Snowaddict

Hi Snow Queen, I'm one of the biggest cold rampers around so I hope it isn't either... I really do hope that the ECMWF evolution is flawed... Excellent GFS 18Z out to T+96..

Steve, is it your opinion then that ECMWF evolution is flawed? Take GFS @ T+96, the differences are just simply astounding... Bitter easterly once again on the 18Z.. Do you have any further info on that potential flaw in this evening's ECMWF as mentioned by a previous member?

This information sounds very interesting regarding ECMWF... I only hope that it's correct because although synoptically up to T+168 ECMWF is not bad this evening, it's far from what we have seen advertised on the other models & is a VERY significant shift compared with alternative guidance.. I cannot understand the disparity between ECMWF & GFS at such a close timeframe: For example: 18Z GFS Operational @ T+78 850's of -4 approaching Ireland, all across the UK with -8's approaching SE England.. If this does go the way of ECMWF as modelled on today's 12Z run then it's a complete failure for GFS, GFS Parallel and it's ensemble suite.. @ T+84 there is a very cold easterly setting up across the British Isles on the 18Z GFS run.. VERY strange disagreement as such a close timeframe... But history tells us that the ECMWF evolution will be favoured unfortunately.

Some sensational snow events on the 06Z Parallel Run.. In fact, several feet of snow would fall widely across the country.. In the somewhat more reliable, it looks like rather heavy snow could be falling by late next Tuesday if GFS were correct.. Time for this forecast yet?? A STUNNING 06Z GFS PARALLEL RUN!!!!

Can this 06Z run really be trusted though in fairness? It's a fantastic run right from the beginning all the way out to T+168 with another reload from the northeast. It looks too good to be true... (But I hope that it's right!).. Snow showers into Ireland by early next also if it's correct..

There is no point in looking past T+144 in my opinion because we don't even have uniformity at T+120 - T+144 as shown on the 06Z GFS evolution... It has upgraded the initial easterly significantly with potent cold 850's, of almost -12 into SE England at T+120. -8's across the rest of the British Isles.. That would easily lead to snowfall late next Monday & on Tuesday... However, we don't have the same agreement from other models entirely.. Overall, prolonged cold looks like being highly possible, a lot more uncertainty regarding any potential snowfall. If T+126 on this morning's GFS 06Z were to verify, it would be bitterly cold within 5 days time..

Stunning set of 18z ensembles, even at T+120 with the HP cell cut off to our immediate north, ridging Northwest. First set of ensembles on which the mean also reaches -8 in Dublin, indicating increasing continuity for the westward progression of deep cold air... It's hard to believe what we are seeing really as if this verifies, many parts of the country could well experience significant disruption...

I am as excited as anyone however we just need to wait another short while to be guaranteed. I would urge extreme caution as some people could become depressed if this one goes wrong!! Ensemble agreement of -6 850's into SE @ T+96... It's looking fantastic at the moment but caution still advised. SA :winky:

Fantastic Parallel Run Steve.. We have that secondary low at T+162 dragging in the air much more quickly.. It would be bitter with copious amounts of snow showers and longer outbreaks of snow. Also, for the more reliable timeframe, -8's into Southern England which would still lead to VERY cold conditions for the time of year. However, we are not there yet & so caution is advised because I think that now we are getting closer and closer this would be THE biggest letdown ever. Fingers crossed everyone as many on here, myself included, treasure these synoptics.

Hi Sundog. Well, as ever with any cold spell that originates from the variable east, eastern, northeastern and southeastern areas will have the best chance of seeing some snowfall. However, Ireland would be a good T+16 to T+24 hours behind the UK in receiving such snowfall as the cold upper air would need to successfully back west... If the setup as modelled on tonight's ECMWF or other guidance does indeed occur I would expect snowfall off the Irish sea, with the possibility of more sustained outbreaks from embedded troughs in the flow.. In addition, if the cold air becomes entrenched enough across the British Isles, southern areas of the country in particular would be at risk of a significant snowfall even if fronts were to approach from the Atlantic. In fact, all areas would be at risk of frontal snowfall if the cold air was deep enough and became entrenched for long enough. Overall, I'm very pleased with the latest NWP guidance, however I would say that caution is still very much advised. For example, if the GFS evolution was to occur we would be at risk of flurries early next week, however it would be mid week before snow would arrive in line with the ECMWF evolution. Unfortunately it's too early regarding snow etc but the general idea of cold, potentially sustained and severe cold, has strong credence tonight... By next Sunday into Monday it should begin to feel rather cold. Just think, with so many fields flooded after the weeks of rainfall we may have quite a few frozen landscapes around if the latest output were to verify. SA

Again, we see a different evolution on the ECMWF 12Z run but that's extreme cold across the British Isles. Again, although we don't get real cold uppers beginning to approach until Day 6 onwards, it will already be turning MUCH colder from T+72 and T+96. If anything like today's ECMWF run was to verify, then there would be extreme cold, with extreme snow & we would be locked into a sustained, prolonged and severe cold spell. Overall, stunning outputs again this evening but I still think we need to be cautious as there will be more ups and downs yet!

The latest GEM T+120 also has 850's of -8 over SE England, with a widespread cold pool across the British Isles, along with a Shortwave beginning to drop down from Scandi (just north of Norway at T+120). That's the 12Z: GFS, GFS (P), GME/DWD, GEM, UKMO. That's fantastic, even stunning agreement, even at T+96 with the colder continental air well and truly arriving..

If this run were to verify then there would be widespread dirsuption to transportation across the majority of Europe, especially Scandi which would be shut off but also across the entire British Isles... I would agree that after T+168 the evolution is a bit more dangerous so to speak, because if a low were to power up to the southwest then it could be troublesome.. However, the 'weight' of that much cold air in place should mean that things remain very cold.. An absolute stunner of a run.. It's just unbeliveable that we are seeing such synoptics, beginning firmly at T+96...

For those who are worried about UKMO @ T+144, myself included, perhaps some comfort can be taken in the fact that GME/DWD, which was trending along the lines of UKMO this morning, has now reverted to a strong easterly flow by T+132, with lows cented well to the south and no mixing of cold air with TM air: http://www.meteociel.fr/modeles/gmee_cartes.php?&ech=132&mode=0

Paul, I will also disagree with your inerpretation if I may.. Firstly, the winds from a vector more northeast, not due north in my reading of it. Secondly, they are definitely not suggesting that high pressure will dominate the entire forecast period either with strong hints of a more cyclonic pattern becoming established in the latter part of the period. As I posted in the MOD thread, I think this is a blend of the ECMWF/GFS Operationals & the idea of a trough perhaps slipping in from the east around Day 7 to Day 8.. Again, I could be reading it wrong but that outlook certainly is a wintry one & indicates that high pressure will gradually transfer to the northwest. Of course it could all change again tomorrow! :winky:

I will agree that UKMO is a worry at T+144, but the Met Office seem to be rather confident & overall mean ensemble and deterministic guidance must be promising when you see a cold to very cold outlook with snow mentioned several times: To me, they favour a blend of the ECMWF/GFS Operational solutions:

This 06Z run is a thing of pure beauty... What would we have all given to see such synoptics during the past winters, at any time! For those who cherish cold and wintry synoptics, from T+120 onwards these runs are something to truly behold. Don't worry about the finer details... The main evolution is shaping up very well with the HP cell cut off by T+102 - Not deep in FI, but T+102 which is amazing. Snowfall will be a great bonus but to see these synoptics is simply fantasitc. Oh and did I mention that the Parallel run has widespread cold uppers across the British Isles @ T+132 http://www.meteociel...ode=1&runpara=1 This is simply astounding stuff guys, cherish these runs

GP, thanks again for this in-depth analysis. Your reasoned & supported posts are always a great source of both knowledge and learning for all on the forum. If & of course it's a big if, areas of low pressure do eventually approach from the southwest as advertised by the GFS suite several times, we could be looking at the potential for some significant snowfall with marginal situations etc..

Thanks for the heads up on this The Eagle It's hard to judge with the Icelandic charts really! The boundary lines seem to be rounded but I would suggest at least 850's of -10 at T+192, because the initial transition to the -15 boundary lines is well into SE England... It's always hard to tell from the Icelandic charts but if the scale is read from left to right then the previously mentioned values would be fairly alright. In fact, if you look at Meteociel, you can see that 850's of -6 to -7 are into Scotland by T+168 so again it's hard to tell... The Icelandic site is not very specific. http://www.meteociel...68&mode=0&map=0 EDIT: Thanks for the welcome back CH Indeed, as the Eagle was saying, it does look like +5 could be added to each value but it's hard to tell really & depends on what way forward the scale is read. Is there any other site that we can obtain the ECMWF 850's from in graphical form? SA

In relation to the 12Z ECMWF Guidance & the 850mb temperatures: T+168: -10's filtering into the East & Northeast: T+192: -10'S & - 15'S across the British Isles: T+216 Onwards: Cold pool remains across the British Isles & As the low sinks south - look at those -20's just to the East across the North Sea:

Initially yes it is timistry as Eire will be under more of an influence from the HP cell. However, the latter stages of the ECMWF 12Z evolution present opportunities for significant snowfall across Ireland also. With any northeasterly flow: Eastern, Northeastern & Southeastern parts of Ireland are most prone to snowfall. HOWEVER, you have a significant chance of frontal snowfall if a depression were to approach from the SW against very cold air already in place - this can give western and southwestern areas quite significant falls of snow & did so during some of the classic cold spells of the past.

Some might rubbish it but it's also been fairly consistent: JMA - Bitter Easterlies Across the British Isles Again, the pattern is set in stone almost at T+120, with the S-wave dropping down into Scandi & subsequent NW Retrogression. http://91.121.93.17/pics/Rjma1201.gif Cold air well into eastern areas by day 6: http://91.121.93.17/pics/Rjma1441.gif Day 7 has a snow event - very progressive: http://91.121.93.17/pics/Rjma1681.gif At Day 8 the British Isles is engulfed with snowfall: http://91.121.93.17/pics/Rjma1921.gif Either way, whatever the outcome in terms of cold & hopefully snowfall, we can now have increasing confidence that we are going to see a synoptic evolution not seen in mid December for some years. Fingers crossed!

IF T+240 were to verify, then a good chance that a large portion of the British Isles would be snowbound, pressure low enough for significant snowfall being widespread, getting even colder as the low sinks south. Past T+144 is irrelevant anyway, because the building blocks are already set in stone. There is still another T+24 hours before we can begin to be more certain, but there is now a strong chance of very cold air beginning to approach eastern areas by the end of this weekend.. Just hope and pray that the NWP cross model agreement continues, although no doubt there are more ups and downs to come yet! Fingers crossed because this could be epic!

STUNNING ECMWF @ T+168 We have waited years and years for an outcome like this & it's all in the reliable timeframe!!! This run & the others epitomise the hopes and dreams in terms of weather of many cold weather fans on here! I expect the media to be ramping this up very shortly if this agreement and consensus continues.

This is nerve shredding, I've never seen it so close to the wire! However ECMWF MUCH better this evening, retrogression clearly beginning at T+120, cold air filtering in at T+144 as the trough drops down through Scandi!