winter model discussion Winter Model Discussion 06Z 17/02/13 onwards.

[cooling climate]

Attack from the SW has been pretty much none existant these past few days.

I will add its going to be difficult to maintain any snow cover due to the time of year regardless of temps. For this to happen locations are going to need plenty of cloud cover and little sunshine.

Personally im not bothered about days of lying snow or how prolonged this cold spell could be. I would be content with a few days of snow showers and anything else is a bonus.

I remember that February 86 was one of the driest sunniest Feb's on record and yet

we along with many parts of the country had laying snow from fairly early Feb right

through to the end of the month. A look through the archives shows that at times

850 temps were not much to wright home about either although low dew points and

bitterly cold night time temps may have helped considerably.

[CWT2012]

Good upgrades from the important models, good potential for a Thames streamer as the winds move ENE from E plus good chance of heavy snowfall at 144 if the northwards progression continues

[bluearmy]

The ops are certainly keen to drift the higher heights towards mid atlantic. Ecm fi certainly paints a more interesting profile possibly allowing the block to get far enough west to allow the frigid trough to back west. Long shot but each run seems to be lowering the chances of the favoured gfs low res route back to souwesters. I'd just like to see the ecm ens less bullish to raise temps so far week 2. Was an interesting fi spread on uppers on the 00z run. No point in analysing it in detail until it repeats.

[nick sussex]

Overall this evening a better trend developing but I'd like to see the cold pool come within T72hrs.

Its been interesting how its been a case of one piece of the puzzle in then another one won't fit properly, so now that the cold pool to the east looks like being condusive but where exactly does the coldest air get directed.

Personally I'd like to see those -13s make a direct hit on the UK just to see how much fun and games that could bring! Theres still a chance that could happen but also theres not a big margin for error at least initially.

We've seen from this mornings output just how crucial these small changes can make to the UK so until T72hrs I'd be a bit wary of being confident.

Looking at the overall ECM run its very good for some but doesn't deliver for areas further north which are furthest from the coldest uppers and instability.

So I think our next mission is to see whether we can squeeze a decent retrogression of the high with a northerly airflow, I think the ECM 240hrs looks like trying but we're not really seeing a clear signal from either the GEFS or the ECM ensembles over recent days.

Generally you would expect to see especially the GEFS to be picking up on this,so for the timebeing I don't think people should assume that its going to be a natural progression given the ECM operational run.

We'll see whether the next few runs build on that trend....

[snowking]

http://www.meteociel...H1-240.GIF?17-0

At 240 my initial thought was a sinker- but if we look- greenland has cleared of the JET & the atlantic has great vertical advection.

Also a trigger low neatly lined up east of greenland to recurve over us.

The models have granted me a stay of execution tonight-

Looking good this week, I would say 3 ice days on the bounce for me & very very close elsewhere......

I will be interested in both Ians thoughts on the 12's more particular the shower train potential....

S

Same here steve but good spot!

Here's the jet stream at 240 (Greenland top right):

And if we take a look at it coming out of the USA:

All the energy piling out of the USA well to our south, and it leaves things pretty well placed into the period beyond.

In the shorter term, ECMWF projection of snowfall > 1 inch:

Still nothing substantial at the present time, but a decent trend.

Precipitation projection at 144:

And it looks like a more organised area of sleet/snow at 168 for southern areas:

So, certainly a step in the right direction tonight from the ECMWF, both in the shorter and longer term.

To keep people grounded somewhat though, this will continue to shift around somewhat for some days yet (I would be surprised if we had a clear projection of the situation any earlier than Wednesday)

SK

[Weather-history]

Hmmm New Years Day 1997

http://www.meteociel.fr/modeles/archives/archives.php?day=1&month=1&year=1997&hour=0&map=0&mode=0

[stodge]

Evening all

As others have stated, some very solid charts this evening for fans of cold and please allow me a modicum of IMBY-ness, promising for snow in lowland East London though I'm under no illision that any snowfall will be fairly transient in nature.

http://www.wetterzentrale.de/pics/Rtavn12017.png

Cold certainly (compared to 8c today) but not an ice day and I'm hoping against hope we will import drier and clearer air to provide some low night-time minima (the short-lived mid-December spell remains the coldest in terms of night values for the winter).

http://www.wetterzentrale.de/pics/Rukm1201.gif

Again, not warm though I note the developments to the NW which seem to mitigate against an early retrogression and might explain the evolution to T+144.

http://www.wetterzentrale.de/pics/Recm1201.gif

Oddly enough, I'm less enamoured of this than some. There seems plenty of energy moving NW of the block and those who think said block could well sink might look at a chart like this as justification for their argument.

http://www.wetterzentrale.de/pics/Rgem1201.gif

A fantastic chart in almost every respect but others have poured cold (or should that be warm) water on the model and disregard the chart.

http://www.wetterzentrale.de/pics/Rngp1201.gif

But topped by this beauty which shows what's possible if the HP moves north and the energy moves SE.

I'm going to reserve judgement until I've seen tomorrow's output but I don't wholly disregard either the sinking block scenario or the snowy scenarios of GEM and NOGAPS.

[cooling climate]

Great ECM t240 chart with bags and bags of potential. I was beginning to wonder

where the SSW high latitude blocking to see out February and on into March had

gone and with it perhaps the coldest weather of the winter.

[Ian Brown]

Yep, very true Steve. High temporarily sits over UK but looking at the bigger picture it's loaded with potential. Look to NW would be a good hint if the run went out further because I'm sure that's where the high would be headed.

I'm absolutely convinced it isn't - the jet profile is all wrong and I would think the T240 ECM and GFS ensemble mean are fair reflections of where the High will be before a slow and gradual sink, but all a long way off.

Good to see the Southward trend ended tonight therefore bringing more of Southern england into play for light snow, I maintain nothing more will come of the set-up once that link up of heights from the Azores to 'our' High has occurred in that T120-144 timeframe, which the ECM displays, supporting the UKMO and GFS at the same time.

Edited February 17, 2013 by Ian Brown

[london-snow]

good call there.you should join the meto!

Well what can i say..

Better than posting one liners & at least I am tying to be positive unlike some of the posts that I have seen today.

[Cheshire Freeze]

I'm absolutely convinced it isn't - the jet profile is all wrong and I would think the T240 ECM and GFS ensemble mean are fair reflections of where the High will be before a slow and gradual sink, but all a long way off.

Going to have to diasgree Ian. Ensembles pretty useless IMO for reasons I suggested the other day. ECM pulls energy under the block at 192 which the GFS fails to do (sound familiar?) If the GFS op fails to spot this at that juncture then the ensembles have absolutely no chance......which was seen in the run up to this impending cold spell. The 240 ECM chart is loaded with potential (as Steve has rightly pointed out), though as ever at that timeframe it's pure conjecture.

You'd do well to read a couple of posts up to see why the 240 chart isn't a sinker....Snowking has put the jetstream chart up.

P.S when Steve said he'd like to hear from Ian in his post on the last page, I'm pretty sure you're the Ian he didn't have in mind

Edited February 17, 2013 by CreweCold

[Stuie]

Same here steve but good spot!

Here's the jet stream at 240 (Greenland top right):

And if we take a look at it coming out of the USA:

All the energy piling out of the USA well to our south, and it leaves things pretty well placed into the period beyond.

In the shorter term, ECMWF projection of snowfall > 1 inch:

Still nothing substantial at the present time, but a decent trend.

Precipitation projection at 144:

And it looks like a more organised area of sleet/snow at 168 for southern areas:

So, certainly a step in the right direction tonight from the ECMWF, both in the shorter and longer term.

To keep people grounded somewhat though, this will continue to shift around somewhat for some days yet (I would be surprised if we had a clear projection of the situation any earlier than Wednesday)

SK

So glad you are my "neighbour" SK, Your posts are very detailed. If we believe the GFS precipitation forecast then "peppering" on our little bit on the map could become interesting.

[swfc]

Well what can i say..

Better than posting one liners & at least I am tying to be positive unlike some of the posts that I have seen today.

Iwas actually congratulating there on your post!Sorry about the one liners but im quite busy during the day ete

[DAVID SNOW]

Hmmm New Years Day 1997

http://www.meteociel...=0&map=0&mode=0

Good spot there,and if you scroll down to chart 7 you have a COBRA run

[I remember Atlantic 252]

Hmmm New Years Day 1997

http://www.meteociel...=0&map=0&mode=0

My white new year, not had one since then

[johnholmes]

the link to the promised update using 500mb charts and a brief look at prospects for later this week

[Methuselah]

Now that that's over, we can hope for some some more information from Fergie, as to how the Met's ideas are developing...

[london-snow]

Iwas actually congratulating there on your post!Sorry about the one liners but im quite busy during the day ete

Not directed towards you & thank you.

As i was pointing out earlier to you i really do hope that the high trends that bit north to bring the majority of england into play.

Now that we seemed to have stopped the rot that rot being the high trending south we now have things slowly trending that bit north going by the 12z and some of the 06z runs.

So if this continues to trend north bit by bit then come the start things may look a whole lot different to what is currently being shown.

Best of luck to you & i hope we both are enjoying a snowy spell come the end of next week.

L~S

[Gibby]

Good evening. Here's tonights report from the 12zs of GFS, UKMO and ECM for tonight Sunday February 17th 2013.

All models show a settled and dry spell of weather to come through the working week. With High pressure developing up to the NE there will be dry weather for all tonight and tomorrow with a moderate SE breeze keeping things less foggy tonight in the Central Southern districts with any fog more likely towards the NE. Tomorrow will be another bright day with sunny spells though the far East and SE will be more cloudy. By Tuesday a ridge will axis South across the UK with quiet weather continuing with some bright spells and less wind than tomorrow and temperatures close to normal. Through the middle of the week a weak front moves West over the UK with cloudy weather with perhaps a spot of rain or drizzle in the developing light Easterly breeze. Towards the end of the week the South sees the East flow really pick up to a strong breeze while the North will see quieter and probably brighter conditions in the NW where temperatures could fair rather better than elsewhere. The temperatures show a continuation of the cooling off late in the week with some snow grains or light snow flurries possible in the far South and SE.

GFS then shows the NE flow weaken over the weekend with High pressure sliding slowly South over the UK with cold and potentially frosty weather for all with dry weather too mintained for all areas. Through the following week fine weather persists in a fairly flabby area of High pressure with continued frost and fog patches with all areas unlikely to see anything in the way of precipitation. Daytimes too will be rather cold especially where cloud persists. By the end of the run SW winds do take hold as High pressure finally moves off to the SE with rain and wind returning off the Atlantic with some snow possible over the hills of the North.

The GFS Ensembles show a sharp drop in the uppers over the UK before a steady climb to levels above average by the second half of the run well supported by the group. The operational stayed on the cold side of the pack for longer following the cold snap with rainfall only a feature at the end of the run.

The Jet Stream shows the flow currently setting up as a dual flow one well North of the UK and one well South which persists for some time. Later a Northward push from the Southern flow West of the UK sets up a stronger Northern arm in a week or so.

UKMO for midday on Saturday shows a High pressure belt from Scandinavia to the Azores with a High centre over the Hebrides. A cold NE flow is maintained over England and Wales and there would probably be a few wintry flurries in the SE. Frost would be widespread for the north where skies stay clearest but the South may be affected by more cloud cover restricting night time deep cold but the same cloud will suppress daytime temperatures too.

ECM too shows High pressure close to the North of Scotland at the same time point and maintains it there through to the end of the run. A very cold and dry spell is maintained over the UK with just the occasional snow shower or flurry possible at times in the South and SE.

In Summary tonight High pressure is to be dominant for the foreseeable future. With it's position close to the North of Scotland a NE or East flow is maintained over Southern Britain though there is little sign of anything particularly wintry in the offing even here. Instead it looks like we will be chasing cloud cover which will make all the difference to the ambience of the days over the next few weeks. If skies clear then some quite low temperatures may be observed but in prolonged daytime sunshine the far West and NW of Britain despite sharp night frosts would see temperatures not far from normal. The breakdown hinted at from GFS is way too far out to be taken serious on at the moment but it's ensemble members are particularly bullish about a steady rise to rather mild conditions later in week 2.

[Froze were the Days]

Better charts tonight...thank God! still a lot of 'ebbing and waning' with such fine margins on the synoptics at present. Let's all wash our cars mid-week and we're bound to get some precipitation

[BLAST FROM THE PAST]

Now that that's over, we can hope for some some more information from Fergie, as to how the Met's ideas are developing...

Well they had 7c and then 8c for London Tues / Wed this morning....Getting milder by looks of it

BFTP

Edited February 17, 2013 by BLAST FROM THE PAST

[R.P. McMurphy]

But the evolution to 216 seems a bit odd to me?

Looks good to me, reminds me of December 27th 2009 with the LP sinking deep into the Atlantic, allowing heights to building massively over Greenland, I'm not too fussed over the UK High.

[AWD]

Looks like a sustained period of settled and drier than average conditions likely, with high pressure close by to the UK, with its position determining the air source and surface temperatures we are likely to receive;

The depths of FI show both the Op and control quicker than the ens suite to lose the high pressure and bring back PPN.

[fergieweather]

Well they had 7c and then 8c for London Tues / Wed this morning....Getting milder by looks of it

BFTP

Cold feed of the very subsided airmass doesn't usher-in fully from E until passage of the weakenIng front after mid-week.

[snowblizzard]

http://www.meteociel...H1-240.GIF?17-0

At 240 my initial thought was a sinker- but if we look- greenland has cleared of the JET & the atlantic has great vertical advection.

Also a trigger low neatly lined up east of greenland to recurve over us.

The models have granted me a stay of execution tonight-

Looking good this week, I would say 3 ice days on the bounce for me & very very close elsewhere......

I will be interested in both Ians thoughts on the 12's more particular the shower train potential....

S

Are you sure Steve?

The BBC Countryfile forecast was very underwhelming even for the SE

Maximum of 4c in London on Friday with hardly any mention of the 'white stuff'!