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

[Frosty.]

Well, now Gibby has jumped off the fence into the cold camp, it adds even more credibility to what the models are showing, I feel that today is the tipping point and now it's just a case of how strong will the easterly blast be and how cold will it get, are we looking at a potential Jan 1987 rerun that lasts longer, since that frigid spell only lasted 4 or 5 days.

[Ian Brown]

That's a very good set of ensembles, if you look at the T144 position, the OP is a solid run. Some members bring in an easterly quite quickly (at least for De Bilt) but note how many go pear shaped later on with a perceived bringing back of the Atlantic. Literally just 2 members.

JMA is certainly not interested in an easterly tonight!

http://www.meteociel...?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.

If you view it on wetter, I would suggest a T216 or T240 would see a looping of the UK High with raising heights to the NE.

Edited December 3, 2012 by Ian Brown

[bobbydog]

That's a very good set of ensembles, if you look at the T144 position, the OP is a solid run. Some members bring in an easterly quite quickly (at least for De Bilt) but note how many go pear shaped later on with a perceived bringing back of the Atlantic. Literally just 2 members.

If you view it on wetter, I would suggest a T216 or T240 would see a looping of the UK High with raising heights to the NE.

blimey ian, have you just come out of the closet? from narnia!

[If Wishes made Weather]

My apologies in advance, but I’m going to ask what is possibly a incorrecly premised set of questions, but perhaps the experts can assist?

At a very high level (excuse the pun) as I understand it, we see a variety of signals indicating northern blocking, which, in its generality, will almost certainly amount to colder conditions than were we to see signals for patterns drawing air from, say, the south west.

At the lower level, we have the models. We are told that the models - at least in the latter stages of their runs (+144 onward) are so vague as to be useful at best of a confirmation of the pattern suggested by the more teleconnective signals.

Weather - the stuff we get and feel on the ground – is only predictable and can be shown in the models at perhaps a period of 96 hrs and less, and then, particularly with precipitation, then even 12 hours is safer.

But where is the connection between the reliable part of the model run, and the indications shown in the longer term?

Like many on this thread (but I recognise not everyone), I would enjoy -8 upper temps and significant dentritic snow coming in from the East. What I don’t really understand though is where this - or any other weather – should come from if it isn’t, at least in its pre-form shown in the +144 areas of the model runs.

For example, tonight’s ECM shows something like this for the 13^th December. Surely, it should show this tomorrow, also for the 13^th December – possibly with some modification, but obviously be 24 hours nearer. But time and again over the past month or so, this sort of weather has been shown, but never moves into the near time. How can it then suddenly disconnect, and suddenly appear again in the 96 hour timeframe, without being evident in the space in-between?

[Weathizard]

ECM ensembles are fantastic and they are why we all need to look into more details of each run rather than take the op as gospel. Hope the GFS continues to shows this theme later on, by this I mean a continuing trend to cold and maybe and op and control tandem easterly run.

[Summer Sun]

Looking through this thread and I'm quite positive for a cold spell with snow for some, yes its not 100% perfect but it could be much much worse at this time of year

Let's compare the 4th of December this year to that of 2010

OK not the snow of that day but it will be cold again with further snow showers in Scotland its certainly a more positive way to go than 9 years ago

As I said it could be much worse think back to 2003.......................

Keep positive folks and snow will arrive

Edited December 3, 2012 by Gavin.

[Thundery wintry showers]

If you view it on wetter, I would suggest a T216 or T240 would see a looping of the UK High with raising heights to the NE.

Indeed- between T+168 and T+192 we see a build of pressure over Greenland and Scandinavia which would render a subsequent evolution to an easterly type quite plausible.

The ECMWF 12Z run at around T+120-168 is quite reminiscent of tonight's UKMO at T+144, which on the face of it looked a bad chart for cold/snow lovers- the key to the evolution is the way that the advancing Atlantic low stalls against the rising heights to the NE and ends up filling and drifting south-eastwards. I often use trends in the ECMWF ensemble mean for general guidance and tonight is the first time that I've seen a pronounced east to north-easterly flow showing on the ensemble mean.

The one caveat with easterly types is that if the Scandinavian high sinks southwards we could end up drawing in a dry cloudy SE'ly type instead, but so far the longer-term signals have been pretty consistent in suggesting an east to north-easterly type which would be highly likely to bring wintry showers (snow inland, marginal near the east coast) well inland off the North Sea. With it being so far out, though, I'm still stopping short of calling it nailed-on- in particular the trigger low next weekend will be absolutely crucial.

Edited December 3, 2012 by Thundery wintry showers

[chris55]

Well, now Gibby has jumped off the fence into the cold camp, it adds even more credibility to what the models are showing, I feel that today is the tipping point and now it's just a case of how strong will the easterly blast be and how cold will it get, are we looking at a potential Jan 1987 rerun that lasts longer, since that frigid spell only lasted 4 or 5 days.

That was probably the coldest easterly ever recorded!!!! At least in the last century (WRT uppers) Aiming quite high there!

[Frosty.]

Blimey, that is cold.

Just like the Ecm ensembles

Since it's only really just over a week away and with such massive ensemble support, surely it's unlikely to go pear shaped.

And in the meantime, snow showers this wednesday and risk of sleet or wet snow on thurs/fri, especially but not exclusively for the north, things could really accelarate towards a very wintry outlook now.

That was probably the coldest easterly ever recorded!!!! At least in the last century (WRT uppers) Aiming quite high there!

I like to set the bar high, I think this upcoming cold spell will last a lot longer than in 1987 with even more snow.

[The Giant Daddy Jackpot]

Well, during the last couple of weeks or so the models just could not hit the nail on head for a trend to sustained cold but I think in the last 48 hours that trend is coming into focus and the odds are shortening for a sustained cold period without a western jet intervention.

I feel that most here are confident of an easterly flow by next week and strong signals of a Siberian blast as a Scandi High looks likely. I won't stick my neck out for lots of snow but very low temperatures looks on the cards.

Edited December 3, 2012 by Sussexwalker

[chionomaniac]

UK4-extended PPN type discrimination for Weds 06z (shown here with neutral temp bias) continues to emphasise patchy snow potential Midlands into Cotswolds / Chilterns etc as occlusion moves south. Ice threat post-front onto some very low RST's is of arguably greater concern, as skies readily clear.

Love that chart Ian! I would love to see it showing powder snow in an easterly!

Also it seems to be missing off snizzle on the chart!

[IDO]

Well as we know the NH is in a blocking pattern and has been for a little while. Siberia and Canada/Alaska have extreme cold forecast for the next 10-14 days. The question is can we grab some of the action before the AO weakens.

The following are 2m temps NH view:

http://www.meteociel...ech=204&carte=1

Run the sequence and see how the -28c temps move from Russia westwards. It takes the whole 16 days for sub-zero temps to breach our Island. The floodgates would then be about to open. Nearly half of December to wait before the frigid cold comes (on this run), over 50 GFS runs and a lot of shortwaves.

If we do miss out this December it will be a big big miss. The potential for cold and snow, as no doubt Canadians will be testifying to in the next few weeks, is enormous.

Do you feel lucky?

Edited December 3, 2012 by i'm dreaming of...

[SMU]

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

YESSS how often do we see the -25c Scale!!!

S

[chionomaniac]

Not bad - first extended ice day average ensembles from day 10 until the end if the run.

[fergieweather]

Love that chart Ian! I would love to see it showing powder snow in an easterly!

Also it seems to be missing off snizzle on the chart!

We've especially loved it during the past summer when it showed 'large hail' signal alongside UKMO's tornadic parameter modelling - but that's another story for next year's warmer months!

[bluearmy]

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.html

into the freezer. defo an easterly flow but what will the troughing be like to our south ??

[Backtrack]

UK4-extended PPN type discrimination for Weds 06z (shown here with neutral temp bias) continues to emphasise patchy snow potential Midlands into Cotswolds / Chilterns etc as occlusion moves south. Ice threat post-front onto some very low RST's is of arguably greater concern, as skies readily clear.

What happened with the risk of wintry ppn running into southern parts of north west England, Ian? Has there been a southern shift since the last update or is this chart for a latter time frame when it's already moved away?

Cheers.

[Isolated Frost]

Absolutely top notch ECMWF ensembles today- watch the trend... the NWP will set in place, this could become v v v interesting...

[fergieweather]

What happened with the risk of wintry ppn running into southern parts of north west England, Ian? Has there been a southern shift since the last update or is this chart for a latter time frame when it's already moved away?

Cheers.

03-06z frames retain it (in modified NAE)

Edited December 3, 2012 by fergieweather

[Timmytour]

Is there any relationship between the fact there is a super typhoon, just hitting the Philippines, on a far more southerly track than normal and the current "unusual" set up we are seeing now? Is it possible the ultimate track of that typhoon could act as a butterfly and change the models perspective of what happens on this side of the hemisphere, or is the correlation slight or non-existent?

[Frosty.]

A typical reaction to those stunning ecm ensembles, and it's almost within the reliable timeframe, holy smoke I can't wait for the 00z now.

[Ice BIast]

http://www.knmi.nl/e...agse/index.html

YESSS how often do we see the -25c Scale!!!

S

....That is ridiculously good! Plenty of very cold runs there.

Frosty's animation is perfect for this situation.

Edited December 3, 2012 by lce Blast

[Backtrack]

This NAE WBFL / PPN type sequence tells the story we're plugging for now (and that's all I'll post for now!):

Liking the look of that, shows a brief window of wintry PPN for those of us in the mild(er) west!

Thanks Ian.

[jessandjon]

This NAE WBFL / PPN type sequence tells the story we're plugging for now (and that's all I'll post for now!):

So is the Devon an Cornwall bit in for much or not

Edited December 3, 2012 by jessandjon

[Continental Climate]

the 18z coming out and hopefully we can get some more charts like this in the +384 range this one screams potential http://www.wetterzentrale.de/pics/Rtavn3841.png