General Model Output Discussion Tuesday December 22Nd:

[Polar Continental]

The ecm 00z looks pretty severe to me for much of next week, especially in the north, sub zero temps and snow showers or more persistent snow with drifting IF those charts verified, just depends on your definition of severe really, even the somewhat toned down gfs looks wintry enough, equally wintry to what we are currently experiencing in my opinion.

Hi Frosty,

I was referring more to the GFS as regards, no severe cold, but I agree the ECM has does show great potential at around 192H.

If it continues to repeat these current projection for a couple more days, then some very interesting times ahead.

[Guest North Sea Snow Convection]

As the cold spell is effectively over here, I am very much pinning my hopes on this mornings ECM. It doesn't have the agreement of the GFS or GEM and is in FI though.

However, the fundamentals do give some support to such a reload, and it is also very encouraging that the ECM operational is solidly backed by its ensembles.

Fingers crossed for that one.

[mountain shadow]

As the cold spell is effectively over here, I am very much pinning my hopes on this mornings ECM. It doesn't have the agreement of the GFS or GEM and is in FI though.

However, the fundamentals do give some support to such a reload, and it is also very encouraging that the ECM operational is solidly backed by its ensembles.

Fingers crossed for that one.

GFS 6z is very similar to ECM at T+120. Cold air gathering to the North.

http://209.197.11.119/c9s4a5k3/cds/gfsimages/gfs.20091223/06/120/h500slp.png?dopvhost=charts.netweather.tv&doppl=841a626ccf2b8d48cf7b8d181ebe8647cf7b8df4&dopsig=a0161121ae0424dcc77898a09f2175ad

[mcweather]

As a veteran of many of the cold and snowy winters fduring the 60's 70's and 80's. I have to say that the current set up reminds me very much of the winter of 1978/79. We even have the possible prospect of a new year blizzard just like we had back then.

Very interesting times ahead I think.

[beng]

As the cold spell is effectively over here, I am very much pinning my hopes on this mornings ECM. It doesn't have the agreement of the GFS or GEM and is in FI though.

However, the fundamentals do give some support to such a reload, and it is also very encouraging that the ECM operational is solidly backed by its ensembles.

Fingers crossed for that one.

Yes I agree - cold reload looks very likely. ECM looks to back the ideas that Glacier Point has been musing over in the technical thread - namely a new High pressure cell developing around Southern Greenland/Iceland (ties in nicely with the current MJO too). GFS I think is possibly struggling with its normal model bias of tending to overdelop low pressure systems at the 144 hour range - i.e. the one off the US Eastern sea board, and probably it's too deep with the low to the SW of the UK (if so, it's likely to be modelled slightly further South as we get closer).

Edited December 23, 2009 by beng

[mountain shadow]

GFS 6z folds to the ECM 0z with a 'proper' northerly.

http://209.197.11.134/c9s4a5k3/cds/gfsimages/gfs.20091223/06/216/h850t850eu.png?dopvhost=charts.netweather.tv&doppl=841a626ccf2b91c7cf7b91971ebe9adccf7b9172&dopsig=685a75820b5d2a450f617721f84ba88b

http://209.197.11.130/c9s4a5k3/cds/gfsimages/gfs.20091223/06/240/h850t850eu.png?dopvhost=charts.netweather.tv&doppl=841a626ccf2b91a7cf7b91f71ebe9aa8cf7b9102&dopsig=2316094ce967c61bf3d865db8f587440

Ties in with GP's thoughts.

This is some winter.

[TEITS]

Well an incredible 06Z run. I don't think i've ever seen so much green around the pole.

I shall be curious to see what the AO/NAO ensembles say later.

[mountain shadow]

Well an incredible 06Z run. I don't think i've ever seen so much green around the pole.

I shall be curious to see what the AO/NAO ensembles say later.

Of the scale I would think. This cold spell will soon turn into a cold period. Amazing stuff.

[Guest North Sea Snow Convection]

Yes, and now the GFS 06z has moved very close to the ECM 0z.

MS - as you say, that was becoming apparent from around t120

It does indeed tie in perfectly with GP's ideas.

No point worrying about the detail with each output at this range, as that will always chop and change - but a regrouping of that Greenland ridge and lows tracking as far south as possible is what we want to keep seeing in terms of the trend.

Beng -I agree that GFS will inevitably make a meal of the low pressure systems at this range too - part of the detail that should be ignored at this stage in terms of intensity and exact track etc.

Reading across the rounds - there does appear to be some consensus that the AO is going to stay significantly suppressed into January. The longer this phasing digs in then the more likely a feedback will be set up - especially as we get into January and the NAO and the AO start to correlate very closely, with wavelengths changing. So this upcoming period is crucial in that respect too, in terms of the extended outlook beyond the New Year itself.

An SSW would be the icing on the cake now!

Edited December 23, 2009 by North Sea Snow Convection

[Nick B]

No they were the 0Z. You need to refresh the page probably.

Hmm. I should be about 15 miles from De Bilt during that peak snowfall time from Monday to the Friday, if we can actually fly out! I'll let you know if it verifies there!

[geoffw]

sorry about this one liner but by looking at the models GP has been entirely correct. It seems like I was worrying over nothing. how fantastic it will be to experience a winter like the 80's!

[SMU]

Well an incredible 06Z run. I don't think i've ever seen so much green around the pole.

I shall be curious to see what the AO/NAO ensembles say later.

without looking at the ao ensembles- I would say a brief rise from the very rare -4 s.d to perhaps -1/-2 then another plunge southwards...

Theres only a handful of winters in the archive history that have seen such negative AO/ NAO modes - if this one lands as progged by todays models you can choose Jans CET from a handful of Archived CET's---- jan 47, jan63, feb 79, feb 86, dec 81 being the handful.....

The caveat here though is in the recent past- circa ~ 5-7 years everytime the ECM has progged this evolution at day 7-10 the eventual outcome is a toppling mid atlantic high pressure-

I suppose support then from either corner- I guess based on the last 7 days you would have to say theres the best chance ever of the cut off high developing.....

exciting times & *IF* it goes the way of cold then this will be the best cold period for some time- & aggregate over 4 weeks would 100% deliver a below 0c CET - maybe even a Jan 0c CET that would be nice.......

Steve

[cooling climate]

Absolutely terrific run. As I said earlier to me its all about the vortex to the north pushing across the north of

Greenland and then down into n/Canada so that our ridge in the Atlantic can ridge further north aided by the

heights over the pole and n/w Russia to build a true block again in the Greenland area.

Where will this run lie in the ensembles I wonder.

[kold weather]

The 06z GFS is very good, I just looked at the 0z GFS and thought how amazingly progressive it was with regards to flattening the entire pattern...the 06z GFS and the ECM idea seems more likely. The opnly way we are going to see a way out of this pattern is a big rise in the AO and the regrouping of the PV. If this doesn't happen then given the state of other teleconnections I see no real reason why there should be any real modification in the general pattern.

With a southerly jet, such a pattern could become a very long lasting one...rather akin to some of the more severe winters of the past. Of course I won't go to that extreme just yet but I suspect this will be the coldest spell in the north in the last two decades, beating December 2001 up there which I believe which was very good in general in the north.

Big snowfall prospects for the Midlands northwards at times, very cold in the north as well...less cold and very wet in the south till the turn of the year I'd have thought.

Steve, yep I agree, to be honest I suspect given we are already in a pretty impressive -ve AO there is every chance the ECm is right, in fact I'd say its the most likely option!

Quite amazing that we are finally looking at a real old school cold spell, I think if we do get a reload then a 30 day mean below say 1.5C is quite probable, maybe lower...

Edited December 23, 2009 by kold weather

[azores92]

im not getting too carried away with the models at this stage, only because the midlands havent done particularly well at all this time round after looking at snowmaggedon charts a couple of weeks ago, and more often than not things change dramatically within that fickle 72/96 hour timeframe, after seeing blizzards and the like being shown on the models time and time again. if we are looking at the same scenario in a weeks time, with those snowstorms still being forecast, i will take more interest in them. however, it has to be said, this is far from your average joe winter at the moment, and for many parts of the uk, there has been significant disruption and snowfall a plenty, away from a few spots(w midlands for one), and after 4 or 5 days of mildness, it could very well be back to similar scenes this week.

[Guest North Sea Snow Convection]

Absolutely terrific run. As I said earlier to me its all about the vortex to the north pushing across the north of

Greenland and then down into n/Canada so that our ridge in the Atlantic can ridge further north aided by the

heights over the pole and n/w Russia to build a true block again in the Greenland area.

Where will this run lie in the ensembles I wonder.

It's interesting that the ECM was initially programming an atlantic ridge yesterday, and the GFS over the last day or so has indicated a toppling ridge on some of its output as the longwave trough drops east into Scandinavia. Both models have now upgraded this today to a more substantial block near southern Greenland.

We have been here before with the models, showing such ridges around 7 days or so and then flattering to deceive, but this time we are underpinned by the solidly -AO, the vortex still disrupted thanks to negative zonal anomalies remaining in the lower stratosphere and also because we have cold air still very close by, irrespective of the slight departure northwards across the UK that is starting today. The NH hemisphere snow cover in general is as good as we have seen it in a long time, and this is condusive for a cold feedback too.

In view of all this, and the other background signals that GP has discussed, then the chances of the proper reload surely have to be higher than we have seen in recent years?

Edited December 23, 2009 by North Sea Snow Convection

[kold weather]

I suspect NCS the models were too progressive in lifting the AO and they are starting to respond to the fact it won't be quite so quick to raise up and the PV should stay seperate, thats really key and as long as we keep that in place I see no reason why a reload won't occur.

Certainly turning into a very interesting winter!

[Rollo]

Hi Tamara-I think the problem with constantly watching the winter charts over the years and being let down is that when we finally arrive in the situation like this we cannot believe our eyes and look for anything that could go wrong,to be honest I suppose there are but with all the current background signals perhaps we should be considerably more confident this time around.

[Guest North Sea Snow Convection]

Hi Tamara-I think the problem with constantly watching the winter charts over the years and being let down is that when we finally arrive in the situation like this we cannot believe our eyes and look for anything that could go wrong,to be honest I suppose there are but with all the current background signals perhaps we should be considerably more confident this time around.

Hi - yes I said yesterday that it is almost like expecting an inevitable hang over after the party. I'm not sure that if you add all the current indicators up, that there are any recent analogues for this winter. I'm quite sure that the solar min has a big say in all this. Quite significant how last winter was colder than expected, and thus far, this one is trying to surpass it....

[Methuselah]

Agreed Tamara.

Another difference this year, is that a cold pattern is progged to evolve from an already cold pattern? IMO, unlike most of the recent winter situations - we already have most (if not all) of the ingredients already in place...Judging from (straw clutching) last summer's self-reloading patterns, it's always easier for the existing situation to remain, than for an entirely new one to develop? Inertia anyone?

That said, today's 06Z can only be described by that esoterically scientific term: a stonker!!

[03jtrickey]

Very interesting ensembles from the 6Z

Gloucestershire:

Very strong support for another cold plunge around 30th Dec / 1st Jan. There are only two runs that keep 850s above -5 at that time, but these runs both end up in a cold solution. Op is one of the coldest runs but it is not an outlier and not without support.

I think the MetOffice may have been hinting at this yesterday, when they mentioned snow falling to "progressively lower levels" around the New Year in the 15 day forecast. It will be interesting to see their take on things this afternoon.

[Optimus Prime]

I'm surprised there is little talk on that stonking low for tueday and wednesday, that could really bring some very severe weather, extreme snowfalls for midlands and north england and extreme flooding for the far south maybe? also freezing rain or am i wrong?

I think that's a fair assumption. For highland areas of the north some high snow fall totals but not much to lower levels;

Milder sector pulling up from the south...

[ronant]

Well fantastic models for the north and it looks like staying cold for some time, but, for the south it looks like turner slightly milder today and i cant see it being cold enough for snow for quite a while, looks like next week will simply be quite wet.

Edited December 23, 2009 by ronant

[Thundery wintry showers]

I am not confident about duration but I am now, on the basis of today's and yesterday's runs, fairly confident that we will get another Arctic outbreak towards the end of December, infiltrating to Scotland and northern England by around the 29th, and eventually heading "down south". The duration, especially in the south, depends on how quickly high pressure can "sink" from the NW and how far south the post-Christmas low tracks.

I thought we were going to have to look east for most of our cold outbreaks this winter, especially after the setup that evolved midmonth with the area of exceptional cold heading out of Siberia. At present, though, it seems that we're mainly looking north, which has surprised me, but with plenty of cold air up there to tap into it's not a big issue. The advantage of the current regime for snow lovers is that whereas many "easterly" types are cold but dry (and of course the same goes for patterns that give rise to northerly topplers), this particular version of the "northerly" type, with blocking to the NW and southerly tracking polar front, tends to be cold and wet.

[Tom Montalbano]

Quite a few posts are commenting on this spell of weather having similarities to the winters of 78/79 and 80/81.

IF we have a reload sweeping right through the UK it looks to me a sort of hybrid between late Dec.78 and early Jan.82.

DEC.78

http://www.wetterzentrale.de/pics/archive/ra/1978/Rrea00119781229.gif

http://www.wetterzentrale.de/pics/archive/ra/1978/Rrea00119781231.gif

http://www.wetterzentrale.de/pics/archive/ra/1979/Rrea00119790101.gif

JAN.82

http://www.wetterzentrale.de/pics/archive/ra/1982/Rrea00119820104.gif

http://www.wetterzentrale.de/pics/archive/ra/1982/Rrea00119820105.gif

http://www.wetterzentrale.de/pics/archive/ra/1982/Rrea00119820106.gif

The current models show a stronger northerly flow to follow of course.

Certainly fascinating model watching ahead and the current cold spell for my area is the best pre-Xmas event since 1981.

Regards,

Tom.