But the latter stage of the run is shaping up quite promisingly with the jet stream on a slightly more southerly track and a period of calm developing in the Atlantic with heights rising - and still a split PV and a strong Arctic High.

It can pee it down for the next fortnight all it wants, as long as from the 15th day we get snowmageddon. 

Well, not 'snowmageddon' but most people should be encouraged by the picture at the end of the run. Arctic High, split PV on our side of the NH, weaker southerly tracking jet and the high pressure to our south back where it belongs, displaced south of the Azores.

Despite the charts, unless the Azores high really muscles in or parks up close to the UK...there is still hope in these models of a return to something wintry.

Models incapable of picking up a true u turn in current patterns.If this had been 1962 now bet charts would have been similar and if any did predict a snow fest would have just been lucky..

If this had been 62 the odds would be slightly more favourable regardless of what the models were showing. The dartboard analogy is a good one. To an extent I can understand why people question the causes. What I don't understand is why they are questioning it is happening. There's no doubt in my mind that it is real. Very real indeed.

Jetstream tracking south of the UK through to Fri 25th, strong at first but weaker later. Even when disrupted by a loop working through (e.g. Mon 14th, Wed 23rd), it soon returns to this trajectory.

GFS - UK affected by series of weak troughs coming in from the Atlantic as LPs out to the west fill on their approach to us (see Fri 11th>Sat 12th, Tue 15th>Wed 16th, Mon 21st>Tue 22nd). Yesterday's strong development of HP a week before Xmas has disappeared and the suggested easterlies at the end of the run still remain just that, tantalisingly. So no stability in any medium term prediction.

GEFS - temps fairly close to seasonal norm throughout, a few brief mild bumps at first, slightly cooler towards end (Fri 25th). Not dry for any length of time, highest chances of rain around Tue 15th esp towards SW but not dramatically so.

ECM - troughs tend to be deeper and closer than GFS and at end of run Sat 19th one sticks around NW Scotland as a well-defined depression.

So we have the NWP advertising the -ve AO fairly clearly. The set-up knocks out one of the central pillars of zonality - the jet barrelling to the North of the UK between Iceland and Norway, so there is going to be interest and potential in the outlook.

However, cold spells and certainly cold spells in the modern era are all about timing and a trigger low. The persistence of heights to the East is a blocker to systems progressing through Europe and potentially 'opening the door' to colder air from the North/North East. The opportunity can only sustain for so long before changes upstream come into play and the chance has gone.

Two steps forward and two back this morning. HLB still there but the Atlantic seems to be firing up as well. Making things more complicated.

Sorry guys, as soon as I post anything optimistic, old Pete T comes a-knocking. Best I abstain until the models come back round. 

All academic at that range but the latter stages of the GFS op would probably bring a lot of snow to parts of Scotland, with cold air in place and Atlantic systems running in to but not through the block. 

ECM looks seasonal to my eyes, chilly and unsettled with frost where clouds clear overnight, depending on the strength of the wind. The Atlantic only really gets as far as the UK on the Op run, with the jet far enough south to keep the UK in the cooler air. 

It's certainly not a typical zonal pattern but equally it may as well be from a proper cold POV if we just sit in chilly, wet nothingness and any northern blocking is too far away to properly impact us. 

It's not a terrible place to be I guess with potential for something more interesting at least.

Good summary. It's quite an strange/unusual set up very close to something genuinely very cold and snowy but also it could easily be as you say coldish wet nothingness. At least we seem to have a ticket to the game this year though.

GEFS 00z 850 spread for London in the week leading up to Xmas.

https://www.theweatheroutlook.com/premium/gefs-tables.aspx?run=00&fv=tmp850&loc=London&lat=51.5&lon=0&p=&cty=

That's a very clear way of presenting it. Around average with a small risk of something colder and perhaps trending a little cooler toward the big day itself.. 

When I first looked at it, I got very excited until I spotted that the temperatures were the 850's as opposed to the 2m's.

You too?

I was going to say - 63% chance of it being between -4c and 0c isn't bad for Xmas eve!? BUT OH so frustrating it's the 850's.

I disagree on several points, Ian.

First, it is not about timing or trigger lows any more than it has ever been.

Second, the persistence of high pressure to the East is a common feature of winter synoptics: it's about that balance between the jetstream and the block.  Nothing can change  geography: we sit with a warm ocean to the west and potentially cold land mass to the east.

It has always been the case that we need the jetstream to play ball to get sustained cold to our corner of NW Europe.  The underlying climate change signal is making the odds slightly worse with the passing of time but that's it.

FWIW here is the range of max 2m temps across all the GEFS members for Christmas Eve for a spot close to my location in central Southern England:

Meteociel.fr - Tableaux GEFS v12

 Sorry I took out the table because it was breaking the formatting. The TWO equivalent is here:

https://www.theweatheroutlook.com/premium/gefs-tables.aspx?run=00&fv=tmp2max&loc=Berkhamsted&lat=51.5&lon=-0.5&p=&cty=

Thanks, didn't know you had this functionality on TWO now, I will bookmark it.

Hope that the 06Z GFS run isn't too representative of the ensembles though 

moi aussi 

The GFS op runs are fluctuating run to run as you would expect. However the ensemble means have been rock solid for a while with a cooling in 850s as we head towards Christmas. 

So nothing too spectacular in terms of an outlook at this stage. The set up is finely balanced though and it wouldn't take much to change the outlook, e.g, a subtle change in the direction or strength of the jet.