I do have the postage stamps 120 - very interesting

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2016011312!!/

quite a few would lead to this... on a knifedge...

Met backing the cold to stay so hopefully the ukmo model is on to something.

Ian Fergusson Twitter 

W COUNTRY By weekend we see the coldest spell nationwide since March 2013: Atlantic mobility & mildness "not expected anytime soon" say UKMO

Yes, the switch from the op being in the coldest 5% of runs on day 5 to the mildest 10% on day 6 adds to the impression that the run is suspect between 120 and 144.

Next.

Encouraging words from Mr Fergusson.

IMO, it is the MetO's own model that has performed the most consistently of any in the past week, even though it only goes out to T+144. GFS in my estimation has had a nightmare of a time and I think it's sometimes too progressive nature has been exposed fully in recent days.

Agreed. It's skewed somewhat seen as it updates 4x a day, but even so it has consistently over-egged the Atlantic progression and then backtracked to the less-progressive solution  

Well said David.  The logical conclusion,If the UKMO is correct, is for trough development to the S of the UK and HP development to the N.  this would lead to easterlies.  We shall see what tomorrow morning brings.  I'm not bothering with the pub run.

That could well be correct two more fascinating quotes from Ian Fergusson on Twitter.

.whilst the parallel UKMO-GM starts mobility again next week *but* (unlike recent GFS), only across latitudes S of the UK.

subtropical storm Alex important in broadscale mix: huge amounts of warm air advection into W Atlantic to bolster blocking.

Is there a chance of deeper LP system forming over Ireland within the next few hours?.
https://max.nwstatic.co.uk/fax/20160113.1853.PPVA89.png.

Front edging down on the latest 120 Fax

Pinched this from the other side; the beginnings of Subtropical Storm Alex, whose forecast path can only be good for our block 

The cold really is hanging on

Mobility to the south of the UK.... Isn't that the holy grail of winter weather giving 1947-type Synoptics?

It certainly could be, as long as it's close enough,  but not too close 

ECM 12z ensemble for London:

http://www.weathercast.co.uk/services/ensemble-forecast.html

Solid agreeement between the GFS and ECM 12z runs out to the middle of next week and very little ensemble scatter in the ECM run either. Some support for slightly less cold conditions on Friday 22nd.  Quite a few members extend the cold past that weekend but there's only one smallish cluster offering maxima around 5C.

I've put the precitation chart in this post as well as it very dry after tonight's rain (London) and a brief and small amount of, I assume, sleet/snow on Friday afternoon.

Worth remembering that the ensembles are only testing for the stability or otherwise of the starting position - they can flip and flop just like an operational as/when new factors come into play.

That's invariably the challenge - low pressure typically brings warmer, moist air to bring the chance of snow but that opportunity can become a risk as well.    Deep and vigorous Channel Lows are the only way (other than low pressure from the east, which is rare) to introduce moisture whilst keeping the UK in the Arctic air mass.  But that puts, say, the south coast and Channel Islands at risk, of course.

1947 might sound like fun but, like another 1962/63, I suspect the novelty would wear thin after a few weeks when the disruption ceased to be a source of entertainment (for some).....

The GEFS remains mild this morning, with the majority of members going mild by 144 - only 4 members stay cold to 180. That's just as remarkable a turnaround as yesterday's 12z was compared with the 6z.

The GFS would give a snowy breakdown in favoured areas whilst the UKMO would be dry and cold before the high topples. Let's see what ECM says but neither run is exciting tbh. The UKMO has changed where it sends the energy out of Greenland suggesting less chance of the undercut

still such large differences at t+96 both between models and inter model runs it's hard to take any of them too seriously!

I think the chances of a major 'flip' are now beginning to reduce. Never say never (of course) but IMO I think the HP will eventually slip ESE and open up a NW/SE split across the UK. Milder air then looks like spilling into Scandi too. Who knows what will happen thereafter but my own gut feeling is perhaps a short period of a N-S split with higher heights to the S whilst the jet runs to the N and into Scandi.