Sign of things to come from around 28th Dec then the real colder weather kicks in just before NYE:

5 days later this:

Met Office have been talking of a colder spell to develop from early January.

One model - subjectively known for it's erratic behaviour past +240 - can not be taken too seriously. You might just as well hand-pick the odd blocked chart from the GFS suite.

One thing I can say for sure is the MetO don't base their forecast on the extended range of one run of the CFS

On earth in the fringes of Western Europe and it's again more of the same up to Christmas. Fairly mobile, westerly pattern with a hint of something dryer and quite mild at times.

Euro slug firmly in place for the foreseeable. All this talk of a pattern change appears to be just that ... talk.

We all know what happens once the euro slug gets established and how difficult it is to get rid of the pest! It just sits there for an eternity, wrecking our winter prospects.

Too far off! I don't belive it!

Doesn't look cold to me! GEFS look more interesting.

http://www.theweatheroutlook.com/charts/gefs/gefsens850london0.png?cb=50

A few runs starting to skirt with the -10 mark late on

HERE IS MY LATEST ANALYSIS FROM THE OUTPUTS OF THE WEATHER COMPUTER PREDICTION MODELS FOR TWO WEEKS FROM 8AM TODAY MONDAY DECEMBER 15TH 2014.

NEXT UPDATE TUESDAY DECEMBER 16TH 08:00

THE CURRENT GENERAL SITUATION A slack and rather cold West or NW flow will back SW tomorrow as a warm front approached the West of the UK later tomorrow.

MODELS-2 WEEK HEADLINE Remaining changeable with rain at times especially across the North and West. Temperatures generally close to or a little above average but colder periods over the North when showers could turn wintry.

THE JET STREAM ENSEMBLE FORECAST The Jet Stream Ensemble forecast continues to show the flow weakening and meandering North and South in the vicinity of the UK over the next few weeks. It's trend though will be to edge first North a little and then back South through Week 2.

GFS OPERATIONAL The GFS operational this morning shows a continuation of the Westerly flow through the next 5- 7 days with rain at times and further wintry showery incursions across the North. In the days that follow including the Christmas period a Westerly flow looks the most likely option with any colder air resticted towards the North where some wintry showers could occur over the hills while there will be spells of mild and damp weather with rain at times across the South. Late in the run deep Low pressure is shown close to the NW with rain and gales across all areas followed by a brief Northerly incursion on the rear end of the depression as it moves away East. Otherwise temperatures will be largely maintained close to the average for late December.

THE GFS PARALLEL RUN The GFS Parallel run as one would expect in the short term very similar to the operational in theme while later in it's run there is much more influence across Southern Britain from High pressure to the South with a lot of dry and benign conditions developing with patchy frost and fog in average temperatures. This is shown to have a knock on effect over the North too with less colder incursions from the NW and more mild and rainy SW winds instead away from the far North and later NE.

THE GFS CONTROL The GFS control run is different in the aspect that High pressure albeit a small cell breaks this Westerly pattern towards Christmas as it drifts to Scandinavia from Scotland and intensifies later over Europe. This sets up a block there and brings the UK under mild SW winds with the Jet flow unfortunately for the UK riding over the block over Europe and keeping any cold air harmlessly away over Eastern Europe.

THE GEFS ENSEMBLES The GEFS Ensembles members show a concoction of different options this morning ranging from mild Westerlies and various other options including Northerlies which could bring colder weather to the UK. However, the general theme is for a Westerly bias to be maintained towards Low pressure to the North and High to the South albeit weaker in structure than of late.

UKMO UKMO today shows the UK lying in a unstable WNW flow at the end of the week and weekend between a Low pressure belt from Scandinavia to Iceland and High pressure between the Azores and Portugal. The basic alternation between mild and damp weather and colder showery conditions is shown to persist with the most emphasis on the colder, wintry shower type conditions held across Northern areas more than the South in quite fresh to strong winds at times.

THE FAX CHARTS The Fax Charts today show the current slack flow across the UK gradually becoming replaced by a stronger SW flow following a warm front NE later tomorrow. Trailing fronts then get strung out across Southern Britain later in the week with a cold and showery Westerly flow to the North which extends SE to all areas by Friday and next weekend.

GEM GEM shows a strong WNW flow across the UK next weekend with showers or rain at times, wintry in the North. Following a ridge of High pressure late in the weekend the run up to Christmas looks mild and rather cloudy with a little rain as High pressure to the South edges ever close to Southern England pushing rain bearing fronts more towards the far North and NW.

NAVGEM NAVGEMlooks quite similar to GEM in theme bringing mild SW winds on the Northern flank of High pressure over the near Continent. All areas would likely become quite mild and beign in the South while the North and NW see rain at times in the run up to Christmas..

ECM ECM this morning shows a mobile Westerly type pattern through the period gradually becoming less unstable and milder with time as High pressure over nearby Europe becomes more influential in pulling milder uppers across the UK ina SW airflow on the run up to Christmas. Christmas Day which is at the close of the run this morning shows an active cold front crossing the Uk from the NW with rain follwed by wintry showers across the North and West.

ECM ENSEMBLES The ECM Ensembles continue to illustrate a bias towards Low pressure being to the North of the UK and High to the South in 10 days time with the balance still well in favour of Westerly maritime winds driving rain and showers across the UK with brief colder interludes across the North in otherwise average temperature values.

NOTABLE TREND CHANGES FROM PREVIOUS RUNS Trends remain weak this morning with the trend for longer milder sectors across the UK towards Christmas perhaps being pushed away over the holiday itself by another shot of colder polar maritime conditions with showers, wintry in the North although this is by far a done deal as there are plenty of other options shown none of which translate to anything particularly cold within that time juncture.

MY THOUGHTS It's still like looking for a needle in a haystack in our quest for cold weather or at least a break from this well worn pattern of High to the South and Low to the North of the UK that has been persistent over the last few weeks. This week seems like the usual mix of wet and mild or cold and showery weather that has been the case for a while now where the North hogs most of the chance of any wintriness in the form of showers while the South stays milder and less wet but generally non-descript in weather terms. It then appears that after a brief shot of colder air at some point next weekend for us all things get worse as High pressure settles over nearby Europe steering mild SW winds across all of the UK in the run up to Christmas with leaden skies and rain at times no doubt. ECM then shows an active cold front moving SE Chrismas Day morning which could turn things more seasonal over Northern hills at Christmas along with frosts at night almost anywhere but this looks unlikely to last as many output members follow the well worn track of a ridge followed by a return to a relatively mild and Westerly pattern post Christmas. With the ECM Ensemble pack looking far from anything exciting this morning citing a continuing spell of Westerly winds between Low to the North and High to the South at Day 10 there has to be little optimism from me this morning that we are looking to any major change anytime soon. With it now being several days since rumblings of a change in pattern could be on the horizon from those best in the know we continue to see little evidence of this being translated to the models and it will be interesting as a result of this whether the Met Office revise their thoughts over the coming days to something that we don't want to here. My own feeling is that this looks like shaping up to be a very Azores High driven Winter and while it is always a pain in the backside even in our colder Winter scenarios of the past this year it looks particularly strong which is why I maintain our best shot of cold will be from a Northerly rather than Eastern quadrant with the caveat if at one or two times in the coming months the Azores High ridges to Greenland it may deliver us some real cold later in the season even if any particular spell will not last that long. Meanwhile we have to sit and wait and wait. One thing that looks very certain this morning is that away from hill of the North it is unlikely that there will be a widespread White Christmas across the UK this year.

Pretty much 0% chance of a cold spell when Dutch ensembles are this mild. 

http://www.knmi.nl/exp/pluim/vijftiendaagse/index.php

Remembering that our cold weather doesn't just come from the East

I think that patience will be the name of the game at the moment. It's worth remembering IMO that at this time in December two years ago, the model runs generally did not look inspiring at all for those wanting cold, and yet look at how much things changed that winter once the festive season had passed. As far as I know, it was a SSW that took place over Xmas 2012 & New Year 2013 that largely altered the course of that winter, and with stratospheric warming seemingly taking place at the moment, or about to take place as I understand it, then who knows.

One thing I would be extremely surprised about is if virtually every week of this winter turns out to be exactly the same for weather, as happened last year. That must have been a rare occurrence given how variable the UK's weather usually is.

Agree, but you'd want them to be a lot  colder than that even from a Northerly. These ensembles pretty much rule out any significant Easterly or North Easterly for the next 15 days. 

Its been like pulling teeth trying to get to this cold spell. Last year there was pretty much no hope for cold so model watching wasn't so bad. It's the hope that makes it worse this year. 

Thought I'd do this post while the going is quiet at my end.

All looking uninspiring in terms of proper winter-like weather over the next couple of weeks - unless you live in the Highlands.

Like for instance, this is the GFS output for this Friday, showing rain clearing with a brisk showery type westerly airflow flowing on behind - all pretty much nailed on at this point:



And how the far reaches of the ECM model is showing an uncannily similar output for Christmas Day . . .

It's like playing a game of Spot The Difference.

Of course, it doesn't tell the full story as I try and take into account the 850 hPas- but even the 0 C to -5 C zone at the 850 hpa level are remarkably similar on both outputs (-5 C over North Scotland to 0 C over North England - although the 0 C line is a little further south on the GFS version) so once again, it seems Scottish Hills continue to do well snow-wise while the rest of us will have to make do with typical winter fare.

Naturally, the ECM version is classed as being in FI land so it shouldn't really be taken as gospel anyway.

Still, it could be worse (eg, last Christmas and we all remember how awful that was - even though it actually turned out decent on the day itself) so we shouldn't really grumble too much.

Like I said, this is my own take on it as I continue to fine tune my own forecasting methods in the name of my own role as The Cloud Master so I'm sure I may be missing something but it does go to show how our climate is very good at "resetting to default mode".

Exactly Marcus, we have plenty of snow up here at the moment which has come from the NW

I don't look to the east as it is poor up here...i think people need to realise there is more to the UK than the SE.

In your location and altitude -5C uppers from the west / north west cut the mustard. In the rest of the UK they don't. Agree with your point about the UK and have made an effort on the site homepage in the last couple of years to reflect this. Nonetheless, it's a distinct possibility that by the end of this week CET will edge above the December average and this is more representative for the majority of the population.

95% of the UK hasn't seen any snow from this NW spell. 

I think people already know that there is more to the UK than the SE, but even away from the SE there aren't many who live at 900ft ASL
I thought we'd moved on from the frustrating IMBYism that existed in this forum for many years, but I might be wrong.

I agree Brian, we just seem to have an obsession with what is coming from the East, not all areas benefit from this - this is what i was pointing out.

That Euro/UK ridge depends so much on what takes place in the 5-7 day range, during which there is so much uncertainty upstream from the UK that I  wouldn't put much faith in any output beyond that period at least as far as the Atlantic pattern is concerned.

Take the day 5 ECM and UKMO charts for example:

ECM (left) has the low in the far-western N. Atlantic in the current consensus position, but UKMO shows that this is not yet nailed on, with the low further SW.

As this evolves further, we see GFS and GFSP driving the jet NE while ECM drives it more E, despite that low being in the same sort of position on day 5. This is due to large differences in how the U.S. pattern evolves on day 6:

GFSP (left) has a shallow low N. of Florida and a weak ridge to the north of that. ECM (right) has a much stronger low and ridge combination. The strong ridge on the ECM run keeps the Florida low on a path a bit further south than GFSP's solution, and more importantly, takes the momentum out of it, causing it to become slow moving west of the Azores with a ridge ahead of it for day 10 - a good way to draw the Euro High west again.

GFSP lets the low continue on east, locking the Euro High in place as it rides up the NW'rn flank. Only after it has passed can the upstream Pacific/U.S. amplification begin to show its hand (poorly shown on the 00z op run as that low from Florida parked NW of the UK - among the worst possible outcomes. No such issue on the 06z).

I'm going to focus on the 5-7 day range until these upstream issues are resolved, though I will an eye on the powerful East Pacific ridge and associated U.S. amplification from around day 9 or 10, as that's such an important piece of the puzzle for the turn of the year. For what it's worth, the super-strong UK Highs seen on some recent GFSP runs represent a 'slow burner' response that could just be a prolonged spell of increasingly cold anticyclonic conditions. It would be an interesting position to be in while waiting for the strat. driven impacts next month.

As a final comment, the difference in the arrangement of features in the Atlantic  between ECM and GFSP, while notable in terms of the UK outlook going forward, aren't actually that large as far as conditions in the next week is concerned - there is low uncertainty there, with the only likely variations being just how quickly the NW flow next weekend is cut off and then how soon milder air arrives from the SW (UKMO has the slowest outcome in both cases).

And furthermore. Here's real proof on how you just cannot take the very far end of the low res medium range output seriously, like one should never do.

Take this this 6z run for instance

This is by the old skool GFS at 384 hours, obviously getting out of the wrong side of the bed in the morning . . .



And the output by the posh new GFSP involving the same run time and at the same time frame . . .

Knowing our luck, it'll probably be the former that'll end up being verified come the moment.  

I see that GFS in the 6z is still running with the idea of rapid height rises over Greenland/NW Atlantic just after Christmas. This generates a lot of cold air to our NW and progressively to our West, and even our SW, as the run continues.

The strength of the Euroslug prevents the cold air reaching our shores on this run. However, it is interesting to note that even at the end of the run the High to our NW stays firm (1050 mb), driving the Atlantic lows further South than recently.

All FI of course but an interesting trend over recent GFS runs nonetheless, which could easily end up with a very different outcome. 

Here we go again  

Every sodding year on TWO we have to see this nonsense.

Comparing today's GEFS line plots for Plymouth and London with those of the 12z output yesterday, has revealed almost no change as far as the number of colder outcomes at 850hPa is concerned.

Being at the 850hPa level, surface conditions won't always reflect this due to low-level modifications (e.g. a -5*C northwesterly is a lot less cold at the surface than a -5*C easterly), but it offers a reasonable guide to how GEFS are trending (or not trending anywhere, in this case).

The method I use considers the number of runs hitting various temperature thresholds and also to what extent the mean does. Inspired by Retron's ensemble watch of years past.