Model Output Discussion

[shuggee]

GFS is the first of the 12Z outputs starting to come out right now. So please do carry on here with your observations and discussions regarding the various model outputs.

There's lots of other threads too remember:

Cold spell chat:

http://forum.netweather.tv/topic/58072-cold-spell-discussion-5/

Probability of a white Xmas:

http://forum.netweather.tv/topic/56704-white-christmas-2009/

And here to have a good old fashioned ramp:

http://forum.netweather.tv/topic/57891-ramping-thread/

If your post gets removed it might have been moved into one of the above threads

[kold weather]

Got to agree with GP, does look like it could be a long lasting pattern as ther eisn't much to enforce the changes...even when the AO/NAO does finally ease off a little bit with a southerly jet I'd have thought it'll be very hard to get rid of the cold, however the Uk, esp the south could well get some milder air in this set-up, its something thats very borderline. Equally though we could see a very snowy set-up as well, very interesting to watch what happens with the 12z, would be nice to see the 12z ECM come inline.

[cooling climate]

One of the things that I noticed on the 06z operational and parallel runs was

the low coming down from the Arctic is further east and with lower pressure

under the s/e quadrant of the high it forces the high to elongate bringing in

the much colder air to uk sooner rather than later.

Hopefully this will be repeated in the 12z coming out now and also in the Euro's

later.

[Neilsouth]

http://www.wetterzentrale.de/pics/Rtavn241.png

We are go for the 12z , looks to be stretched a little further east for this high

[Iceberg]

Looks good and a little colder for Sunday/Monday, with the snow showers slightly further south.

[Altostratus]

A cold spell is nailed now. The worst case would be cold frosty nights with no precipitation at all due to the high pressure taking residence over the BI and slowly sinking back into Europe. The best case would be the Arctic high exerting a bigger influence with a scandi trough forcing through with fully undercutting lows to the south – much like some of the charts showed yesterday and the day before were showing. Somewhere between these two extremes is looking most likely at present, with northern and eastern areas receiving at least some snow. It has to be said, this is slightly disappointing given the potential, but at least it won’t be mild – Mr Bett will probably have the week off. We could really do with undercutting in this run, much like in the previous parallel run

[Neilsouth]

In the end it made no difference as the charts are now back a similar output to 48 hrs

http://www.wetterzentrale.de/pics/Rtavn482.png

lets see if the rest is normal as in good lol

http://www.wzkarten.de/pics/Rtavn542.png

-5C uppers now make landfall on Saturday afternoon.

http://www.wetterzentrale.de/pics/Rtavn661.png

GFS keeps its consistent trend up

Sleet showers coming in sunday night across the east

http://www.wzkarten.de/pics/Rtavn784.png

Edited December 10, 2009 by neilsouth

[Snow Queen one]

Where has everybody gone? This run looks better to me the cold comes in quicker and is over more of the country now.

[Thundery wintry showers]

GFS seems to be continuing with the trend of producing a more immediate easterly into early next week (not of Siberian/Russian origin, but nonetheless from a fairly cold continent with 850hPa values around -10C). UKMO also moved towards this with yesterday's 12Z and today's 00Z. All very interesting, especially since until yesterday most model runs were going for a drizzly anticyclonic NE flow with only a few ensembles bringing the continental air in straightaway.

[snowmadchrisuk]

A very Snowy 12z with Snow possible from Sunday . 528 dam is also over England on Sunday . It also shows widespread showers over night Sunday into Monday.

Edited December 10, 2009 by snowmadchrisuk

[Megamoonflake]

Monday morning looking very interesting! NW Extra maps shows widespread snow showers!

[Neilsouth]

A very Snowy 12z with Snow possible from Sunday . 528 dam is also over England on Sunday . It also shows widespread showers over night Sunday into Monday.

Too warm for snow on sunday , however monday

http://www.wetterzentrale.de/pics/Rtavn962.png

-10 now clipping the SE by the middle of Monday

[Tom D]

Where has everybody gone? This run looks better to me the cold comes in quicker and is over more of the country now.

I think people are just waiting to see what happens, to save just getting their post deleted :lol: If you look at the bottom of the page, there's about 300 people lurking about

In any case, there's higher pressure over us this weekend, with colder upper air coming in sooner (Sunday morning). After that it all looks very similar, albeit shifted south a bit.

Things looking very solid up to +96, with -10 uppers just off the SE coast.

Edited December 10, 2009 by Tommyd1258

[mountain shadow]

This run really bringing the colder air in quicker. It's so different from the ECM run of only 12 hours ago.

[Optimus Prime]

Will be cold enough for snow showers across the east and south from Sunday in this 12z run. But the ground probably won't be cold enough for it to settle unless we get some cold nights.

[Neilsouth]

Heavy snow showers possible monday night , -10 across the south east

http://www.wzkarten.de/pics/Rtavn1022.png

[snowmadchrisuk]

Too warm for snow on sunday , however monday

http://www.wetterzentrale.de/pics/Rtavn962.png

-10 now clipping the SE by the middle of Monday

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.

[Nick F]

-10c t850s still creeping in across SE England Monday evening ... some snow likley off the N Sea. Unfortunately there is time for this to be downgraded but more of a cert than snowfall from the shortwave for down here.

[Rollo]

These charts seem to have more than a passing relationship to those of Dec,1962-the main difference is that back then Europe was much colder, I would have thought any snow for the North east would be confined to higher ground initially.

[Iceberg]

Very much a GFS rather than an ECM run, an upgrade for snow and cold on Monday (so much so that the BBC might start mentioning it signifcantly if the METO follows suite).

The LP bring the cold later in the run it still there at 96Z.

All good and we shouldn't really look any further (but we will just to see the pretty blues and pinks)

[Neilsouth]

Winds increasing across the south into tuesday , getting abit gusty im sure!

http://www.wzkarten.de/pics/Rtavn1081.png

Yep -10 aswell , heavy snow a strong possibility going by GFS for monday night

http://www.wzkarten.de/pics/Rtavn1082.png

Edited December 10, 2009 by neilsouth

[Thundery wintry showers]

Yes, I would certainly fancy my chances of waking up to a snow cover on Tuesday morning in Norwich if this output verified- as you say still time for it to downgrade, but the recent trend has been for this to appear almost from nowhere ("upgrade" would be too weak a term)- until yesterday it looked unlikely that we'd get any wintry weather of note before the 16th.

Re. the North East I wouldn't be surprised to see a widespread snow cover to low ground as long as you were in excess of 5-10 miles inland. We need those -10C 850's to become widespread over NE England for the north-east coast to stand much of a chance though (IMHO).

Shortwave looks favourably placed to bring the cold air across from the NE, staying well out to the east, so the scenario Kold Weather feared (low sticking over Scotland) looks unlikely to happen on this run.

Edited December 10, 2009 by Thundery wintry showers

[Snowstorm1]

These charts seem to have more than a passing relationship to those of Dec,1962-the main difference is that back then Europe was much colder, I would have thought any snow for the North east would be confined to higher ground initially.

Yes but by 6am monday morning snow at low levels across the ne e se would be very possible based on the charts

[Richie V]

-10c t850s still creeping in across SE England Monday evening ... some snow likley off the N Sea. Unfortunately there is time for this to be downgraded but more of a cert than snowfall from the shortwave for down here.

Also worthy of note, so far upto +105 hrs notice how much stronger the H500 heights are compared with the 06Z.

[Tom D]

Monday morning looking very interesting! NW Extra maps shows widespread snow showers!

I think it's got a bit carried away - minimum temps are around 3/4c so it'll be wet and slushy, if not sleet.

Definitely a better chance of snow showers in the south east overnight Monday, with surface temps around 0-2c and uppers of -10.