Either that's a rhetorical question or you've been round long enough to answer it yourself. It becomes tedious repeating the same thing again and again. For the last time, there isn't much difference between the ECM, UKMet, GFS, GFSP and even GEM. Statistically the ECM is best, but for most of us here with full access to the GEFS (either via TWO or one of the other sites you use) this is the best tool we have out to 16 days.

Really?! I'd pay £1000 for that run to come off, look what we tap into when that trough clears.

Isobars right back to that -28C isotherm. And nothing to stop them with the monster Greenland block in the way. 

I'm afraid I disagree there. I'd say it is the best model for cold tonight and follows on from this morning's operational. The best thing is there is no Azores High, pressure is increasingly High towards Greenland and the High to the SE is declining. The deep Low sinking down to the NW is there as a result of cold Northerlies rattling South over the Atlantic coming up against opposing mild air over the UK and nearby Europe. I think given another day or two the UK could become under a cold blast from the North. It looks like Iceland could be the place to be from the 27th.

This is a great chart massive GH would lead to mega cold with in 2 or 3 days. With the vortex in the state it's in and the probable SSW sometime in January I think it's a matter of when not if this winter. Hopefully anyway.

http://www.wetterzentrale.de/pics/Recm2401.html

What it goes to show is, despite a proper Greenland block, its not garneted to deliver cold/wintry weather to the UK.

100% agree with this. ECM is very good tonight 

Watch the metoffice forecasts tonight, they have access to the ECM right to 384hrs. Ah screw it, I'm going to tweet beg them to show us an image of a 268hr chart!

At least the ECM 12z has not followed the lead of the GFS 12z; that was my biggest concern an hour or so ago. Maybe the GFS run is a mildish outlier- we'll see.

I think that the game is probably up in the first cold shot 24-28 being anything "special"; or indeed perhaps anything at all.  There has been a mild-ward shift and the parallel the Op and the control have tended that way.  ( GFSP not shown on the graph below for London):

Interesting times nonetheless

But we have to be careful Martin a lot of confusion with its members this morning very early on with energy into Europe

http://old.ecmwf.int/samples/d/inspect/teasers/samplers/banner/mean_sea_level_pressure_and_temperature_at_850hpa!120!pop!od!enfo!enplot!2014121800!!/

Plenty to keep all factions engaged this evening I see.

There is a move away from a Boxing Day cold shot it seems but this may be a slow burner with the ECM offering a taste of Nirvana if it were to go beyond +240.

It's a ride that has only just left the station.

I think we have see quite a few of these scenarios in the past where the cold keeps getting pushed back, sometimes not arriving at all.  Just saying...caution required in Fantasy Island as there be mirages of cold therein.  That's the fun part, reading the charts from "first principles" and trying not to get suckered.  Bring it on!

Agree with both WI and Neil's posts.

Having reflected on the output and also allowed the dust to settle from the early evening disappointment of missing out on the 26-28th December cold shot we should all still be mindful that the background signal for increased heights over Greenland is still very much there.

The ECM 240hrs looks like leading on to an almost late December 1978 evolution and there are still enough suites from the GEFS pack in the -5c to -10c range to keep interest high.

Reliable looks like about 3 days 850 only tell one story the pressure patterns are all over the place

we have to wait to let things settle

We all know what came after late December 1978- the last January to have a sub-zero CET.

Hi PL.  My point was that the key runs had all shifted mild and that the few pertubations still flirting with the -5 isotherm are probably going to disappear over the next runs.  Its not impossible that the ens could flip back but I doubt it.

The ECM ens posted above are from the 0z run I believe?

Steve - I see more parallels with the following year, but hey its 35 years back so are analogues still relevant anyhow?

Based on similarities to the 00z, which the experts looked on favourably, ECM does appear to be most in tune with the background signals in terms of the broad scale pattern becoming increasingly favourable as we draw toward the New Year, with the blocking to our NW being sustained as the jet splits over the Eastern U.S.

Split jets are arguably GFS' greatest weakness (out of many), and let's face it, GFSP has also been insisting that all of the energy would try to go over the mid-Atlantic ridge, with very decent amplification and associated WAA in the 6-8 day range being the only thing allowing the mid-Atlantic ridge to persist as long as it was on runs up until the 00z of today.

Now how about that Iceland shortwave separating the ECM run from the far quicker results seen on the GEM run?

It arrives in Greenland as a very ill-defined feature on day 6, then drops south and starts to develop on day 7.

The fact that it heads due south rather than southeast is unfortunate but entirely plausible - the low interacts with the jet on the western flank of the mid-Atlantic ridge rather than hitching a ride on the jet running SE through the UK. Had the shortwave been maybe 200 miles east, it would have tracked SE and the cold air would have persisted for another day or two until a probable interruption from Atlantic low pressure moving across from the SW (more like the ECM runs of yesterday).

This evening sees a situation where variation between the models and also within the ensembles is extreme, making it impossible to fairly assess the likelihood of any given run even for the 4-5 day range.

Even so, some attempt can be made in terms of the broad pattern.

The way that ECM splits the energy of the U.S. trough days 7-8 (unfolding above-left, day 10 result above-right) is supported by GEM and in fact GFS.

The latter just makes a hash of the Greenland Block because a shallow disturbance crops up right in the middle of it on day 8, causing all of the higher heights to end up over Alaska by day 10. Even at that point, as mentioned earlier, it nearly recovered the situation as higher heights renewed their advance on Greenland from two sides at once... but it wasn't to be as the split Atlantic flow was suddenly ditched. The level of poor fortune is in keeping with the theme of the evening op runs.

I keep mentioning the split flow now because I remember Tamara talking a day or two ago about how the background drivers should be supporting that during the final week of the month (for those who know their mechanisms, we're talking falling atmospheric angular momentum and a favourable phase 1/2 to 3/4 and back to 1/2 progression of the global wave oscillations).

We could really do with the GFSP 18z latching on to that split flow so that we can get another higher-res opinion on the results down the line out to day 10.

Of course that all assumes that the split flow is the way forward... many, many more runs needed 

Theres the ecm mean t168 the big day running a little ahead tonight perhaps its just want to get it out of the way

Another great post from SC thanks.

ecm ensembles again look very good just need to have a good Op.

http://www.wetterzentrale.de/pics/Reem1922.html

http://www.wetterzentrale.de/pics/Reem2162.html

http://www.wetterzentrale.de/pics/Reem2402.html

You have to read the time stamp backwards. 2014-12-18 00:00 means 00z on the 18th of Dec. 2014.

That chart might not be cold precisely for the UK, but has that wonderful general appearance you normally see only on archive charts for epic winters.

Chance of a December 1978 type  evolution is about 1% 

And here at least is a crumb of comfort: the 12z ECM SLP mean for the 27th: