Just been notified NCEP is having major problems and data is being delayed by up to 2 hours at the moment. This will impact GFS/GFSP and GEFS.

Wow. Viewing this morning's output I am struck by the very mild weather in North West Europe being replaced by deep cold in a very short space of time.  Reminds me of the weather in Calgary in September this year.

The synoptics appear to be changing with no settled single pattern on the cards just yet so for cold lovers I suppose it depends if your glass is half full or not.  I think it is still all to play for.

In the medium term though it does look like a North / South split with a potential pasting for Scotland.

I am unable to post much at the moment so Merry Xmas to Brian and all on TWO  

New Year is less than two weeks away. Anyway he says "to New Year" so I assume he means the period from Dec 27 until Jan 1, which is basically from day 8.

I would urge caution when viewing the ECM as it's had a tendency to over amplify blocking around Greenland. I still only see a cold snap before we see a return of the westerly mobile regime we've been accustomed to over the last month, thereafter who knows but the background signals remain positive and primed for cold outbreaks to the mid latitudes. Will Blighty get lucky is another question.

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY FRIDAY DECEMBER 19TH 2014.

NEXT UPDATE SATURDAY DECEMBER 20TH 08:00

THE CURRENT GENERAL SITUATION A cooler NW flow will weaken tomorrow as a ridge of High pressure crosses East over the UK.

MODELS-2 WEEK HEADLINE Remaining changeable with rain at times especially across the North and West. Possibly becoming more generally colder and unsettled post Christmas with some snow and ice in places, at least for a time and chiefly over the North.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Foreecast is for the flow to gradually be squeezed further South than currently lying near or to the South of the UK between High pressure over Europe and  near Greenland and Low pressure to the North of the UK.

GFS OPERATIONAL The GFS operational this morning shows a mild SW flow in the run up to Christmas before Christmas itself turns rather chillier with overnight frost but bright crisp days as High pressure moves over the UK from the West. This then steadily collapses away SE in the post Christmas and New Year period with rain at times in the North and West and temperatures recovering to the mild side of average for many.

THE GFS PARALLEL RUN The Parallel run is less bullish on holding mild weather exclusively across the UK after Christmas alternating spells of it with brighter and colder conditions with night frost but very limited precipitation of a wintry note, even over the North. The run ends on a mild and breezy note with a long fetch SW flow between High pressure to the South and Low to the North.

THE GFS CONTROL The GFS control run too shows a lot of mild SW or West winds across the UK through the two weeks with some rain at times more especially across the North and West. A few brighter and chillier spells are shown too especially early in the period coinciding with the Christmas break.

THE GEFS ENSEMBLES The GFS Ensembles do show the temporary chance of cold weatehr from quite a few members post Christmas with the overlying trend thereafter for the cold to lift out in preference to milder Westerly winds between High to the South and Low to the North into the New Year.

UKMO UKMO today shows the weather turning colder as we move towards Christmas as a mild SW flow early in the week is replaced by a drift into colder conditions with frosts at night and wintry showers over the North and East on Christmas Day.

THE FAX CHARTS The Fax Charts today show a cold front clearing the SE today with a brief chillier NW flow ahead of another broad warm sector especially across the South before finally colder air from the NW drifts down behind a series of cold fronts from the NW towards Christmas..

GEM GEM today shows a colder interlude at Christmas with overnight frosts gradually giving way to milder SW as pressure falls ro the NW gradually developing into a deep centre and delivering spells of gales and heavy rain to the UK on a SW flow late in the year..

NAVGEM NAVGEM's run today shows a chilly Christmas and a weak trough crossing the South could give a spell of rain for a time on Christmas Day before a frosty period develops by Boxing Day under a chilly NW flow..

ECM ECM this morning shows that after a quiet and anticyclonic Christmas with frost by night and cold bright days the weather turns potentially quite wet and stormy from the NW between Christmas and the New Year.

ECM 10 DAY MEAN The ECM 10 Day Mean Chart supports the highest chance being that High pressure will lie to the West of the UK with a trough to the East of the UK supporting a Northerly component most likely over the UK. This supports a mix of cold and bright weather with some wintry showers with the Jet Stream at Southerly latitudes to the East of the UK and higher over the North Atlantic with the UK lying on the cold side of the flow.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS Trends this morning have been watered down considerably in the incidence of cold weather post Christmas and while some cold options are still shown from reliable Ensemble data there is an equal amount of milder weather shown too from our American partners.

MY THOUGHTS I was very careful with my wording yesterday and chose to use the word potential wisely because that is what was shown. Much of the output today has either watered down or indeed removed the risk of marked cold weather over the UK that was shown yesterday and preferred instead to maintain High pressure to the South and SE of Britain. Pressure does rise over the North Atlantic sufficient from some output to at least give a window of opportunity for something to at least try to come down from the North and the ECM Ensembles support at least a period of chilly Northerlies post Christmas though in the transitory period a spell of high winds and rain is probable. GFS today has gone totally Atlantic biased bathing the UK in mild SW winds for much of the time and this is supported from it's ensemble group too on the whole. I'm afraid the problem as I have indicated all the time of late is the Jet profile across the Atlantic post Christmas is not conducive to give us a lengthy cold spell while the flow stays North of an Atlantic High pressure. While the flow does move South over Europe towards the Meditteranean it seems unable to ridge North far enough North over the Atlantic long enough to stop the inevitable collapsing ridge pattern that we have seen all too often. The net result is from GFS that the pattern flattens out entirely with the polar vortex returned to the North and High pressure to the South bringing balmy SW winds and rain at times to the UK. The one thing that has been removed though is the Azores High for now and it seems very unfortunate for the UK to have it replaced by a European version to hinder an otherwise good chance of cold given that the tendency is to want to bring pressure higher to the NW which would otherwise have opened the door fully from the North. However, we have to sit and watch as things unfld over the coming days as things remain far from certain post Christmas. I would strongly urge folks to not take each run literally as there are a lot of wild swings from run to run and model to model currently and while the good charts of yesterday have been suspended for now I wouldn't be surprised if they don't return again over the next few days but I will withold my input until tomorrow morning before giving a more definitive report on proceedings likely up to the New Year over the UK.

Uncertainty after 5 days at the moment ..................hence my comment

have you read the tweet? 

It clearly states 'west country forecast' not 'nationwide forecast'.

Added on to his original comment

W COUNTRY CONT'D Key thing we will be watchful for end Dec are deep areas of low pressure & resultant disturbed weather. A watching brief.

Another big mild outlier from ECM. Not sure why Ops and ensembles are so different at the moment something has to give soon.

http://www.weerplaza.nl/15daagseverwachting/?r=midden&type=eps_pluim

A very good summary again Gibby. This morning's output for the post Christmas period really is all over the place from model to model and only a fool would attempt to make an accurate prediction of how it is going to go. You are quite right to sit back and take stock before making a prediction.

The uncertainty can be summarised in the GFS v GEM/ECM output this morning. Heading into FI GFS wants to build the Euroslug Northwards whereas GEM/ECM erode it making the Greenland High the dominant feature as we head towards the New Year.

Who'd be a weather forecaster in this country eh? 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121906/gfsnh-0-120.png?6

6Z so far

http://www.wetterzentrale.de/pics/Rtavn12617.gif

http://www.wetterzentrale.de/pics/Rtavn15017.gif

A more festive feel to Xmas at least

My recollection is that where we have had prolonged cold spells eg 1947,1962/63,81/82,85,91, Dec 2010 they have all started with an easterly flow driven by a Scandi/Arctic HP.

Once established then the Hp often retrogresses to Greenland.You may well be right that a Greenland HP can deliver snow for all of the UK.However I don't recall the Greenland being the initiator of severe cold spells.   

Atlantic beginning to quieten down. - Been the quietest I've seen it for ages.  Looking at the 06z chart looks like Christmas will be cool and dry. Temps between 4-6c by day and -2c to 0c by night with patchy frost!? - Just my thought.

http://www.wetterzentrale.de/pics/Rtavn19217.gif

Huge temp difference North to South

http://modeles.meteociel.fr/modeles/gfs/runs/2014121906/gfsnh-0-228.png?6

Bing Bloody Go

Big changes in the GFS 6z Op as it heads into FI. The long fetch SWesterly over the UK in the GFS 00z has been binned. Looks to be falling into line with the 00z ECM and GEM with the Greenland High exerting more influence.

Yes. As I said, stormy conditions generally which would apply to the west. 

http://modeles.meteociel.fr/modeles/gfs/runs/2014121906/gfsnh-0-288.png?6

A cold end to 2014

Yep stunning F1 Plenty of snow for all

This is more like a northerly? Hope this stays put!

The uncertainty on the 00z runs was so large from so early on that I was left unable to deduce anything of much use to expand on last night's analysis, apart from ECM being the closest to consistent.

Interestingly the GFS 06z op has suddenly jumped toward the ECM 00z. This seems to be largely down to the low west of the Azores being further west by day 6, this encouraging the focus of high heights to be SW of Greenland which seems to connect with less in the way of high pressure extending back toward Alaska, this meaning the U.S. low isn't pulled back west, which roots the HP in place over Greenland.

A small shortwave low does manage to nip across from SW of the UK, but this works in our favour, helping to erode the Euro High.

What a staggering contrast to the GFS 00z op run. All bets are off!

Meanwhile, the parallel doesn't have the adjustment west of the low near the Azores on day 6, though despite this it does still manage a slightly better focus of high heights SW of Greenland. The 00z was a decent attempt despite losing the split jet over the U.S. at just 7 days range... this run might just manage to retain it at least a little longer as the better focus of high heights SW of Greenland relates to more in the way of a jet undercutting the ridge:

The LP to the west of the UK is in the same place as the GFS 06z has it, but has developed considerably more.

The next few frames show a more southerly track than the 00z had - momentum is in a positive direction here 

The 0Z very clear where it want's to go, while the 6Z is undecided. Like a ball on the top of a mountain waiting to be kicked either way. 

It's a funny old game we play isn't it? These GFS and GFSP 06z runs are more like yesterday's ECM 12z op run because the U.S. low isn't able to force its way into Greenland days 7-9, which was something that really surprised me on today's ECM 00z op run.

Result by day 10:

So yeah... the epic charts are suddenly back. Ties in with the latest Met Office thoughts according to Ian Ferguson.

Will they hang around for the 12z runs or perform the magic vanishing act again?