Model Output - General Discussion

[Glacier Point]

Can i assume from your last sentence GP, that a possible 'battleground' LP approaching from the south west is a distinct possiblity on Xmas Day?

... the assumptions would be a southerly tracking jet with longwave trough located over the UK and cold uppers more than capable of supporting widespread snow, at least on the leading edge.

The timing of any event is only going to be marked at t72 down but the conditions will be ripe leading up to and including the day IMO.

[guitarnutter]

In a way I hope this downgrades a little as those charts are truly terrifying in a way with what is coming to the North on xmas day on top of the 3-4ft of snow they will be under, by boxing day half of Britain could have 7 or 8ft of lying snow and 40ft drifts and that would not exactly be sledging weather with snow up to the necks of everyone who is not a pro basketball player, that is huge loss of life weather

Save it for the ramping thread!

If only Europe was cold

[SMU]

http://91.121.94.83/modeles/gens/run/gens-21-0-120.png?18

Ensemble mean FINALLY reaches -10C for the SE at 120----

Also the Ensemble mean for 144 is -10C moving through Scotland-

http://91.121.94.83/modeles/gens/run/gens-21-0-150.png?18

A great night..... we are now on the final run in to something that could be the sort of charts that I am posting up in 20 years as an archive to praise!!!!

S

[on the coast]

FAX charts:

T+96: http://www.meteociel.fr/ukmo/fax/fax96s.gif

T+120: http://www.meteociel.fr/ukmo/fax/fax120s.gif

Worth the wait I'd say!

Quite different from the 18z?

[johnholmes]

lucky you-I'll be watching from above or below, I've not yet been told where by the grim reaper!

[kold weather]

The 18z GFS shows what could happen if the low takes a different path, be in no doubt that if it heads northwards towards Newfoundland rather then straight due west like the 12z ECM then odds are pretty good that the cold sustains at least at lower levels till xmas.

Early days but hopefully this will be a trend we are seeing on the models, who knows though!

Anyway I'm getting increasingly confident on there being snow in the SE its just somewhat uncertain through what method...beyond that the northerly is also becoming increasingly likely it seems after a small wobble last night.

[phil nw.]

FAX charts:

T+96: http://www.meteociel.../fax/fax96s.gif

T+120: http://www.meteociel...fax/fax120s.gif

Worth the wait I'd say!

Yes indeed.A good flow there.Wouldn`t suprise me if the later fax`s show more minor troughs nearer the time Paul.

Not much time to catch our breath either before it`s big brother arrives from the North.

Exciting times.

[guitarnutter]

We are almost forgetting the 1065mb Greeny high at T+90!

http://91.121.94.83/modeles/gfsp/run/gfs-0-90.png?18

[Cloud 10]

Quite different from the 18z?

Those updated fax charts are carbon copies of the 12z ukmo.

This is a very good thing.

[johnholmes]

In a way I hope this downgrades a little as those charts are truly terrifying in a way with what is coming to the North on xmas day on top of the 3-4ft of snow they will be under, by boxing day half of Britain could have 7 or 8ft of lying snow and 40ft drifts and that would not exactly be sledging weather with snow up to the necks of everyone who is not a pro basketball player, that is huge loss of life weather

John

a word if I may

IF you changed the totals to cm's people might believe you in feet and inches then you sound just a little OTT-I notice others seem to think along similar lines to my comment

[03jtrickey]

Right then , although im pleased to see the charts, the cold is continuasly putt bk , at least the severity of it is . And its fustrating to say the least , theeasterly forecast was meant to be snowy, but now looks slack, i wish i was wrong but why should this be any different ?? Yes the potential is there but the outputs change and the chances keep on been delayed . Im a massive snow lover and hopw im wrong , i stand to be corrected and i ones have evidence to tell me otherwise pls do as i wanto be wrong , but just sayin it as i see it , thoughts welcome , thanks

This is stunning output at the moment - it doesn't get better than this! Firstly we have a potential snow event on Tuesday evening, then the easterly for Thurs/Fri is looking snowy... then a snowy weekend with a Northerly. I can't see how the cold is being put back. -6 uppers arrive in the east by Weds on the 18Z - same on the 12Z. Given the ppt today in the east with much warmer upper air temps, on Thurs/Fri with uppers of -8 to -10 whether the easterly is slack or not there will be convection and showers in the east.

[Mikel Nimbus]

The main trend of most of the charts over recent days has been to split the joined Greenland High and the Siberian high progressively more west. Last week this split was expected to occur somewhere over Scandinavia/Eastern Europe, now it is happening directly over us, opening the floodgates to low pressure bringing us all a freezing northerly by next weekend.

I can't see a more ideal breakdown of the Easterly than this to be honest. It's looking very promising guys.

[andymusic]

http://91.121.94.83/...21-0-120.png?18

Ensemble mean FINALLY reaches -10C for the SE at 120----

Also the Ensemble mean for 144 is -10C moving through Scotland-

http://91.121.94.83/...21-0-150.png?18

A great night..... we are now on the final run in to something that could be the sort of charts that I am posting up in 20 years as an archive to praise!!!!

S

You might not need to save them - Joe - Laminate Floori was on about how cold this "winter" was going to be over six months ago along with the fact that over the next 20 years plus this could become the norm due to the current solar set up - and whether the governments of the world really think they can "control" the earth's temperature

Edited December 13, 2009 by andymusic

[Tim Bland]

John

a word if I may

IF you changed the totals to cm's people might believe you in feet and inches then you sound just a little OTT-I notice others seem to think along similar lines to my comment

Well said John. People on vairous threads talking about panik buying shovels and snow chains ready for the 12ft of snow. This is NOT shown on any model and NOT going to happen!! It is irresponsible of the posters as some less eduacated might belive it and start spreading it around work / friends / family etc and causing panick. I think we need to take a few days at a time. At the moment I am only lookind at the chance of snow on Tues night / Weds after then is subject to change. The only thing I would panic buy is a sledge if you live on high ground in the North East!

[John Snow]

Well said John. People on vairous threads talking about panik buying shovels and snow chains ready for the 12ft of snow. This is NOT shown on any model and NOT going to happen!! It is irresponsible of the posters as some less eduacated might belive it and start spreading it around work / friends / family etc and causing panick. I think we need to take a few days at a time. At the moment I am only lookind at the chance of snow on Tues night / Weds after then is subject to change. The only thing I would panic buy is a sledge if you live on high ground in the North East!

Even if I got the totals a bit wrong I do think some areas are going to get snow totals in feet and not inches although admittedly this is more likely in Tyne and Wear and Yorkshire than the South but we saw last Feb that the country is ill prepared for massive snowfall totals and I doubt lessons have been learned and if what I say happens and some areas get feet then its going to cripple that region so yes if there are people in Yorkshire and Tyne and Wear here it is a good idea to be "panic buying" as whole areas would be cut off if the 18z verified, maybe 7-8ft was a bit exaggerated in hindsight but I think at least 2ft is realistic for the areas I listed above

You are being complacent and I over exaggerated, I think the end result should be between the 2

[kold weather]

Paralell run is quite frankly stunning as well, a LP in a cold airmass swings WSW over the UK, cold air filters back in and then the same low attacks overnight on the 25/25th probably giving a real dupming as well as a white xmas.

Most ensembles are still very hasty to break the pattern but the ops are very interesting, there certainly have been hints on recent runs on this extending on the ops run of the GFS, as did the 0z ECM...big uncertainties...

For once we can watch FI safe in the knowledge that we already have cold!

[john mac]

Well, i have been sitting quietly watch this situation unfold over the last few days, many ups and downs as usual good posts bad posts and as usual great work by the mods, steve, nick, kold and john etc( apologies if i have forgotten anyone), its been really nail biting stuff andthis is just the beginning thanks everyone and long may it continue

[Thundery wintry showers]

I don't see the cold air being put back? The easterly for Monday/Tuesday was always an outside bet, which the GFS latched onto for a couple of runs and the UKMO supported for one run, while the ECM never had anything of it.

The main potential was always Thursday onwards, and while the current outputs perhaps don't show the fantasy scenarios that the GFS parallel had, the easterly does look like sustaining for long enough to bring a snow event to some eastern, especially south-eastern, districts. Most importantly there has been no downgrade of the intensity suggested by a couple of ECMWF runs a couple of days ago which had the jet running to the north of the block and sinking it south.

The subsequent northerly will not be as intense as the GFS 18Z shows- I can say that for certain, the progged temperatures simply do not match up with the airmass profiles. But it has the potential to snow-cover virtually the entire country and the charts do have a "late January 1979" ring to them.

[Frosty.]

The subsequent northerly will not be as intense as the GFS 18Z shows- I can say that for certain, the progged temperatures simply do not match up with the airmass profiles. But it has the potential to snow-cover virtually the entire country and the charts do have a "late January 1979" ring to them.

WOW that is some Northerly on 18z but as you rightly say, there is no chance of that happening, if it did we would be looking at a dec 1995 event for the northern isles and north east scotland with huge snowdrifts piling up over 20 feet high, no way.

The 18z at least gives us a flavour of what to expect though and the northerly probably won't be shunted too far east as is the norm which will make a nice change although I still expect it to reduce in intensity over the coming days.

Edited December 13, 2009 by Frosty039

[swilliam]

Looking at the FI possible evolutions (I know JH says we should only enjoy the cold spell but model watching is also about looking at possible scenarios coming up) it is interesting to look at the Reyjavic pressure ensembles.

Out to 23/12 we can see the drop corresponding to the dropping on of the Northerly low pressure system. Beyond that there is huge diversity with by the pressure varying from 1038 to 958 mb. The op run is near the top of this range. Depending on which evolution occurs gives vastly different outcomes. First for Reyjavic the HP means the op is near the top of the temperature range.

Conversly for us it is at the bottom of the range.

Therefore depending on whther you live in Iceland or the UK would determine whih of these solutions you might prefer.

One small gripe - we were discussing this possible easterly in FI about 5 days ago and were told by SP that it was in FI and also implausible. We were also told by others that it would never verify. Well it looks like it is plausible and may well verify - not exactly as was portrayed then but correct in the overall scheme. So please if we do discuss FI do not keep telling us it is in FI (we know that) or that it won't verify - we also know that most of the time that is also true - but it does show what is possible and that is what we like to discuss.

Stewart

[TEITS]

Only just seen the fax charts, still haven't seen the GFS Parallel as i've been too busy shooting americans on Modern Warfare 2 which is my other favourite hobby.

Im not at all surprised to see the Fax charts supporting the UKMO. Don't forget the duty forecaster wouldn't of just looked at the UKMO but all of the other data and then used his forecasting skill to decide which is most plausible. This is excellent news and I shall be intrigued to see what the 0Z UKMO suggests.

I see the mean has now dropped to -10C for Cambs.

http://charts.netweather.tv/ensimages/ens.20091213/18/t850Cambridgeshire.png

[Typhoon John]

If I could pick a run until Christmas I'd bank the GFS 18z now. The run is superb and a especially stunning for North East England where I obviously have more of an interest.

Firstly there's enough cold and disruption to cause snow showers from lunchtime Wednesday through until Friday.

Even though the GFS doesn't show it I'd expect some precipitation early Friday morning from this.

And then the Northerly dropping out of Scandinavia is a delight.

But everyone should see something from this and there'll probably be more precipitation about than shown by the models at the moment. There'll definitely be some polar lows in that Northerly flow but where they'll hit is a bit of a lottery. But really, what more could anyone want? And we're not even halfway through December!

[kold weather]

WOW that is some Northerly on 18z but as you rightly say, there is no chance of that happening, if it did we would be looking at a dec 1995 event for the northern isles and north east scotland with huge snowdrifts piling up over 20 feet high, no way.

The 18z at least gives us a flavour of what to expect though and the northerly probably won't be shunted too far east as is the norm which will make a nice change although I still expect it to reduce in intensity over the coming days.

Thats the thing Frosty, the northerly ends up becoming a cyclonic circulation over the UK with some very low thicknesses for such a system on the GFS. You'd be looking at probably a fair few disturbances in the flow and in all likelyhood probably quite a lot of snow for places that wouldn't normally have much of a shot in a standard toppler northerly.

Generally very mixed FI though generally fairly cyclonic in nature but exactly what type is something that isn't well agreed upon, even if we do get a breakdown wouldn't shock me to see a reload towards the end of the month, there are some members that strongly hint at it.

[The Enforcer]

Some decent charts here with a midweek easterly being followed by a weekend northerly, which now looks to be a fairly reliable pattern. Comparing Saturday's and yesterday's GEFS 18z ensembles, there seems to be greater agreement with the overall pattern for upper temperatures over the next 5 days, with the first signs of any mild air being pushed back from 19th to 2nd. I've attached these below as the full editor doesn't seem to want to work on this post.

As ever, the devil is in the detail and as for the last 3 winters/springs I'd be looking for some frontal activity in there to guarantee that this cold spell delivers what it is currently promising.

One question, how does this all this square with the NW winter forecast provided to commercial organisations, but made available to us last month, which basically said mild December, cold spells in January and uncertain February?

Edited December 14, 2009 by The Enforcer

[The Enforcer]

Sat 18z:

Sun 18z:

Edited December 14, 2009 by The Enforcer