So where's your money Brian 

Looks fairly evenly split to me, for the far south. I'd say 8 "mild", 9 "cold" and one "average", depending on your exact cutoff points.

https://www.wetterzentrale.de/maps/ECMOPEU12_240_2.png 

And the longer this region stays cool, the easier it will be for deeper cold from the Pole (or imported from the northern continents) to push further southwards as we get deeper into the winter, should the broader Atlantic pattern allow, that is.

No above average heights (yellow) over Greenland like in yesterday's allowing LP to take a more northerly track. 

I’m still a bit puzzled as to why such promising signals have eroded over just 24hrs, but the weather has a tendency to puzzle and amaze.

The thing that puzzles me is why the models so often seem to be wrong on the cold side rather than wrong on the mild side. They rarely seem to undercook a cold spell in advance, it always starts extreme and then gets watered down nearer the event (albeit sometimes with a wobble back towards the more extreme solution at the last minute).

If I had to hazard a guess it's how the models are resolving each little pulse of the jet. Step 1 underplay and have a nice clean cold evolution, Step 2 overplay and have a mild and wet solution, Step 3 move back towards a cooler solution by reining the jet and LP development back somewhat. Then move to step 1 again for the mid/long term pattern etc.

TBH looking at the ECM ens earlier they're a little worse than last night with more mild scatter 26/12 to 30/12 but not majorly so, the Op went milder this time post Xmas and 24th and 25th are now more resolutely showing mild than they were. I'll await tonights effort with interest.

That said I'm inclined to join you in your pessimism, at least for down here. It just has that look of the jet being a teeny bit too strong and not quite aligned well enough to allow the blocking to affect the whole of the UK. 

looking more and more that way - some epic charts seen over the last week though been fun chasing that. I suppose it could always change back - what is it that’s said models always struggle with blocking and FI is 48 hours when it’s going wrong!!

Agreed.

What seems to have happened is that the jet stream has reinvigorated and stopped looping; that in turn has cut off the warm air advection which was sustaining the upper block.  Then the vortex seems to have reorganised and closed in on the pole, which - as you observed - has squeezed away the upper block with remarkable speed.

Without the high latitude blocking and with the resurgence of the high pressure belt to our south, the result is almost inevitable.  The northern half still looks to get several days of cold and wintry weather but from the Midlands south that looks like it this time around.

But it is a puzzle how it can mostly melt away in 24 hours.

Agree. They are always correct when the models forecast mild but when it comes to cold weather it always starts off exceptionally cold and downgrades or flip back to mild.

We have this comment and debate every year! As the models are just algorithms to try and make an accurate prediction you'd think there would be a correction factored in for the last twenty years along the lines of "the tits up last week adjustment" 

Frankly, I'd settle for anything in the models now that doesn't produce another two weeks of constant sunless drizzly grey dross.

Models will always be more accurate predicting colder weather in the spring our new winter...Dec and Jan are becoming extended autumn months( although always be exceptions..be good to see a cool wet September but never happens either....

I assume Pattern matching or some such jiggerypokery

A point I would make here is that if the pro forecasters are still rather unsure about what happens on Christmas Day, then how can the rest of us be anywhere close to sure as to what happens from that time onwards.

As has been said already more than once in this thread, the models are in a state of considerable volatility at the moment and thus reliabilty at even relatively close range is likely to be lower than it would be normally. I seem to remember that the models had a similar wobble 2-3 days ago to the one they have had today. Only my view, but there could well be more twists and turns yet.

I don't know whether this is relevant, but teh closest match on the TWO analogue index usually has an index value of around 9,000. Today the closest match is 1967, with an index value as high as 11,143. It suggests that the current set-up is something of an extreme one for the cusp of the shortest day, and might explain why the maths which drives these models is churning out varying results by the hour - we're close to the edge of what is possible in weather terms (odd synoptics and close to the shortest day).

Agreed it has been exceptionally grey this month so far. Don’t think I’ve seen the sun for a week. 
Wonder if I’d get planning permission for a 2,000ft tower in the back garden. 

Good spot. You are right that the index value is unusually high and today's No 1 quite often would not make the top 10. 

ICON18z moves the cold south.

https://www.wetterzentrale.de/maps/ICOOPEU18_120_1.png 

I'd probably go something like 60:40 in favour of a fairly average or milder scenario predominating from the middle of the coming week with the exception of a few colder days around 27/12. I don't ever bet on anything, but gut feel remains for an anomalously cold period in late Jan or the first half of Feb. 

Beat me to it Q. It’s a subtle but tangible shift in ICON in keeping noticeably more robust heights over Greenland at 120.

Might be nothing, but at least it’s stopped the rot.