You have been implying that the Atlantic would win out and that this was supported by the Met Office forecast. I was merely pointing out that the reality is somewhat different.

Ian simply seems to always go with whatever model runs and whatever forecasts are going for a return to altantic zonality Peter, even at times such as at present when it is by no means certain that will be the case. Last February was a case in point; even when the MetO were sticking quite confidently to their "Beast from the East" prediction at the end of the month, Ian was keen to talk up those model runs that showed the atlantic winning out and made comments along the lines of "I expect the MetO to change their forecast tomorrow", etc.

De- Bilt ensembles. Very good agreement for a significant cool down from current levels. How cold and for how long is far from determined. Operational run was the coldest in the pack but not a detached outlier. 

For an easterly here its worth adding 2 or 3 degrees C to these values. 

http://www.weersite.net/?actueel&ensemble&ecmwfpluim

Lol, great reading tonight.  It was just the same leading up to the Beast from the East: the models were the same flip flopping ebb and flow that kept the stress levels at red alert status, fuses shorter than pencils.     

At at this time of year the jet should be at its strongest, so any sort of a block is unusual, welcome, interesting and hopeful. They are for the same reasons often short lived, with both initial wintry precip and transitory, sometimes repeated transitory as milder air nudges up from the south and collapses back down as the euro low recedes or fills. 

This range, it is trends only, but the beast build up was just the same as this...but it came, and when it did, for me, it was better than anticipated, my road had 4ft drifts blocking it, and -5 max temp, Awesome! 

Repeated blocks, even short ones - are a good sign of this pattern repeating...

Enjoy use ride....

The op really did drop into the freezer for De Bilt didn't it? 

GFS 18z has the main LP further west and, because it hasn't dropped the surge of Arctic air out of Canada, doesn't produce that major LP that zipped east and broke the block down.  As a result the block is further west and the WAA gets further north again.

Ian will be heartbroken....

T+192

GFS getting aboard the ECM train; let's see where it goes after T+192.

Lovely positioning to the Scandi but the upper are widely -4/-6 on this run.

But the 500-1,000 hPa thickness values are in the mid-520s: still a little high for wintryness to low ground perhaps.

Detail. Odds of a Scandy High next week up a couple of notches this evening.

Depth of cold and ppn type and distribution can not be defined yet but based on dps alone it’s going to ‘feel’ much colder at least.

You can sense that something is afoot when a deep LP exits the eastern seaboard and then tracks slowly north towards the SW tip of Greenland.  I would guess there's a decent chance of it promoting more WAA and pumping up a Greenland high, if the jet plays ball.

Even if there is a colder snap, nothing in the MO looks particularly favourable for sustained cold.

Nothing to be excited about at the moment.

I'd rather a stable high sat bang over us for a couple of weeks. Maybe 'faux cold', but some prolonged frost and fog would be the next best thing to snow sat on the ground in the festive build up.

GEM 12z showed snow into France and the low countries but most of the UK misses out. It's always an uphill struggle here unless we hit the bulls-eye, especially this early in the season.

https://www.theweatheroutlook.com/twodata/gem.aspx?run=12&charthour=240&chartname=nhprecipratec&chartregion=nh&charttag=Precip%20type

Mid AFTERNOON 13th December on Thursday it's -7@ 850hpa:

Maxes of +2 or 3c in south with sleet/snow showers moving in from the SE.

Meanwhile the strat becomes increasingly toasty on an increasing number of model runs

https://modeles.meteociel.fr/modeles/gfs/runs/2018120318/gfsnh-10-384.png?18

I maintain that the ingredients are coming together for a severe spell of weather after Christmas and into January

Just for fun:

It's still too far ahead to call the detail, but the lack of cold uppers is perhaps a product of winters today. Nevertheless, I'll take it over zonality. Whether we get snow or sleet may depend on the humidity. Hoping for drier air as this would deliver snow even at fringe thicknesses...

ECM 12z ensemble for London

The growing uncertainty that was revealed on the 00z has been replaced and we're back to a solid main cluster going with maxima of 2-3c before a split develops with a greater chance of a return to more normal temperatures.

The op was at the bottom of the colder cluster for days 6 & 7 but not an outlier, except for the minimum on 12th.

Whenever the block arises from a pulse of WAA we are wholly dependent on the airmass drawn south by the corresponding CAA on the eastern side.  The only way of avoiding that is when an Arctic high forms the block, and they're as rare as the proverbial hen's teeth.

Not sure what you mean by “lack of cold uppers”, they look pretty cold for a transient block in the first half of December!

A decent 18z suite for London!

Yes, I haven't got involved in this thread because we all know how this ends

The High ends up much further south and the cold goes to Greece

Morning. 

Better support this morning from the GEFS for the Scandinavian High and resultant easterly.

Uppers are too warm with many drawing in an easterly feed with 850Hpa temps of -5c to -7c. Enough to make it feel very cold, raw, dull, damp and sleety over high ground in the east but insufficient to bring an early white taste of winter.

GEFS mean at 168 supports a better propped HP compared with the 180 chart I posted last night.