Gfs all over the place just look at those ensembles again!

Much better GEFS this morning. 

GFS then going for a few days of cold northerlies between Christmas & New Year with a Channel Low?

I'm in Nottingham with family 21-28 Dec then the drive north back to Edinburgh for Hogmanay. Could be an interesting festive period!

At least it's not back to a SW flow yet

Big differences between the big 4 for Christmas. This is excellent because at least it keeps the show on the road for a while longer. 

00z ECM, GFS, UK Met and CMC for 00GMT #Christmas ECM and UK Met are the best if you're hoping for snow in the southern half of the UK. pic.twitter.com/hL0FeSNoFO

— TheWeatherOutlook (@TWOweather) December 18, 2021

Quite a turn around because previously the models were fairly keen on a cold spell over Christmas and then a quick warmup. Now it looks like the leak of any cold will be closer to New Year.

How exciting is all this !

This is the mean for Chtistmas Eve. Its very representative of the synoptic set up.

https://www.meteociel.fr/modeles/gefs_cartes.php?ech=144&code=31&mode=0&carte=0

And these are the mean 850's. Remember that assuming we get that undercut and a SE'ly flow -2's would be enough to deliver the goods.

https://www.meteociel.fr/modeles/gefs_cartes.php?ech=144&code=31&mode=1&carte=0

Its trended a little further south and it is all very very poised for the best run in since 1978.

Have car, will drive 

Yesterday I heard the word 'battleground' used in a forecast for the first time this winter; battlegrounds are messy and unpredictable places. BBC last night showed the cold/mild boundary to be later in the coming week from NI to East Anglia

WX summary: the Atlantic wins out and W Europe becomes milder over the next two weeks, with a little holdback over the highest ground in Britain; but the very cold air in the far NE becomes more widely established. A dry week 1 is followed by a swathe of pptn from Spain up to the Baltic and including Britain

Jet - not much action around the Uk until Wed 27th when strong W-ly over France breaking up and moving further S by Sun 2nd

GFS op - current HP and its follow-on ridge (as before from  Iceland to Greece) collapse by Thu 23rd leaving Britain in col between LPs in Atlantic and Baltic. The Atlantic one breaks the stalemate moving to UK 965mb NI Mon 27th eventually merging with the Baltic one and bringing in a spell of (not very exciting?) N-lies to Sat 1st after which a broad area of shallow LP over Britain with a noticeable temp gradient N to S. (to my eye, the final evolution looks unstable)

GEFS - mean temp descending to norm Tue 21st then cooler from Mon 27th (Scotland & NE England straight down to cold on the 21st). Very little agreement in ensemble from as little in the future as Thu 23rd; control & op amongst the mildest to Mon 27th and then switch cold or v cold over New Year. Pptn quite general from Thu 23rd, snow row figures high teens in the N/NE, negligible in the S

ECM - diverges from GFS after Fri 24th with any prospective N-lies being diverted out into the Atlantic by a series of not very deep nor very mild LPs running across England.

Xmas prospects look white for the N/NE and green for the S

https://www.wetterzentrale.de/maps/NVGOPEU00_168_1.png 

This is just 25/26th. After that is when the real fun begins.

Glass half full analysis, but very worthy for it.  Those looking for a white Christmas need to look for the ridging to the north to strengthen and hold fast around 24th/25th rather than bend and allow the approaching LP to billow northeast.

The angle of attack of the Atlantic trough needs a WNW-ESE tilt.  The 0c 850mb isotherm needs to be south of the south coast,  These are the things needed to bring the far south in with a shout - I think at present the M4 looks like being the old classic snowline. And then of course the risk of a lack of precipitation except in the far SW....fine margins

But lots to play for and it could go either way.  Fun watching the twists and turns anyhow.

Indeed Phil. This is the line I'll be watching very closely in the run in. 

LOL. It is just a perception: it’s the same model software and the same data capture process.

But we are approaching the infamous ‘data shortage season’….

I honestly think for more Uk wide interest the main shift today is towards new year, Once the transition has taken place later this week.

Yes, good summary.  A slight reversal of the trend in the overnight runs; something that was always a good possibility.

In addition to your commentary, the option of energy pushing the LP east of the prime meridian would also tick the box. This has appeared as an option in recent output.

Unless there are more lurches in the models the battleground area means the set-up for Xmas Day will remain unclear until after mid-week; maybe even Xmas Eve.

https://images.meteociel.fr/im/52/13891/animjux7.gif

The Meioceil GFS video gif in the FI end of the run, shows a similar breakdown to the classic 1947 scenario, with a strong east west jet to our south and low after low zipping along the channel and then a little higher (m4), each time depositing a 1979 blizzard as it engages the cold heavy weight air modelled to be sitting over the UK.

How we got there - is also (and perhaps) more interesting: After the initial Christmas battle of the air-masses (as quoted by the BBC forecasters), the cold air loops around a shortwave feature and smothers the UK from the north, leaving us in a quiet and in places wintry shower world calm before the storms - as the Atlantic resurgences to our south, as described above. - to deliver the dreamland snow-maggedon. Of course most of this is still a scenario of the models that have flip-flopped between scenarios. Like a candle in the wind.

I’ve looked through the P’s on the GFS and the 0 to -5 isotherm is straggled across the UK on many runs , some have it down the S Coast which would be cold enough for snow widely

Most have it sat around Lake District to Newcastle

Certainly colder on the 00z than yesterday evening

These charts are very telling. They are the GEFS projected 2 metre temperatures for Folkestone, Birmingham and Glasgow

There is generally good agreement for the cold to be in place from the Midlands northwards but huge uncertainty across the south where there is generally a milder bias presently. Glasgow goes into the freezer.

Folkestone

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=49909&model=gfs&var=5&run=0&lid=ENS&bw=1

Birmingham

https://www.wetterzentrale.de/en/show_diagrams.php?model=gfs&lid=ENS&var=5&bw=1&geoid=50902

Glasgow

https://www.wetterzentrale.de/en/show_diagrams.php?model=gfs&lid=ENS&var=5&bw=1&geoid=49838

GEM and UKMO are more aligned to yesterday's scenario of the battle of the air masses - and each has a different view of the location of the border between the cold and mild air, the ECM being further south, with the hint of undercutting channel low potential earlier than the GFS model - which delays the battle via the short wave intervention.

Very obvious direction of travel in the ECM ensembles this morning. COLD!

https://www.meteociel.fr/cartes_obs/ecmwfens_display.php?x=317&y=140&run=0&type=10&runpara=0

It looks cold from Birmingham and probably cold enjoy for snow from Birmingham from 24th , albeit could be messy

Glasgow already very cold by this point and snow highly likely falling in any precipitation 

Folkstone probably more around the late December average 

i know, tongue-in-cheek and yes the airplane data will no doubt come up!