I stopped checking a couple of days ago, but I see they've become even more extreme since then. From the 6z GFS, Christmas Day 850 anomalies in NA - and yes, those are +20C anomalies, the equivalent of +19 or +20C 850s here!

https://images.meteociel.fr/im/14/25947/gfsna_15_204qya0.png 

And T2Ms for Christmas lunchtime / afternoon:

https://images.meteociel.fr/im/69/23886/gfsna_9_204jjh1.png 

For once it won't be a widespread white Christmas out there, and frankly seeing that massive swathe of above-zero temperatures all the way up to Husdon Bay is a bit disconcerting - it's outrageously above average for the time of year.

It remains to be seen what the effect of all that relative warmth spilling into the Atlantic will be, especially as it'll still be cold over Greenland etc. In theory that will fire up the jet on a different track to normal, and I'd hope at least it means an end to these wind storms we've been enduring down here this autumn/winter. It's most unlikely to happen soon enough to save Christmas, though, and it's definitely not going to happen in time to stop tomorrow's gales down here.

This is very true under anticyclonic conditions. The latest GFS op run for here in Christmas Day has t850hPa and t2m values at more or less the same temperature (10-11°C). Very mild but not the “normal” relationship between these two values at other times of the year or with other synoptics. In isolation, a White Christmas is looking increasingly unlikely but I guess there are still 8 days to go!

The hints at a pattern change approaching the end of the year continue on the latest (12z) GFS op run too.

The part that looks very confident is that a deep ridge is going to move across the US. By ~27th its sitting (along with its asociated warm anomoly) in the newfoundland area or the SE Canadian coast. Even though this is 10 days out the models are all very confident this is going to happen.

The least certain aspects are: we don't know much about the communication between this Canadian ridge and Greenland. Will it extend to Greenland, if it does how quickly will that happen. We also know very little about what's going on over Scandanavia at this time. Because there are two completely different options; either the polar vortex has relocated nearby or we actually have ridging there and the tropospheric polar vortex is instead closer to the north pole at that point.

So these uncertain elements will affect if/when cold gets to the UK. But the models do seem to be confident that the potential for cold solutions rapidly increases after around the 27ht with the 27th roughly the middle of a transition period between a zonal and meridonial atlantic.

The ultimate hope is that we can get the tropospheric polar vortex into Scananavia or west siberia and the Canadian ridge to greenland. If that happens we can get a bitterly cold NNerly.

Its unfortunately unlikely, but is a possibility for happening circa NYD.

Would agree. Seems to be a lot of 'wobble' going in in the ensembles at the moment, but those cold anomalies to our near north don't seem to want to shift, and I think it will take the models another few days to work out how those incredible anomalies in the US and Canada will impact the broader north Atlantic pattern down the line. 

This frame really stands out:

https://images.meteociel.fr/im/12/24378/ecmwfna_15_192lth8.png 

That's a 26C anomaly compared to 91-20, and for context if we were to have that anomaly at the same time here... we'd set an all time high for 850s in the UK, and that includes the day we reached 40C a couple of years ago. Absolutely mind-blowing levels of warmth up there in Canada!

Its got to be good for cold weather here into the new year. No dream charts showing up yet but the pattern is still consistent and the deflattening definitely occurs after the 27th.

A couple of charts that may support your theory. Both GEFS and EC seem to be on board for some sort of jarring of the pattern due to those high 850hPa temps over Canada into the new year, with cold anomalies continuing to stay put to our near north. 

GEFS:

EC:

Broader theme the same, if local nuances between both. 

1852-53 Very cold feb

1710-11 Cold Feb

1843-44 Cold Feb

1828-29 Very cold Jan

1857-58 Rather cold Jan, Cold Feb

We are due one then. 😄

GFS Op 00z: LP in northern N Sea giving cool NW-lies at the end of this week, backing strong W-ly for a few days before a reload of LP restores the NW-lies Sun 22nd (cold and stormy for Scotland, not much better further S). HP then moves up from the SW and is well established 1035mb Christmas Day in the English Channel. This continues and intensifies across Europe to Mon 30th after which it drifts S-wards, and LP developing over Scandinavia provides N-lies for a series of glancing blows for Britain.

[unresolved queries; Will the UK HP over Christmas be a cloudy one or by contrast frosty at surface level? Is the average near norm suggested by WX a combination of mild Christmas week and cold New Year? What has happened to the traditional Scandy High? ]

ECM - as GFS

GEFS - temps cool -mild - cool to 23rd, then a week of milder temps for Christmas with good agreement between ens members; mean back to norm by New Year and declining, with an increasing number of cold outcomes compared to recent forecasts. Some rain at first, then mostly dry to 29th followed by modest amounts of rain in most runs. 

Snow row figures: A dusting of snow across Scotland around the 22nd but none for Christmas itself anywhere; chances about evens in the north for New Year, at that time not negligible even in the south .

LOL, that’s one interpretation. What struck me was that the most recent one was over 150 years ago!

Good idea to check that.  Very interesting.

Although, on reflection (and at the risk of being Mr Scrooge), I think there may be two big clues here: the combination of digits ‘17’ and ‘18’.  I wonder what percentage of Januarys and Februarys in those two centuries were rather cold, cold or very cold?

Bah humbug!

(Early January might be a little more interesting in the Highlands, though — GFS op drops towards the bottom of the ensemble.  Totally FI, of course.)

Agree. I don't think those stats necessarily tell us much. We are rapidly reaching the part of the season where people will start looking for more esoteric explanations for why a cold spell could be on the way. Needless to say, that means teleconnections and developments in the stratosphere. Personally, I'll stick to the medium range model output and look at developments to our south as well as north. The simple reality is that higher pressure to the south is a big factor in putting the kibosh on the UK winter.

Genuinely think things are looking very good still for around NYE onwards for cold here.

Looks like it could even end up over Scandanavia. That'l generate some bitterly cold uppers there.

Seems to spin something up that looks like a snow hurricane north of Scandanavia.

https://modeles16.meteociel.fr/modeles/gfs/runs/2024121806/gfseu-6-300.png?6 

Otherwise known as a polar low. Structurally they resemble miniature hurricanes (not having fronts) and they bring very heavy snow when they hit land. (Some have been known to hit the UK in the past, not been any for a while though!)

There is crazy high confidence for this Canadian ridge.

https://modeles16.meteociel.fr/modeles/gens/runs/2024121806/gensnh-31-5-264.png 

Seems to want to extend a wider ridge over as far as northern Europe. Makes sense really as we are more or less on the same latitude.

Where is "here" – what is your location?

The perfect Summer synoptic that rarely show up in June or July when we want it the most.