shame during an SSW in the past. GFS: 1st February 2009: T168 vs T144 ECM: 18th January 2013: T144 vs T96 (!) Even the UKMO: 11th March 2013: T144 vs T120 And with that in mind, it's probably worth looking at the T144s this morning and taking a pinch of salt from the saltshaker - then come back tomorrow morning, compare with today, and chances are you'll have a giggle.

For all the confused emoticon responses - this is a bona fide greenland high being programmed as a result of the MJO wave analogs- hope that helps

Ive only just got round to viewing the ECM tonight, kids birthday party! But oh my goodness it was worth the wait!!! And a very enjoyable 8 pages to catch up on. I am staggered that even with those charts there is still some glass half empty posts, some people could win the lottery and not be happy lol! Just wow I guess the only concern is how on earth do we get upgrades from that! ?

So here we are - with an ECM run in our minds (and hearts I suppose!) that is perhaps as good as it could possibly get. So we must be realistic about what to expect tomorrow - even something akin to this morning's ECM would be pretty good going really although yes, I would feel a little disappointed at the longer wait even so. Only human after all . I do find myself thinking 'if only the UKMO 12z had been more enthusiastic' but actually, it's very similar to the 12z GFS days 6-7 and that run worked out pretty well in the end (...!). So as of this evening we have the following possible outcomes on the table from the operational runs: A quiet spell and then some deep cold (GFS 12z and perhaps UKMO 12z) Quick cold then too much Atlantic interference (GEM 12z) Quick cold then deep cold (JMA 12z and ICON 12z, both with extrapolation beyond day 7/8 ) Very quick quite deep cold then very deep cold that lasts for at least a few days (ECM 12z) Eagerly awaiting the updated day 4 FAX...

Can’t see any dp’s close to zero (in case anyone thinks you’re serious ed) what I can see at T210 over Holland are dp’s sub zero F !!!!!!, wow!

Sausage? That's a frankfurter

The ecm mean in animation,the op was a cold outlier though but the mean looks cold anyway De-built ens,temps, dewpoints and wind direction my word here is us in a week or so's time,if it comes off.

Very exciting ECM run so far. Lets hope the UKMO can come on board as that’s still a concern. To think I was eating lunch outside today in 21 c and sunshine , in less than a week close to freezing with snow . Everything crossed that just for once one of these sensational charts will verify and deliver some great end of winter cold and snow for the UK.

We have a thread open for the potential cold spell thread now, for those wanting to chat more generally about it without just talking about the forecasting model output.

And the saga goes on and on! Back from my day out , the medics gave me a pass at last! I don’t know what the UKMO is on , I don’t think it’s a sinker though , if you look between day 6 and 7 the direction of energy coming out of the ne Canada is more south se, it’s likely the day 7 would show troughing held out west with the eastward side near Iceland pivoting further north. The GFS is improving in two consecutive runs so at the moment a decent start to the evening .

Well as regards to my wrestling......GEM has just done a Dwayne ‘Rock’ Johnson on thr flatter opposition. I’ve always rated the GEM.....always BFTP

Not much to say really

Yes, it is slippy out there this morning! I'm doggy sitting today and daughter brought him down at 8.30am and took him out to the garden. When I looked out, she was lying flat on her back on the path and the dog was happily scoffing the treats that fell out of her pocket! God, I wish I had my phone to hand before she managed to get up! Does that make me a bad parent?.......Aw who cares, it was hilarious! 3c/1.2c.

"Data issues" you say.....a clear sign that @nick sussex is running dangerously short of netweather branded prozac and has had to bust his way into the control room at Reading to deploy his last resort - some custom data. He even did a great job of trying to make it look realistic by drawing the -6c 850mb line right across the M4 at T+240: For those saying they can't remember the last time the models were this volatile at such a short lead time, I can sadly - December 2012. Though in fairness then, the models did, one by one, drop the idea completely rather than flip-flopping from run to run. By the way that op run, whilst looking impressive, at face value isn't all that snowy until that potential undercut right out at 240...but let's get some sort of agreement on pattern first before we look at anything like that

OMG it keeps on gettiing better 168 192 Massive cold pool moving west And then ladies and gentlemen, I give you the 216. THE chart of the season

Very true. The SSW early this week has caused the stratospheric polar vortex to split into two, with ‘daughter vortices’, one larger one heading over Canada and the other smaller vortex wandering into NE Europe. But the models may have some resolution issues around the tropopause where the stratosphere – troposphere coupling takes place. The NWP model performance could be compromised by their limited resolution of handling of the movement and strength of the daughter vortices and how this imprints on the troposphere and thus upper flow configuration that drives our weather patterns. The NE Europe vortex looks like moving west but remaining detached from the stronger Canadian vortex –which itself may endure weakening as further wave breaking working up from the N Atlantic domain of the troposphere impacts the vortex. It’s how the models handle and correctly model these interactions that maybe causing to exhibit wild swings, which could ultimately be to do with how individual models are calibrated. So, lots of uncertainty in the forecast for next week, so weather apps and online automated forecasts from the likes of BBC, Met Office or those that use the GFS like Netweather the layman may find unreliable as they keep changing. So here is where some human input may be valuable trying to decipher what is going on by using ensemble guidance which is more reliable at such lead times, but also using empirical forecasting techniques and analogues of previous stratospheric events against similar background atmospheric states (such as La Nina, easterly QBO and low solar activity like now). A SSW, more often than not (66% of the time) leads to blocking high pressure to the north or northeast of the UK bringing colder weather than average some 10-15 days later. The current SSW still looks on course to bringing just that, given favourable background state, though we may have to wait until the very last few days of February or early days of March to experience deep cold and snow.