It's rarely one or the other IME. Even when I've read comments saying it has to be 'either ECM or GFS' a blended solution somehow manages to be the outcome. 

most of the GEFS are better than the op and control, but perhaps that's because they don't handle the shortwaves well

There is a problem with extreme HP.Its rather like a balloon being blown up.keep going and it bursts.Thus the most likely outcome is complete collapse of the GH. If you look at the February 47 charts which had a month of northern blocking the  HP centres alternating between Scandinavia and Greenland ,  HP pressure was generally in the 1024mb -1040mb range.

The short ensembles are as far as I dare to look. Considerable scatter for the 850hPa temps from the 16th.

Yes that's why I feel that a decent cold spell should generally start with blocking to the NE, as this can transfer Westwards, unless you get something freakish like Dec 1981, then the door is open for the Atlantic when the GH weakens or retreats.

Poor again down here on terms of snow %
 

Very good point, one of the best Scandy Highs I have ever seen was late January 1972 when a pressure of 1050mb was reached over Sweden with a perfect ridge to the north of Scotland allowing a bitter and snowy easterly across the UK.

It lasted 3 days before the high collapsed and the Atlantic rolled in and cold weather never did return.

Andy

The difference between some of the perturbations even at 144hrs is interesting:

We have to continue to expect wild variations from run to run; especially from GFS.

It'll be interesting over the next week to keep an eye on the verification stats (for 500hPa heights) http://www.emc.ncep.noaa.gov/gmb/STATS/html/new_acz6.html.

Currently the correlation (31 day rolling average) for day 6 is:

ECM 0.875

UKMO 0.855

GFS 0.855

GEFS6z update:

The most pointless chart you will ever see but this is just for fun: - Looks incredible looking at where the winds would originate from!!

BUt BACK TO reality - we have a couple days of cooler weather then back to wet and windy so it seems!??

Just seen the lunchtime weather outlook for next week. The summary started with the word "chilly". Frankly that's all I needed to know. The Met Office seem to be backtracking on the proposed "cold spell" faster than Lindsey Vonn on skies..

ECM 00z ensemble for London:

A couple push a warm sector across briefly late next Wednesday, then 3 runs out of the 50 go mild on Thursday.  Much more scatter from Sunday week.  The main cold cluster weakens progressively through the week of 18th.

Not sure if this chart has been posted before - cannot find it.  Obviously still a way off but that delivers some sleet and snow for the east/south-east.

That little Low Thursday could be quite snowy over much of the country - after that looks odds on mild and windy again to me.

The ECM 00z run has the following maxima for me:

Monday 7C

Tuesday 6C

Wednesday 5C

Thursday 3C

Friday 3C

Saturday 1C

Sunday 2C

Monday 3C

That's rather more than a 'mini cool snap'

Yes, certainly with elevation.

Certainly the default bet would be a return to wet and windy but ECM doesn't offer that as a good possibility for almost two weeks.

In passing, ECM shows extraordinary cyclogenesis off the eastern seaboard between T+144 and T+168:  over 50 mb in 24 hours!  I mention it both because it's unusual and because it then pumps up WAA over the mid-Atlantic and spawns our surface high.

http://www.meteociel.fr/modeles/ecmwf/runs/2016010900/ECH1-144.GIF?09-12

http://www.meteociel.fr/modeles/ecmwf/runs/2016010900/ECH1-168.GIF?09-12

No he doesn't; that's not what he said.

If you believe the GFS run then it's still several days later, after next weekend.  But that's a big 'if', especially with the current uncertainties about the evolution of the pattern.

 I would not believe the papers  . Just watched the Farmers Guardian online weather forecast and it says colder but not very cold and snow with elevation whilst lowland and southern areas receive cold rain which is worse than warm rain. I would just like a week or two of coldish clear, bright frosty weather.

Not sure I agree with elevation, evap cooling could be the order of the day, a long way out of course but one to watch for sure.

Certainly evaporative cooling could be a factor if the system is slow-moving and winds are very light.

I only mentioned elevation as a guarantee of 'snowy conditions' but you may well be right that it's not necessary - thickness and 850 values are very good.

I wonder if it will still be there in 6 hours from now?