Model Output Discussion

[Altostratus]

Looks like a upgrade in the short term. Need an injection of cold air from the NE to maintain the cold spell though. It certainly looks possible but will it happen...

[A.J]

up to T+117 now, -10c 850's covering most of Central & southern England...So far, so good

[snowking]

With that 528 dam in on Sunday , the Current forecast would be Showers turning increasingly wintry with a covering likely over night for inland areas East of Birmingham.

Thats a very specific forecast!

Run looks a couple of degrees cooler on all counts, but also drier than the 6z

For eastern coastal counties I'd think chances are good for some snow showers from this run....further inland we might struggle to get too many, though hopefully given anomalous warmth in the N. Sea convection would kick off

SK

[John Cox]

At t132 looking like a much better run for us here in Ireland, keeping the low a little further south and the airflow has a better NE flow which should keep temperatures a little lower.

[Iceberg]

Very good southerly undercut on this run, at 132Z keeping the southerly LP's away, to allow us to concentrate on the snow event coming from the NE.

[mountain shadow]

An honour to see charts like this at 5 days away.

http://209.197.11.95/c9s4a5k3/cds/gfsimages/gfs.20091210/12/120/airpressure.png?dopvhost=charts.netweather.tv&doppl=841a626ccf3b7dc0&dopsig=049ec843e581ce457f0e4e64be766c32

Slighter warmer air in the on coming northerly though.

[Kiwi]

Looks like a upgrade in the short term. Need an injection of cold air from the NE to maintain the cold spell though. It certainly looks possible but will it happen...

Hoping that the low over Finland at T+126 will start to inject that colder air from the NE

[Neilsouth]

http://91.121.94.83/modeles/gfs/run/gfs-0-138.png?12

Much better run for the south so far - colder and still from the ne/east

[Altostratus]

Stunning chart:

http://www.wetterzentrale.de/pics/Rtavn1441.png

That will take some shifting.

Edit: Not enough forcing to advect the coldest air towards us, but nonetheless, synoptically fascinating. It isn't difficult to envisage subtle changes to the development and alignment of that low to the SW to have a huge impact on us. My hunch is that GFS is probably over doing it.

Edited December 10, 2009 by Altostratus

[Guest North Sea Snow Convection]

GFS 12z providing my idealist set-up - NSSC!

This scenario as TWS has just said has gained in momentum since appearing over the last few outputs - which is very encouraging as it is coming more and more towards a pretty reliable timeframe. Just the first t72 frame on the ECM 12z tonight will be very illuminating to see if we have good model consensus for this convective easterly (assuming the UKMO is in line still too of course). Fingers crossed!

These are dream charts!!

Edited December 10, 2009 by North Sea Snow Convection

[Neilsouth]

http://91.121.94.83/modeles/gfs/run/gfs-0-144.png?6

Lovely for all ,a truelly fantastic 12Z gfs !

[Eugene]

Don't worry about less cold air moving southwards it will stay pretty cold before the next shot even 1962/63 had less cold air at times, this run looks like being not as good for snow lovers after wed but for me its an improvement because the other scenario of LP pushing north is too risky for my prolonged cold spell

[Snow Queen one]

On +144 that low to the south west of the BI is it going to hinder or help us it is very tight compared to the 06z

[Lewis]

This run is just too marginal for many coastal areas, even areas a good 15 miles inland, not much precipitation about either (although they will be a fair few showers for coastal areas) which will be a waste as they will mainly fall as sleet,rain,wet snow even during tuesday.

Lewis

[Geordiesnow]

The first easterly still looks decent enough although it must be noted that when the coldest air does arrive, the PPN tends to fade, i assume because the high was a bit stronger and closer to us consequently limiting the showery activity.

Regarding the 2nd possible easterly, the flow is slacker and the high is a bit too close to us, consequently limited showery activity and not as cold i would of thought. Not too fussed about this as of yet as i want the first easterly to happen first.

[SNOW-MAN2006]

GFS 12z Cold Spell Watch

T36 HRS

Cool Evening Across the UK as 0 850's spread from the east. Minus Dewpoints from Midlands north indicating the possibilty of a frost forming (bar the coasts) ... A very nice clear night but wrap up warm. Low Winds bar the west of ireland as isobars tighten at the western edge of the high as it bumps up against the low pressure sitting off the coast of northern canada.

http://209.197.11.111/c9s4a5k3/cds/gfsimages/gfs.20091210/12/36/h850t850eu.png?dopvhost=charts.netweather.tv&doppl=0bb0626740917b7c40c17b2c9104706740c17be4&dopsig=523db85fdf0e205a1a97184a8942999c

T60 SUNDAY 0:00 HRS

-5 850's coming in from the SE Corner. Again frost risk posed for spine of the country. Some light showers getting into the Far SE Corner, whilst 850's seem low enough for snow Ground level temps still dont support such wintryness. Only getting as far as from the river severn to probabily nottingham (if ya draw a line) then receeding again.

http://209.197.11.95/c9s4a5k3/cds/gfsimages/gfs.20091210/12/60/h850t850eu.png?dopvhost=charts.netweather.tv&doppl=0bb062674091781a&dopsig=2046b022338f9b23863aca5ce3f3ef79

T-87 MONDAY 3:00 HRS

The -5 850's head back in with -10's coming across france, germany and poland. Dewpoints close to but not below zero so snow may well be limited unlike what the GFS Percip charts are showing.

http://209.197.11.110/c9s4a5k3/cds/gfsimages/gfs.20091210/12/87/h850t850eu.png?dopvhost=charts.netweather.tv&doppl=0bb0626740917edc40c17e8c910475c740c17e45&dopsig=5200d0b5a8b7eb831ffa9165008fd691

T-99 MONDAY 15:00 HRS

-5s now spreads across entire UK. -8s getting into SE Corner and -10s Bordering the Kent Coast. HP Eye sat nicely to our NE pulling in some fresh easterly winds. GFS Percip charts showing snow falling quite widley but actual percip charts show heavy showers for East Midlands Yorkshire down to the SE with a few showers for NE england Coast. All of which have the potential to be wintry but more likely the further SE you travel. Sea breeze helping coastlines to stay to 4/5 degrees making things very very marginal here at the least.

http://209.197.11.107/c9s4a5k3/cds/gfsimages/gfs.20091210/12/99/h850t850eu.png?dopvhost=charts.netweather.tv&doppl=0bb0626740917f1d40c17f4d9104740640c17f79&dopsig=fa2726a0bd4867ee691bffea6dff7148

T-114 TUESDAY 06:00 HRS

A light band of showers heading north west wards during the night it would seem to give those inland and high up a nice morning dusting, *POSSIBILTY* ONLY! Dew points and temps fall away behind this band as skies tend to clear. Some light showers flirting with the south coast again likely to be wintry if they get inland and less coastal warming here so boundaries will be far less. Airfeed now a component of the arctic and Siberia.

http://209.197.11.95/c9s4a5k3/cds/gfsimages/gfs.20091210/12/111/ukprec.png?dopvhost=charts.netweather.tv&doppl=0bb0626740917ca0&dopsig=6574aff48baf35fb8245f37a5cb48bea

Thats the story so far in terms of the GFS.... Wednesday night sees heavy showers for the east but quite warm here maybe reaching a 7 or 8 by wednesday morning... :/ The Cold air is coming...arriving in scotland north by midday wednesday then presumabley south, awaiting T147.... it is also to be noted the cold air being prevelant over the south in the shorter term... but i would say this event is still marginal for coastal areas in the south, the north will get their turn later in the week is how its looking...

Will update when the run is finished....

SNOW-MAN2006

[snowmadchrisuk]

Thats a very specific forecast!

Run looks a couple of degrees cooler on all counts, but also drier than the 6z

For eastern coastal counties I'd think chances are good for some snow showers from this run....further inland we might struggle to get too many, though hopefully given anomalous warmth in the N. Sea convection would kick off

SK

They never get ppn forecasts right this far out , it is actually a much wetter/snowier run for Sunday/Monday. Showers will be about in the East for most of the week I expect. The direction of the flow is what is important to look at as this effects who get's ppn and who doesn't.

[kold weather]

The 12z shows the utter perfect wind angle for a thames snow streamer, the models nearly always miss this bar the very high resolution onesbut if a wind angle sums up a streamer, it'd be the GFS for Monday night through to Tuesday....

Anyway the 12z is very different from the 06z thats for sure, there isn't a shortwave at all on the 12z!

[weather eater]

I think people are looking to far ahead for snow prospects, as subtle differences are making quite a difference even at close range. From Tuesday on shortwaves are being handled quite differently on this run from the 06z.

[kold weather]

Don't expect a great FI from this one, looks like heights are sinking back southwards again, AKA 0z ECM...the best hope we will have on this run will be a northerly reload but we shall see...big step backwards may well be occuring....

[Methuselah]

I would like see that 'warm' sector get narrower as it moves south??? Plenty of time for shrinkage... :unsure:

[John Snow]

pleased with the 12z from a purely selfish point of view, yesterday I had given up any hope but now I am confident of at least a dusting, hopefully further upgrades in coming days

[Iceberg]

Similaritys between GFS and ECM from 144Z to 180Z. Lack of Shortwave(at least for us) as you say KW.

It will be interesting to see what this comes too, long term cold and snow the weekend after would be my guess.

[reef]

This run is just too marginal for many coastal areas, even areas a good 15 miles inland, not much precipitation about either (although they will be a fair few showers for coastal areas) which will be a waste as they will mainly fall as sleet,rain,wet snow even during tuesday.

Lewis

The initial easterly blast isnt great for us up here, but for anywhere south of the M62 corridor, even coastal areas should be ok as 850hPa temperatures are lower than -8C and dewpoints remain below freezing:

Id expect some snow showers for East Anglia even out to the coast, but a wintry mix further North. The flow is quite slack too, so its difficult to say if they will get far inland.

[mountain shadow]

This chart is impossible surely?, I have never in my life seen an Atlantic block like that.

http://209.197.11.95/c9s4a5k3/cds/gfsimages/gfs.20091210/12/174/h500slp.png?dopvhost=charts.netweather.tv&doppl=841a626ccf3b41b6&dopsig=0d44012e35516c6aff22978e4c37a449

It fits in with the Meto Update though for eastern areas to get the most snow.