Model Output Discussion: 12Z (02/12/12) And On...

[Skeggy Winter Storm]

Good evening. Here is the evening review of the 12zs from GFS, UKMO and ECM for today Monday December 3rd 2012.

All models show a broad WNW flow over Britain tonight and tomorrow which turns towards the North on Wednesday. Following a ridge of High pressure on Wednesday night a new Low pressure area slips SE down the North sea by Friday with a further surge of cold North winds. Then a strong ridge of High pressure settles near Southern Britain over the weekend. The weather through the week will see showers, turning wintry by Wednesday. Rain moving SE on Thursday will be followed by further wintry showers on Friday before a cold and frosty weekend looks likely.

GFS then shows another small Low slip SE down the North Sea on Saturday and on into Europe on Sunday. This is the trigger for pressure to rise close to NW Britain which becomes absorbed by a large High over Northern Europe setting up a cold and wintry Easterly flow by the beginning of FI. Through FI itself this cold East flow dominates throughout, gradually becoming more unstable with sleet and snow showers near Eastern coasts becoming more prevalent later with more prolonged snow in the SW as milder air knocks on the door.

The GFS Ensembles show a cold spell is on the way with some snowfall possible at times. 850's stay below normal throughout with the operational on the lower side of the pack but not without support. The control run falls off a cliff towards the end of FI with some intense cold should that verify. There is though as usual at such range a lot of spread in the pack towards the end of FI.

The Jet Stream shows the flow tilting from its West to East flow to a more NW to SE flow taking it down to the Med before it turns East over Southern Europe. The Jet ridges High in the Atlantic in a week or so before turning South over the UK and maintaining its East flow over Southern Europe.

UKMO for midday on Sunday shows High pressure over Southern Britain and Northern France with a frosty and cold spell likely in the South but some bright daytime sunshine to compensate. In the North a milder SW flow is evident and though there will be more cloud it would likely stay dry. Good summary Gibby as always

ECM for the same time point shows High pressure too near SE Britain with a weak SW flow bringing slightly milder air for a while before Low pressure slips SE down over Denmark with rising pressure behind it over the Faroe Islands which becomes absorbed by High pressure over Northern Europe setting up a large cold block over Scandinavia with a raw and cold East wind developing over Southern Britain with snow showers running in to North Sea coastal counties later. The run closes with high pressure stretching from Northern Scotland to Northern Russia with a cold if mostly dry ENE flow bringing very cold conditions to the UK with frost by night and snow flurries in places.

In Summary the odds are increasing on an outbreak of cold for the UK. It's a rather messy picture to get there, though all three models show a similar route as High pressure builds strongly to the North and NE with a continental blast of cold air and the chance of some snow looking very possible from early next week onwards.

good Summary Gibby as always mate Edited December 3, 2012 by Skeggy blizzard

[Mucka]

I think its perfectly acceptable for people to get impatient and wonder whether an easterly will appear.

Regardless of how good the NH pattern is there are however no guarantees with weather, at the moment because of the expected placement of the PV and the ridge moving sw 'wards out of Russia then this does preclude a proper Greenland high but suggests something from the east.

Any high that forms to the nw is likely to topple eastwards, in the future as the PV moves back to Siberia the pattern of blocking is likely to change so that if you retain the same background signals high pressure at that stage is more likely to develop to the nw in Greenland.

It's understandable that people just want to get on with things and see at least the first hurdle overcome to an easterly, tonight the ECM delivers in its later output but shreds the nerves before hand, the GFS gets us to the easterly quicker and with less stress.

I think we'd all rather see the less stress option but you can only deal with the hand your dealt so if its to be the ECM version then it will come down to the shortwave being ejected se or s into the continent.

We've been here many times with easterlies and its really par for the course. Personally I think its unrealistic for everyone in this thread to view things from simply a standback, non -emotional this is just models attitude.

If people didn't have some emotional investment then it would be exceedingly dull, we're not the UKMO or NOAA, discussing what to release to the public.

So if the odd toys get thrown out of the pram, does it really do any harm! Certainly expect a cascade of them from me tomorrow if the outputs don't get a move on.

I've been on here for years and even though I try to be balanced and not come across as unhinged sometimes you just can't help yourself!

Who are you calling unhinged?

Good post Nick.

It is not just a matter of impatience though (although that is a part of it) it is seeing things for how they actually are and I think my analysis is fair.

Just to be clear though I am not predicting anything other than a cold easterly flow later next week, I am just saying the route there is a much more mundane and slow one than shown yesterday though GFS is a little quicker albeit still with little immediate appeal. I pointed out the reason for that so for me the output if anything is less appealing than yesterday overall rather than better as many seem to think since there will be very limited snow chances on the way to setting up the Easterly (ie not preluded by northerly and/or Northeasterly) for the reasons mentioned.

I guess some people are just more excited by high pressure over the UK than others - me, I like a little danger.

[Essan]

I think its perfectly acceptable for people to get impatient and wonder whether an easterly will appear.

It's perfectly acceptabe for people to get impatient and wonder whether a Bartlett high will appear ......

It's 3 days into a 90 day winter and we have a cold outlook, and easterlies are not the be all and end all of wintry weather in Britain. Anyone moaning at the moment is a moaning minnie who'd be moaning if he lived at the South Pole and it dodn't snow for 3 whole days ....

Edited December 3, 2012 by Essan

[nick sussex]

Still some room for manouevre with tonights ECM, the ensemble mean looks to have the pattern further west and a little less nerve shredding at 168hrs:

[Bristawl Si]

Who are you calling unhinged?

Good post Nick.

It is not just a matter of impatience though (although that is a part of it) it is seeing things for how they actually are and I think my analysis is fair.

Just to be clear though I am not predicting anything other than a cold easterly flow later next week, I am just saying the route there is a much more mundane and slow one than shown yesterday though GFS is a little quicker albeit still with little immediate appeal. I pointed out the reason for that so for me the output if anything is less appealing than yesterday overall rather than better as many seem to think since there will be very limited snow chances on the way to setting up the Easterly (ie not preluded by northerly and/or Northeasterly) for the reasons mentioned.

I guess some people are just more excited by high pressure over the UK than others - me, I like a little danger.

Not a great lover of a cold, dry spell either but IF it happens before a more snowier spell sets in then i'll take it.

Some of the best winters i've experienced have had a long feed of cold easterlies for days before pressure falls to the south/south west, heralding incoming fronts or channel lows - and then Boom!

[Mucka]

It's perfectly acceptabe for people to get impatient and wonder whether a Bartlett high will appear ......

It's 3 days into a 90 day winter and we have a cold outlook, and easterlies are not the be all and end all of wintry weather in Britain. Anyone moaning at the moment is a moaning minnie who'd be moaning if he lived at the South Pole and it dodn't snow for 3 whole days ....

Nobody has mentioned a Bartlett except you Essan, that's all I have to say about that.

Oh wait, thought I was gonna kick your ass but it appears I still have bubblegum

[kold weather]

Very impressve ECM ensembles at 240hrs, to get this sort of chart as a mean suggests some real eye candy in some of those runs:

http://www.wetterzentrale.de/pics/Reem2401.gif

[Froze were the Days]

Even if we do get there (to my untrained eye not a lot of difference between the GFS (+132) and ECM (+144) and as mentioned not a lot of margin for error to go all Pete Tong we still have that matter of the SW in the Norwegian Sea if we don't get enough energy pushing the Iceland LP south east and in turn no link up to the Scandy HP - just another hurdle to leap.

Cautious at the least at the moment, but good model watching all the same.

[Frosty.]

.

In Summary the odds are increasing on an outbreak of cold for the UK. It's a rather messy picture to get there, though all three models show a similar route as High pressure builds strongly to the North and NE with a continental blast of cold air and the chance of some snow looking very possible from early next week onwards.

My god Gibby it's not like you to RAMP, this must be your most wintry summary yet.

[chris55]

ECM mean days 9 and 10

[Cheshire Freeze]

Very impressve ECM ensembles at 240hrs, to get this sort of chart as a mean suggests some real eye candy in some of those runs:

http://www.wetterzen...cs/Reem2401.gif

Wow, based on that I'd expect some really frigid runs to show upon the ensemble plots.

Edited December 3, 2012 by CreweCold

[chionomaniac]

Just arrived home and have viewed the latest output today.

I don't know what to say other than I expected to see Scandi height rises at around days 7-10 and that is what the models are showing. No surprise that there are slightly different routes in getting there, but I knew that that would be the case. Certainly not worried about the UKMO 144 either as some are here. That is just 48 hours away from the easterly as well.

I expect now to see a number of very cold runs (-10ºC 850's) in the runs from around day 10 onwards as well. The ECM 240 is one primed chart!!!

[phil nw.]

Some posts are starting to stray off Model discussion.

I know the outlook is looking promising for continuing cold but can we refrain from general chat-there are plenty of other threads for general discussions.

Ok then back on topic please.

[The Northern Ramper]

Matthew Hugo â€@MattHugo81

ECM ENS clusters are grouped with 39 out of 51 members signalling a block to the N or NE beyond 216/240hrs. Other 12 have high over the UK.

[chris55]

Not a great lover of a cold, dry spell either but IF it happens before a more snowier spell sets in then i'll take it.

Some of the best winters i've experienced have had a long feed of cold easterlies for days before pressure falls to the south/south west, heralding incoming fronts or channel lows - and then Boom!

8 out of 10 times we get decent heavy snow in our region is by this route. Personally I really do enjoy the cold generally, but you can't get the white stuff without some cold air in place first so it's always important to get that bit done then look for the snow after..

[in the vale]

The NWP have all been bouncing around but the mean solutions have been headed towards a potentially very cold outlook for quite a while now. The truth is we already are in a cold spell for December - albeit not a very cold spell. My average temp so far (this is in the West) for Dec is 3.7c and the last double-digit temp day was 11 days ago. All the models are pointing towards several proper cold solutions - from different angles, which in my book is a brilliant position to be in on 3rd December. The posters who will not be satisfied until they have to scrape their frozen pets from the pavements really need to get some perspective on the situation. It will be cold. Very cold. And then it will get less cold. And cold again. And then potentially very cold again. This is a pattern that has all the hallmarks of being long lasting (not every day of the winter!) and certainly memorable. Please, look to the wider picture and don't waste your emotions on whether it will snow on thursday or sunday. Sometimes the surprises are magical and all the more enjoyable for it.

[Guest Kent-Weather]

Sorry to be a nuisance but can anyone give me the link, where it shows snow as a snowflake (3 if heavy) and rain as a green circle? On precipitation charts.

http://www.weatheronline.co.uk/cgi-bin/expertcharts?LANG=en&MENU=0000000000&CONT=ukuk&MODELL=gfs&MODELLTYP=1&BASE=-&VAR=rart&HH=3&ARCHIV=0&ZOOM=0&PERIOD=&WMO= This one?

[snowking]

Pretty spectacular when 51 ensembles averaged produce that at 240

This from Matt over on Twitter:

ECM ENS clusters are grouped with 39 out of 51 members signalling a block to the N or NE beyond 216/240hrs. Other 12 have high over the UK.

Bearing in mind ensemble forecasting is used as a tool for probability forecasting, what we are saying is thats a roughly 80% - 20% split in favour of easterly vs HP over UK (give or take 3% - if we want to be more exact its nearer 77% - 23%)

Would be interesting to hear what the MOGREPS ensemble suite offers in terms of support for the ECM....

SK

Edited December 3, 2012 by snowking

[Mucka]

Matthew Hugo â€@MattHugo81

ECM ENS clusters are grouped with 39 out of 51 members signalling a block to the N or NE beyond 216/240hrs. Other 12 have high over the UK.

Seems about right. The ensemble mean certainly reflects that.

http://www.wetterzentrale.de/pics/Reem2402.gif

[SMU]

Still some room for manouevre with tonights ECM, the ensemble mean looks to have the pattern further west and a little less nerve shredding at 168hrs:

THe important thing about the Ensemble mean tonight isnt so much around the trough sinking south, but the absence of any shortwave spoilers.

Remember people this is really important- The pathway to a cold spell from the North or East is complicated by only one thing- how many transitions you have to through & at what point + T0 they begin.

Some cold high & easterlies transition at 204 & deliver at 240-300 which is what I would class as FI-

You have to treat every evolution on its own merits-

It this particular case there is ONE transition which is brough about by the trigger low at 144- now thats NOT FI- so there is I would say a near 90% chance of that low developing, its just the curvature of the jet to get it into holland as opposed say Germany thats the issue.

Its one of the easier progressions I have seen, but still not straight forward- there is no straight forward evolution to a big easterly.

ECM 10 day ENS

http://www.knmi.nl/e...M_06260_NWT.png

suggests that the op & control are slightly deep & to far east with the trigger low- thats my abstract from that-

other than that awsome.

S

HERES ONE FOR THE SCOTS- Could they hold onto that snow cover for ALL of december or even ALL of winter!!!

Edited December 3, 2012 by Steve Murr

[cold snap]

After reading gibbys assessment you would wonder what all the fuss about

It's going to turn colder with a chance of snow

.

This is a patience game but that is running thin for some of us ,understandable if you ask me

Edited December 3, 2012 by cold snap

[The Northern Ramper]

Pretty spectacular when 51 ensembles averaged produce that at 240

This from Matt over on Twitter:

Bearing in mind ensemble forecasting is used as a tool for probability forecasting, what we are saying is thats a roughly 80% - 20% split in favour of cold (give or take 3% - if we want to be more exact its nearer 77% - 23%)

Would be interesting to hear what the MOGREPS ensemble suite offers in terms of support for the ECM....

SK

I would say 100% cold but 80/20 precip mix or dry.

[Mucka]

I come in from a 12 hr shift and try to catch up on model output discussion and you post a IMBY snow grunt come one

And they didn't have your tea on the table!

That is a very striking ECM ensemble mean chart even at 216.

Edited December 3, 2012 by Mucka

[Long haul to mild]

JMA is certainly not interested in an easterly tonight!

http://www.meteociel.fr/modeles/jma.php?ech=192&mode=1

I suppose this is just one of the solutions on offer in what will undoubtedly be a very cold period coming up.

[snowking]

I would say 100% cold but 80/20 precip mix or dry.

Sorry yes you're completely right, 80/20 split in terms of easterly or HP over us

Will ammend original post

Incidentally even if we get the HP over us, hopefully tonights ECMWF has shown you what happens under large HP's in terms of the 850 pool:

http://www.wetterzentrale.de/pics/Recm1922.gif

Moderate 850 pool

48 hrs later:

http://www.wetterzentrale.de/pics/Recm2402.gif

SK