Winter Model Discussion - The Hunt For Cold - 12th Dec

[TEITS]

Have to be honest if someone asked me for a forecast on xmas day I would say "It will be relatively mild and unsettled" or "very cold with snowfall possible". The model output this morning is the kind that can easliy swing both ways and if you are suffering from model trauma due to the recent disappointment then take a break.

The differences occur fairly early on. The ECM between +96/+120 is much keener on sending that LP SE at +96 and at +120 the block to our E is further W and the LP in the Atlantic is also further W.

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

After this is when it gets even more confusing because its all about whether the Atlantic LP goes SE into Europe. If it does then the charts at +240 on the ECM are perfectly plausible because our block to the NE isn't going anywhere and that energy going SE allows the block to ridge W.

http://www.wetterzentrale.de/pics/Recm2401.gif

I haven't looked at each GEFS member but upper temp wise very little support for the ECM and yet the 0Z follows the 12Z in sending the LP SE bringing an E,ly to the UK. Personally the ensembles are pretty useless in my opinion due to the differences in the operationals at a relatively early timeframe.

I will finally add though that this could be an opportunity of making a few quid at the bookies especially if they raise the odds of a white xmas due to our impending mild weather. If the ECM is right and the other models follow suit it will be a few days before the bookies get wind of it!!!

[Tom Montalbano]

If you look at the GFS and ECM at T192-240, then the differences are relatively minor and it wouldn't take much for either to go the other way in terms of where the boundaries are between the Atlantic and the Continental air. It's only later that the GFS brings a dominant PV into play.

Any thoughts this morning GP ? Other than an each way bet to nothing on Melodic Rendezvous in the last at Cheltenham ?!

Hi Ian,

Yes, small differences to these pressure patterns can make a huge difference to our small island, 500/1000 miles, like popping to the corner shop for a pint of milk.

Some members were worried where Stewart was........obviously studying form for Cheltenham Friday/Saturday.

Whats this with tipping horses up, you know we Bookmakers get very touchy about that!

But surely you've got to have a little on The Big Freeze (12.45) and double that up with Midnight (snow) Chase (1.55).

If you guys are going, have a profitable couple of days but dont you go backing to many winners with us on the Rails!

Regards,

Tom.

[Timmytour]

The movement of the easterly extent of Atlantic domination back westwards is slow, erratic and inconsistent, but I have a feeling today's runs will be more resolute in modelling it

[nick sussex]

The Xmas Miracle hangs by a thread this morning after the overnight runs decide not to develop a deepish shortwave on the southern flank of the trough.

So many times shortwaves pop up to derail cold synoptics here we want one to develop off the eastern USA, this shortwave took some energy se and at the same time helped pull the trough nw as it engaged it.

Theres a certain irony about this or just another sick modelling joke!

There are still differences between the outputs especially with an earlier shortwave cutting into Holland, the PV does show signs of splitting so that is a positive but after last nights excitement its back to reality today.

Whilst the jet continues to track quite far south we remain hopeful but we certainly need a little help upstream.

If you look to the sw of the trough near the UK, you can see the shortwave trying to develop but this doesn't manage to and just gets absorbed by the main trough, in yesterdays ECM this shortwave develops running se taking some energy se and away from the main trough, at the same time it helps to pivot the northern part of the trough.

Still waiting to see the ECM ensembles to see what they make of things.

Looking upstream there are differences this morning with the speed of shortwaves crossing the USA also and its this and the lack of that shortwave developing which culminate in the changes, as I said a yesterday its a complex set up with timing and shortwave interactions being critical.

Edited December 14, 2012 by nick sussex

[Nick F]

An olive branch again towards a colder outlook from ECM with its southerly tracking jet later in the medium range, but IMO history is against this kind of evolution, particularly with no major blocking to the north of the UK.

00z GFS operational has plenty of support too to continue the westerlies, so I'm not going to be drawn towards the ECM's southerly tracker yet ...

[bradymk]

Any update on the ECM 32 day today?

[beng]

Any update on the ECM 32 day today?

There's a twitter comment from Joe laminate floori that it's showing negative NAO for next 30 days (believe it when I see it!) - hopefully Matt will be along at some point with an update.

Edited December 14, 2012 by beng

[snow drift]

An olive branch again towards a colder outlook from ECM with its southerly tracking jet later in the medium range, but IMO history is against this kind of evolution, particularly with no major blocking to the north of the UK.

00z GFS operational has plenty of support too to continue the westerlies, so I'm not going to be drawn towards the ECM's southerly tracker yet ...

Certanily the more logical view but we are cold weather fans and where is the logic in that?! At least it gives us some interest. Has anyone got an example chart where it did track southerly?

[Uncle_Barty]

A look at the model output over the past few days tells me that things are a little messy generally. I'm not looking beyond 5 days, as even looking for trends beyond then is hard.

On the face of it, looks average/perhaps mild at times esp in south, and unsettled for the foreseeable looks to be the form horse, and those talking up any return to cold are little more than hope/wishcasting.

But... I think we are in the kind of situation where we could be faced with a change to much colder weather again at relatively short notice from nowhere, perhaps 144/168h. I dont feel this unsettled pattern setting in today is necessarily 'locked in', despite the way the Atlantic is being modelled at the moment.

[Frosty.]

I think the models are still really struggling with the persistent cold block to the northeast, it really doesn't look like moving away too far and it could easily come back, as the ecm 00z shows, even the gfs 00z shows the cold block just to the northeast of the uk on december 30th, it's good to see the ecm continuing to look similar to the 12z last night and it does look more and more like next week could see a return of the colder weather with a risk of snow for some, mainly northeast britain but who knows, the lows next week could be disrupted due to the forcing of the cold block and wintry weather could make a comeback, this is not going to be a typical zonal spell with atlantic depressions sweeping through, the cold block still looks as though it will disrupt the lows and after a brief break from cold weather, it could return, I got that feeling after the ecm 12z last night although yesterday's gfs 06z also hinted at it.

[Bristawl Si]

There's a twitter comment from Joe laminate floori that it's showing negative NAO for next 30 days (believe it when I see it!) - hopefully Matt will be along at some point with an update.

And two days ago it was showing mild all the way. Another model for the bin!

[Gavin Hannah]

I agree with Frosty (Edit, I wrote snowdrift as I spotted his name in the list of likes lol..... far too early!)

The question is, will be getting clipped by a succession of Lows through the rest of December, or is the GFS over doing it? It's a game of inches, and Joe laminate floori was def in the ECM camp last night, so, I'm inclined to jump onto the ECM band wagon too.

I've noticed that the LP front is still slowing down this morning. Wet weather was supposed to arrive at my location early this morning, now, the weather forecast is not saying any wet stuff until this afternoon.

Some blizzard conditions for the grampians which is good for the ski slopes.

Having just viewed the ECM this morning, it would be nice to see the ECM flatten everything out just a little bit more. Not liking the LPs reforming out if FI over the UK.

Edited December 14, 2012 by IBringTheHammer

[Frosty.]

Certanily the more logical view but we are cold weather fans and where is the logic in that?! At least it gives us some interest. Has anyone got an example chart where it did track southerly?

Yes there is plenty of interest this morning and a chance of the cold fighting back at some point next week as lows are disrupted, it's not even going to be that mild in the meantime, temps look closer to average thats all and next week could be trending colder and remaining unsettled.

[Frosty.]

As teits mentioned, there is a crucial period between T+96 and T+120 hours where the ecm sends lows southeast and this allows the cold block to move southwest again, so that is the timeframe which will be pivotal to our hopes of cold making a swift return and there is enough interest to have genuine belief that the lows next week will be disrupted in such a way.

Edited December 14, 2012 by Frosty039

[GulberwickWeather]

I agree with Frosty. This cold has been quite dogged and persistent with lows previous to todays being squeezed further south and the cold hanging on especially up my way. "I think the models are still really struggling with the persistent cold block to the northeast," is spot on I reckon.

[snowking]

Any update on the ECM 32 day today?

As you can see, the control run I mentioned last night certainly towards the colder side of the suite, but there is a notable downward spike around the xmas period

Other than that (as you might expect from such a long range NWP output) a real spread of solutions and no real clear signal either way temperature wise

SK

[Gibby]

Good morning folks. Here is this morning's review of the 00z output of the big four GFS, UKMO, GEM and ECM for today Friday December 14th 2012.

All models show an unsettled spell bedding in over the UK today as Low pressure moves in towards Western Britain from off the Atlantic with an active front carrying strong winds and heavy rain NE across the UK with a spell of hill snow for Northern Britain for a time. Following on behind winds will decrease and turn more WSW with showers chasing the rain away from the South and west by the end of the day. For the rest of the weekend and the early days of next week the UK stays under the influence of the steadily filling depression as it drifts its way across the UK and loses it's identity by Tuesday. This means a weekend of sunshine and showers with some heavy and prolonged showers for the South and West but far fewer in the North and East with some longer drier spells. By the start of next week all areas will see some more occasional rain before a drier and brighter interlude spreads slowly in from the West on Tuesday in slightly less mild weather by then.

GFS then takes us through the middle and end of next week with a new area of Low pressure out to the West of the UK with a strengthening SW flow bringing another spell of wet and windy weather spreading NE again over the UK. This also fills as it drifts across the UK by next weekend though maintaining the unsettled and occasionally wet conditions for all. In FI today the pattern remains locked with Christmas Day and Boxing Day looking particularly wet and unsettled days with normal temperatures as the UK lies under complex Low pressure. With little change to end the run with only brief somewhat colder and brighter interludes it looks like a green Christmas still from GFS today.

The GFS Ensembles show a period of normality with regard to uppers and surface temperatures as Low pressure from the Atlantic remains the driving force to the UK weather right out to beyond Christmas. As usual there is plenty of spread between the members late in the run though there is no real trend towards anything reliable cold even though uppers fall back a little later especially for northern locations.

The Jet Stream shows a streak racing across the Atlantic towards Northern France persisting for the foreseeable future, becoming more of a sine wave pattern later next week at a similar latitude, still to the South of the UK.

UKMO for midnight on Thursday sees Low pressure out to the west of the UK with a strong and unstable SW flow over the UK with rain or showers at times in a continuation of generally mild conditions. The heaviest of the rain will continue to be towards the South and West.

GEM today shows Low pressure too out to the West of the UK drifting slowly East and filling through the following days maintaining the unsettled feel before yet another Low drifts towards the UK with rain bearing fronts crossing NE by day 10.

ECM finally also shows Low pressure out to the West drifting East into the UK and extending SE towards Italy later. High pressure is maintained over Russia with a cold Easterly flow over Northern Europe which towards the end of the run pushes the Easterly flow across some Northern and Eastern areas of the UK dragging colder and drier conditions to most areas by day 9 with Low pressure piling up to the West endorsing a cold and windy day with rain and sleet towards Southern and western Britain to end the run.

In Summary this morning the weather looks like staying windy and unsettled with spells of rain and showers across the UK for most of the next two weeks. There are a few indications of a resurgence of the High pressure block to the NE, notably once more from the ECM Operational (though not as good as last night) exerting a limited influence to parts of the UK towards Christmas but there is very limited support for this theory at present with the more likely scenario remaining that the Atlantic will continue to bring further rain and green conditions over Christmas with temperatures close to normal.

[GoonerGregg77]

Get all these lows from the Atlantic out of the way, and let's wait and see if the Atlantic slows as that jet stream dives south, and then the models will see clearly again.

[Tuxedo]

The current set up with a huge concrete block not far away to our east, early winter all make it likely that we will see sudden changes in the T24 -T96. The weather will be leading the models which will be playing catch up.

[WhiteFox]

All is far from lost in the hunt for cold this morning. With the absence of blocking to the north, we need the Russian high to move west to stand a chance of something interesting; the ECM continues to show this as a possibility. Of course, I've said it many times, whilst that high stays relatively close there is always a chance of cold pushing in from the East. Last night's ECM showed possibly the best case scenario, but this morning's is no write off. If the energy from the Atlantic slows enough then there is a possibility of the high to the east pushing back on the Atlantic and creating a battleground somewhere. To me the 0z ECM shows a potential rain/snow event; if the colder air wins then there is a big dumping.

The big problem with this setup is that we are trying to thread a needle with a camel. As the GFS shows, if the Atlantic powers up just enough then we get nothing.

So, certainly no guaranteed cold on the charts (and after last week do we really want that) but there is something of interest. If I was a forecaster my current ending to a tv forecast would be to replace "at least it will be mild" with "at least there is no raging polar vortex over Greenland"...

For Nick Sussex: could we have your summary of the models wrt chances for snow?

GFS: crud

ECM: maybe...

Edited December 14, 2012 by WhiteFox

[snow drift]

Get all these lows from the Atlantic out of the way, and let's wait and see if the Atlantic slows as that jet stream dives south, and then the models will see clearly again.

The models are seeing clearly IMO, it’s just we don't particularly like what they are showing. The ECM, with the lows tracking more southerly, has a chance and the METO have recognised this in their 6-15 outlook. i.e. NE may get hill snow and frost. Gibbys summary is what I would agree with. I have noticed that some would like to see the block to the NE clear off. I would disagree with this. To my mind we will have more chances with it in situ than not there.

[Methuselah]

And just to add the one that everyone appears to have overlooked: the weather - who knows?

[Troubleatmill]

ECM 15 day ensembles toying with the idea of an easterly around the xmas period, very much the few going for it but better than none!!

[Frosty.]

And just to add the one that everyone appears to have overlooked: the weather - who knows?

Yes the weather will do whatever it wants, it has no feelings for our feelings and the models likewise.

[WhiteFox]

ECM 15 day ensembles toying with the idea of an easterly around the xmas period, very much the few going for it but better than none!!

Indeed, and if the Russian high was not there but instead we had a euro high further south then there would be almost no chance of a cold outbreak. I remember in the bad winters some people calling for a reset (as if we could just push a button!) and, on a couple of occasions we got just that: a Bartlett high (or as close to one as makes no difference) and a raging jet pushing from SW to NE. Cloudy and mild in the south and east with occasional (but not much) rain and mild, wet and windy in the north and west.

If we're looking for cold then we stand a higher chance with the Russian high in place than a euro high...