Can I ask a very quick question please....I've read elsewhere ( someone from the Meto ) about the GFS suggesting a weakened vortex in early December, what would likely result in this for the U.K. please?

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The GFS 06z OP is a thing of beauty in FI, e.g. at T+336

http://www.wetterzentrale.de/maps/GFSOPEU06_336_1.png

http://www.wetterzentrale.de/maps/GFSOPUK06_336_17.png

 

And before then, a lot of cold 'seasonal' weather. Just at the right time for Christmas shopping

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If my understanding is correct, a weakened vortex ususally increases our chances of cold spell during the winter. That doesn't always mean that we will get cold spells though; I seem to recall that we had a fairly weak vortex in place at this time last year but that still didn't prevent the winter itself being another mild one.

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Control is a belter (GFS)

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hopefully the temps will drop in the SE so that we can join in the fun too

I've just added the 30 year (1981 - 2010) mean to the GEFS 850hPa temp plots. Here's the London one.

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Its crackers how much the charts for a weeks time, look like theyre heading back to the way the cold blast arrived last Friday.

I wonder if we will see a couple of repeats of this kind of pattern, each one a little colder?

Just a thought.

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The ECM 00z op was very much at the mild end of the range of outcomes for days 7-10.

Still the cold cluster dominates from day 9, keeping the mean with maxima around 5C.

A marked rainfall episode on day 10 as the active cold front moves through.

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The interesting thing for me about this period of model watching is the trend towards colder at the exact time when days are at their shortest and the seasons are 'catching up' with the day lengths following autumnal insolation. It might just be that we hit the jackpot at the right time for once. Fascinating charts for most weather watchers (with apologies to Ian Brown). 

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06Z GFS serves up a nice locked-in wintry pattern. Lots of marginal battleground snow events in the latter stages albeit the southerners among us are often on the wrong side of the charts as they stand. But the overall pattern is very nice.

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UKMO seems a bit more amenable to GH building on the 12z than the 00z:

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Now that is in alignment with GFS 12Z at same timeframe.

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This problem seems to be with the Canadian lobe of the PV shifting over the to Eurasia side of the globe, to do this, heights have to drop to the north as it moves across. We Often see this before a cold spell, as this is what slackens the temperature gradient across the pond, thus slowing the Jet.

We want this to happen, as the PV will also pull the colder air across with it, and hopefully end up as a Euro trough.

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The UKM backtracking towards the GFS. Good news. 

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By Tuesday PM, GFS12z has built a 1075  HP over Greenland and the -10 850 is knocking on Scotland's door.

Plus, the HP is underpinned by a proper looking LP to the south.

All the cold is draining down the eastern side of Greenland - if this comes off, Iceland is going to be under -15 850s.

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If GFS is to be believed, I think the word is BOOM.
PV lobe dropping into Europe.

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All eyes on that dartboard LP out in the central Atlantic.  and how it interacts with the plunge of what is probably the coldest cold shot weve seen so far this winter in the charts.  Real cold embedded in this shot, this time.

 

 

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Cracking run but heights to the south are still a concern for me.

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Yes, a more encouraging sign for sure.

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Blizzards for some on Friday if this run comes off

Friday at noon is the Holy Grail for snow fans in England.

Proper Channel Low

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Probably the best run so far of this interesting period. a proper full blooded GH.

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