General Model Output Discussion

[Damp and dreary]

Merry chrimbo all.

Can i just add with reference to the will it get warmer from the south or not, that it has already been substantialy milder here on the south coast, 5c yesterday and already 4.9c right now. Personaly im waiting/hoping for things to start to pick up in a weeks time with a poss colder push again.

Edited December 22, 2009 by jasonuk

[tinybill]

morning all i know its f1 fantasy land but i think its the first time i seen cold from the easten sea board come al the way over to us

[nick sussex]

Far too much chopping and changing from the models for me to have any faith in them at the moment. Even tomorrow we have disagreement with the GFS indicating a spell of rain moving NE whereas the Met O only talk about a few showers. The BBC forecast for my region suggests it will remain cold, dry with temps only around 2C on Xmas day.

After xmas and who knows. Will the cold air be able to push from the N before the LP system in the Atlantic moves in? What track will this LP eventually take?

At the moment I think a fair summary is turning less cold especially in the S/SW. However possibly turning colder once again from the N between Xmas and New Year.

Hi Dave

Yes looking at the gfs 06hrs run its looking to remain cold in the north and a possible snow event if the low to the sw can stay to the south of the UK. The key here is we don't see phasing of the low sitting over the uk and the system coming in from the sw. In a nutshell then systems phase this would take longer to get back to cold, no phasing then could be a quick return to colder and wintry conditions.

[Nights King]

I am interested to know what is going on with thursday evening? The meto is very vague and forecast sugests a few light rain showers but could this turn to snow over the hills and high spots in the west country like yesterdays patchy snow?

Difference with only a few miles is quite large! here away from the coast it is still -2.5c with complete snow cover.

[stratty]

morning all i know its f1 fantasy land but i think its the first time i seen cold from the easten sea board come al the way over to us

Not sure you are reading that chart correctly Tractor Boy?!

That shows milder conditions!

Edited December 22, 2009 by stratty

[TEITS]

Just to show the uncertainity but the 06Z even suggests a white xmas for some of us.

So whilst there is uncertainity with regards to the general pattern after Xmas. We also have uncertainity with regards to the details this week.

[snowmadchrisuk]

Morning , my thoughts are Christmas eve will be rain South of Northern England . and on this setup 26th-29th I don't buy +2 , +3 850's in London and -5 in the East Midlands . I do however think there is a strong possibility of a reload from the North , North East at the beginning of January due to the signals supporting continued Northern Blocking.

Chris

[TEITS]

This is spooky as its exactly the same date as the famous blizzard of 1978.

http://www.wetterzentrale.de/pics/Rtavn2161.png

Fair enough it isn't as impressive but you get my drift.

[Cal]

Last couple of runs the GFS has trended this scenario. Think it was last nights 18hrs run and now.

http://91.121.94.83/modeles/gfs/run/gfsnh-0-204.png?6

One major snowstorm if that comes of! Longshot but worth keeping an eye on.

[Methuselah]

Regarding the models, as others have said - a lot of uncertainty exists beyond the xmas period. A critical period in many respects for the direction that weather patterns take after the New Year

Hope that all others on here have a very enjoyable xmas. Dare I use a after that

Sometimes, Tamara, whatever you do, you simply cannot win...

Anyhoo, as you say, all is very-much still up-in-the-air regarding the post-Chrimbo period...And have a good one, yourself...

[stratty]

..............excellent 06 from GFS for continuing the cold - full of exciting potential

[Iceberg]

Looking at the 240 range again in FI at general trends the models seem to break out some severe cold (support by the 06Z) as an air mass moves out of the Ural up and over the North pole to end up near n.Greenland (1000-500 thicknesses of 470 (almost record breaking), on some charts 500 temps down to -55C are evident.)

This will IMO be a critical component from the 1st of Jan onwards for good or bad.

[Frosty.]

..............excellent 06 from GFS for continuing the cold - full of exciting potential :lol:

The 6z has the potential to produce even more snow than some of us have seen during the last 5 days, it could all change though because there is a lot of model confusion in the T+72 range so if they can't even nail that yet, it will make a mockery of the longer range but i'm delighted with the trend from the ecm & gfs with a potential major wintry reload in FI.

Edited December 22, 2009 by Frosty039

[cooling climate]

Plenty to be optimistic about if the 06z GFS run is anything to go by with only a temporary recovery

of temperatures in the south.

Looking at the n/hemisphere charts the 06z run builds another +pna ridge over western America

this is almost certainly a signal from the enso regions of another kelvin wave moving east towards

the date line.

Whether the model is being a little progressive with this remains to be seen.

Certainly encouraging signs again this morning from the GFS at least and if it was not for this exceptional

spell of wintry weather that the majority of the country has been in these last five of six days then I

think we would take the 06z run this morning with open arms.

[Guest North Sea Snow Convection]

Sometimes, Tamara, whatever you do, you simply cannot win...

Anyhoo, as you say, all is very-much still up-in-the-air regarding the post-Chrimbo period...And have a good one, yourself...

Thanks Pete - you too (christmas smiling face)

It has been a very nice change that we have the mild air in the uncertain FI time period and the cold air in residence. Hopefully that is the default pattern for the winter.

January will see a closer link up between the AO and NAO - so it will be very important in terms of where the pattern goes following this cold spell

The models are trying to hint at an eventual 'lift out' of the -NAO pattern as the year closes and it is a case of a) will this actually happen and :lol: if it does, how will the patterns reconcile in terms of how much the AO might move upwards from its very negative position with an associated northward move of the jet stream?

This is where the signals need to reload in terms of generating a further swathe of northern blocking without zonal winds over the pole gathering too much momentum and letting the advantage swing away from the cold dominated set-up we have been in. IMO we wait to see those signals hopefully appear asap, as the above indicators, as said, correlate much more closely during the heart of winter.

[Methuselah]

Thanks Pete - you too (christmas smiling face)

It has been a very nice change that we have the mild air in the uncertain FI time period and the cold air in residence. Hopefully that is the default pattern for the winter.

January will see a closer link up between the AO and NAO - so it will be very important in terms of where the pattern goes following this cold spell

The models are trying to hint at an eventual 'lift out' of the -NAO pattern as the year closes and it is a case of a) will this actually happen and B) if it does, how will the patterns reconcile in terms of how much the AO might move upwards from its very negative position with an associated northward move of the jet stream?

This is where the signals need to reload in terms of generating a further swathe of northern blocking without zonal winds over the pole gathering too much momentum and letting the advantage swing away from the cold dominated set-up we have been in. IMO we wait to see those signals hopefully appear asap, as the above indicators, as said, correlate much more closely during the heart of winter.

Thanks, T...

I think that you've summed things up pretty well, there...It's all so reminiscent of the winters of the late '60s, IMO: rain, sleet, snow and freezing fog??? Will it, or won't it? That is the question...

And, some of you suggested that this situation might arise this time...So, hats off to you!

[03jtrickey]

Quite a cluster of cold ens members from the 1st Jan onwards

http://charts.netweather.tv/ensimages/ens.20091222/06/t850Gloucestershire.png

[MKN]

Just to show the uncertainity but the 06Z even suggests a white xmas for some of us.

So whilst there is uncertainity with regards to the general pattern after Xmas. We also have uncertainity with regards to the details this week.

Thats the actual precip for that time, suprised you posted that teits as you should know its always miles out. The precip chart gives a better indication of any ppn.

[Tom D]

Quite a cluster of cold ens members from the 1st Jan onwards

http://charts.netweather.tv/ensimages/ens.20091222/06/t850Gloucestershire.png

Interesting to see the operational is now one of the coldest in the last couple of days of 2009, and after this much colder, more along the same lines as the control was yesterday and is today.

Also interesting to note it seems very unlikely the cold will leave the north,

http://charts.netweather.tv/ensimages/ens.20091222/06/t850Aberdeenshire.png

But leaves the south before returning,

http://charts.netweather.tv/ensimages/ens.20091222/06/t850Hertfordshire.png

[snowmadchrisuk]

If you take a look at the stats , you can see overall this week the UKMO and the GFS 00z have been the best models this week.

As this has been an unusual situation for early December then maybe these will be the models to look to for any further cold coming our way .

http://www.emc.ncep.noaa.gov/gmb/STATS/html/graphics/acz6.gif

[Glacier Point]

Some very solid signals out there that the longwave trough is going to drift across the UK and drop into Scandinavia over the extended forecast period with GFS, GEM ensemble mean and operational (I assume also ensemble mean) all pointing towards this as we hit January.

This is tied into another complex blocking structure forming over southern Greenland. The shape of the polar vortex (very much elongated) should assist with this pattern, dropping a lot of cold air into western Russia and Scandinavia and across the central Plains in North America.

GFS and GEM ensemble mean height anomalies for days 11-15 tie in well with last night's CPC forecast:

http://raleighwx.easternuswx.com/models/gfsensemble/00zENS11-15day500mbHeightAnomalyNH.gif

http://raleighwx.easternuswx.com/models/cmcensemble/00zGGEMEnsembles500mbHeightAnomalyNH360.gif

Model of the moment looks to the the GEM.

Temperatures don't look like rising above average for any prolonged period, typically 1-2 below average for the time of year.

[SNOW-MAN2006]

OMG! Look at this mornings charts... STUNNING!!!! The GFS has certainly been hinting at a cold horizon again, and now its suggesting the cold never really leaves us, the 6z run never lets temperatures from the midlands north ever get above 5 degrees. This is a stunning run with lots of snow potential for sure! Im glad i bought a new hat scarf and glove set yesterday, judging by these charts its guna be money well spent.... maybe people should start investing in snow ploughs for the front of their cars lol (sorry mods had to fit in a ramp somewhere )

As for xmas snow.... some snow into morning xmas eve looking likely topping up snow amounts for some... with a few snow showers hugging the coasts overnight... but the greatest chance of snow on xmas looks for southern scotland and northern england as a band of rain/sleet/snow runs into the cold air over these regions in the evening, will be quite nice if this verifies, sitting with my beer watching a xmas film with snow falling outside... ahh if only

[Thundery wintry showers]

Good news for those after a white Christmas. The GFS has backed away from its deepening-up of that southerly tracking low that, on yesterday's 12Z and 18Z runs, introduced some wrong-side-of-marginal air into the south, Midlands and north-east England. Instead, we have a trough to the north of the main system bringing its own area of precipitation north-eastwards across much of England and Wales. This looks marginal as well- but not as marginal as the stuff from the main low to the south, and many places, especially high ground, could see a snow cover from it, particularly in the north of England.

So we keep the cold and we keep the precipitation. In a marginal setup like this there remains the chance of some areas seeing a thaw of existing snow cover but that's a risk that we're going to have to take, as all models are agreed that precipitation will affect most areas in some way or another on Christmas Eve. Christmas Day continues to look dry, cold & sunny with some coastal snow showers but there is a system to watch coming in from the west during the afternoon. It may well turn to snow on its forward flank which would give many places a technical "white Christmas" with snow falling on the big day.

The (temporary) breakdown to milder weather is then perfectly timed, holding off until Boxing Day.

Edited December 22, 2009 by Thundery wintry showers

[TEITS]

IMO the above chart posted by TEITS over does the chances of Xmas Day snow by some degree. Whether this is down to the cold surface temps confusing the issue somewhat I'm not sure, but for my money the chances of any of the white stuff on the big day continues to fade, at least away from Scotland and hillier parts of N England and N Wales.

I disagree.

Pretty good agreement on the ensembles that its going to be pretty cold on Xmas day with the mean around -4/5C in most areas away from the SW/extreme S. Now aslong as precip is around then the chances of seeing the odd snowflake remain.

Don't forget conditions yesterday didn't suggest snow would fall in London but it did!

Still doesn't matter anyway because I shall have a white xmas even if it doesn't snow. I prefer to have snow on the ground with sunshine than having the odd snow flake mixed with rain.

P.S the N,ly that you thought wouldn't deliver has certainly delivered to many locations!!

[MR EXTREMES]

id like to ask you talk of cold in the northern half of the uk models suggesting cold here,

but the southern half of england and eastern parts sure for there to be cold here makes winter classic from 1 snow event.

or is it just the north that matters i get the feeling we are out numbered and very few people bother to post from this half of the uk whether that be through lack of knowlage of the models or other reasons.

yes maybe i am stamping my feet lol.

but from what i can see is models pointing always to northern area for events when southern areas get 1 event and thats it,

and i can say for cert if the warmth where having here today was to extend north then hopes riding on the models will be dashed.

to be honest its hardly 1979 or any other year in the last 5 decades its not classic at all infact i think its less impessive as last year where although dryer it was cold and prolonged.

its very difficult how anyone can really suggest this cold getting colder heading through into january there all fi and very messy,

ok perhapes its easier to see what you wish for but this is not reality from what i can see.:winky:

Edited December 22, 2009 by badboy657