18z has put a hell of a block in the Atlantic 

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Consistent in the -10 upper air isotherm getting just about to Scotland, and the -15c one staying north of Iceland at best. With -7 the best on offer for the south. I remain sceptical.

An impressive wall of High Pressure, text book block, but Im afraid, Must try harder.

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Synoptically, 18z is just insane. Absolutely insane.

It just goes on and on and on. 

http://www.wetterzentrale.de/maps/GFSOPEU18_213_1.png

I agree with WI that in an ideal world, the uppers would be colder, but these are fine details most definitely subject to change. 

http://www.wetterzentrale.de/maps/GFSOPEU18_213_2.png if this pattern locks in we’d damn well know about it. 

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18z is a good old fashioned pub run. Something we rarely see in a modern winter 😁😁😂😄

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Seems I spoke too soon - this IS cold.

http://www.wetterzentrale.de/maps/GFSOPEU18_222_1.png

http://www.wetterzentrale.de/maps/GFSOPEU18_222_2.png

 

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So in short significantly colder than average for the time of year. T850 average here is about -1°C for the start of December. The GFS 18z run had the t850 values running at over 5°C below that for quite a period.

I guess if you compare it to 2010 it may be disappointing but so will 99% of Decembers.

Compared with the last 25 years here as a whole it looks cold and increasingly persistently so. http://www.wetterzentrale.de/maps/GFSOPEU18_231_1.png 

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The UK would take a winter battering from the 18z infact if the daily express did GFS runs this would be it-

All to be expected with the stratosphere about to collapse into a reversal of 10MB winds...

I have to say I’m amazed some aren’t buzzing with the 18z it’s cold and from d7 onwards it’s very chilly 

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850 temp deviation for mid next week. 

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I think people are cautious given we don’t really have the MetO on board. 

http://www.wetterzentrale.de/maps/GFSOPEU18_144_1.png

http://www.wetterzentrale.de/maps/UKMOPEU12_144_1.png

Significant differences at T+144 and not to be discounted. 

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Well the Beeb are talking of another Northerly after next weekend Joe 

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If you are asking me would far rather be looking at a wall of high pressure to our west bringing the most sustained period of Arctic air in winter months for many a year, than looking at some crud-ridden jet driven succession of Tm Pm air, then yes.

I am concerned that given that we have already had 3 northerlies (12 Nov, 19 Nov and 25 Nov) with effectively 2 more to come, with the fifth being the best thus far by the looks of it, that we would have seen a bit more snow and had some colder uppers.  I am concerned that northerlies are becoming enfeebled due to reasons already stated by myself, Darren and Gusty Steve, which, if it is the case, is a shame. I'm not comparing to 2010.

 

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Doesn’t mean much to be honest Marcus.

I will not relax until we have cross model agreement. 😊 MetO has been known to be correct over the other two before - hopefully not this time. 

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Very impressive 18z....and the extended JMA looks very wintry

http://www.meteociel.com/modeles/jma/runs/2017112612/JN264-21.GIF?26-12 

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Rather it was mentioned in forecasts than not at all , it certainly shows it as a possibility. 

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I’m concerned that cold synoptics in autumn are being dismissed when northerlies are normally at their most potent in February. I think expectations are unrealistically high for the time of the year. I am in a prime location for a northerly setup and I recall very few potent cold ones at this time of the year. What the models show is impressive warmer than average Arctic or not.

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If only it was end of Dec/Jan or Feb this (set up) could be way more colder and snowy right!??

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Yes of course it may well be correct but it is very much on its own with good consistency among the other models. If it calls this one right then I think it should be the “go to model” in future modelled cold spells.

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Aberdeen had some snowy weather end of Nov 2008 - I remember watching rugby on TV (Scotland against Canada) and it snowed during the end of match in Aberdeen - can't remember if it was a northerly or not!? But it's similar to this sort of set up if I recall. 

It has been a while since we have seen or will see this level of cold and wintry weather in November. 

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Can go the other way of course but this far out that bolt of cold air in the reload may be overcooked with higher temps progged at this time. Wouldn't take those temps as gospel and we could lose a few degrees in model fine tuning as we get nearer.

I don't think you can say that. Each model sometimes performs well and sometimes performs badly. Given that the atmosphere is chaotic you will never have exactly the same situation in future so just as with investment funds "past performance is not a guide to the future".

Of course cynics would suggest that if you choose the model with the most boring outlook for the UK you won't go too far wrong, but the odds are against the UKMO solution IMHO. 

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I think we forget that we rarely see potent Northerlies anymore - As the basis for potency is getting the cold from a High enough lattitude & that its direct In its attack on the UK -

What we are used to is modified Northerlies taking cold air From southern Greenland & Iceland with a longer sea track-

should the 18z land then -8c over Scotland from the eastern greenland shelf will be enough for ice days & deep cold - even in Aberdeen !

plus it will be winter then !

Fair enough Rob. It (UKMO) is definitely in the minority so if it does get the situation right then I’d be interested to know what it has picked up on that the other models’ programming had not factored in. (Excuse the oversimplification of my terminology).

I judge each of these situations as a learning experience and whereas the majority do not come to a wintry conclusion some do and that’s what makes it all so interesting IMO.

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Well it looks as though my hopes of mild, grey conditions for cycling are to be dashed.

For me the form horse year in, year out is the ECM and as long as that is 'on board' then so am I. The transition from 216 to 240 is to be taken with a pinch of salt, that sort of 'bomb' off a shortwave you can't possibly know at this distance.

Thankfully I have thermals to tide me over, felt toasty in them this afternoon.

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Interesting 12z ECM ensembles for London:

Solid agreement out to day 5 then some uncertainty through the reload phase and then the cold cluster dominates once again from day 10/11.

Impressive mean and a few ice days.

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