I'm waiting for a Ferguson quote from NW talking about things being "bothersome" or "MOGREPS/progressive/ +<-EURO4/detailing/"

More runs needed. Easily the most accurate statement in these threads every winter 

Have a good one as well, Matty.

wasnt it Glosea5 that originally picked up a signal for new year/early January, which was quickly dropped after MetO favoured a westerly bias?

Yep, up and down, back and forth quicker than a self employed brass.

The 18z GFS run also results in the polar vortex being split apart and dislodged completely away from the Pole by the end of the run. If this were to verify it could make for a very interesting January. The GFS(P) does not show the same result so a large degree of caution needed as this is just one run. But it does show nicely the art of the possible.

Polar vortex as of today - some pressure starting to build on the vortex due to warming in Siberia
http://modeles.meteociel.fr/modeles/gfs/runs/2014122318/gfsnh-10-6.png?18

The warming over Siberia intensifies reaching a temperature of -12C by 29 Dec putting more pressure on the vortex which is starting to elongate
http://modeles.meteociel.fr/modeles/gfs/runs/2014122318/gfsnh-10-132.png?18

By NYE the vortex is highly elongated and is starting to migrate towards Scandinavia as the warming continues to exert pressure
http://modeles.meteociel.fr/modeles/gfs/runs/2014122318/gfsnh-10-192.png?18

By 6 Jan the vortex has shrunk considerably and although now somewhat circular again is way south of the Pole moving into Russia
http://modeles.meteociel.fr/modeles/gfs/runs/2014122318/gfsnh-10-324.png?18

By the end of the run we have a split vortex with a second cell over the US. A large area of elongated warmer air is aligned north / south across the Pole from the Canadian Maritimes across Greenland, the Pole and then down into Siberia. Instead of a typical west - east flow normally associated with the vortex at this time of year we have a north - south flow through that area of warmer air which increases the chances of cold air flowing out from the Pole into the middle latitudes.
http://modeles.meteociel.fr/modeles/gfs/runs/2014122318/gfsnh-10-384.png?18

This is an incredible run from GFS but is it a one-off or the start of a trend?

Wasn't expecting that run from GFS!....  After year's of model-watching experience, and the chopping and changing of recent days, I'm sceptical to put it mildly...  I feel I've more chance of meeting Santa himself this time tomorrow night than seeing this repeated on tomorrow's 4 GFS runs!... We'll see... 

EDIT: Apologies I made a boo-boo, there was an error in a script that had the date on the GFS image set wrong (I thought it was a little odd). Really sorry about that. Its fixed now! 

And both images agree and if anything the GFS has the more substantial warming, that being said this is merely a polar vortex displacement, rather than a complete deconstruction which is what we are really looking for.

Right click and select open in new tab to enjoy these images in high resolution.

Looking good at the weekend the furthe E/SE you are for some back edge snow and possible snow showers into the SE later. From an IMBY perspective nothing to write home about after the weekends rain some frosty weather and all in all bog standard winter fayre.

The strat. developments on the 18z are led through developments in the troposphere, namely a ridge nosing towards somewhere ranging from Greenland to Svalbard and battling the lows being spawned courtesy of the Canadian PV lobe.

For the ridge to do that, the undercutting Atlantic jet is needed as shown on day 8 of that run.

So it's all linked and shows just how much future potential can depend on whether the jet undercuts a blocking high or not.

I am wary of taking this run all that seriously given that GFS has basically behaved like a slingshot that was held back by a stubborn finger until suddenly being released, the new-found momentum then propelling it a fair way beyond anything we had been in the recent past.

GFSP has gone with some more cautious adjustments - the low this weekend dives south faster than the previous run but only so much as to bring it close to the ECM run, rather than leaping all the way over to the UKMO output as GFS has done.

We then see the Atlantic refusing to undercut the high, though admittedly the way the Atlantic behaves is so far from what ECM, UKMO, JMA and now GFS are showing that the blunt powering NE of the jet does seem highly suspect.

One thing that both GFS and GFSP do agree on is in fact the greatest gain of them all in my opinion - the low is now shown to slide without pushing Atlantic air towards at least the northern half of Scandinavia. That greatly improves the depth of cold air available from the easterly flow. GFS actually avoids bothering the cold pool with any Atlantic air at all, and then slides the low to Italy fast enough to scoop it west about as quickly as possible, so it was really a case of a lot of things happening to fall together just right - it would be truly remarkable to see a similar progression out to day 8 on tomorrow's 00z effort (let alone with GFSP in close agreement!).

Sigh... GFS went and did the only remotely possible thing that could have resulted in me starting at the model output until past midnight... models eh? 

GEFS Control plays the same tune as the rest of the models this evening. Keeps most of the UK in the freezer til Saturday ish..

...But most interesting is the lack of any LP to the north of the UK with most of the troughs being to the south of scotland.

need to see if this is an outlier

This brief synopsis covers days 4-6....two main camps today at this range, the GFS/ UKMO have gone with a short burst of NElies before sitting the high over the UK or sinking it.  A scan through the models and GEFS at t72 show considerable divergence of modelling on the track of the low, which then has big ramifications further down the line as you can see: All other models go for some sort of Scandinavian High, with some bitter cold.

All charts shown below are for t144, issued at 0000 today.

ECM will be of interest. At the moment its too close to call.

Enjoy your model watching today!   WI

UKMO

GFS: NB The control has more of a Scandi, the GFS P has one at 180 with snow flurries E and S

GEM

NAVGEM - at 180 is very tasty...this is 144

GME:(German?)

Only got access to the GFS 0z operational but it is very interesting. As seems to be the theme now, the low on Saturday is less aggressive but still a notable feature and it deepens as it sinks into the near continent. The faster advection westward of cold air on its northern flank will have the effect of creating a risk both in terms of back edge snow and snow showers following.

High Pressure follows in towards New Year and brings a spell of sharp frosts for many.

Thereafter we see HP to the east, eventually inflating over Scandi whilst low pressure swamps the UK.

All somewhat reminiscent of January 1984

It's wonderful today to see that the GFS suite has finally caught up with the cold spell - as shown as being the most likely option on the ECM ensembles for well over a week now! The switch between the 12z and 18z suites must surely go down as one of the biggest flip-flops in model-watching history. It also shows how a median high of 9C just 96 hours out can become a median high of 4C 12 hours later!

It also reinforces the GIGO* principle, that is that if the model as a whole is getting the pattern wrong then everything thereafter is pretty much useless.

Down here at least that's the coldest GEFS suite for a couple of years, with the typical cold spell look to it. It may not exactly be a snowfest but at least it'll be seasonal for once. Who knows, we may even get to see frost lingering all day in the shade, or even frost-on-frost!

EDIT: And for the first time in ages, the GFS anomaly charts show a sea of blue over western Europe.

http://wxmaps.org/pix/temp4.png

* An Americanism, for "Garbage In, Garbage Out"

morning all. Looking good for the ski centres in the alps and some frosty weather on the cards for us. Back off to bed, waaaayyyy too much beer last night. 

An almighty GFS flip-flop!

The ECM ens have pointed towards a cold spell for a week now (with some milder wobbles) but would you not say that even these have flipped? I think this because ECM was very keen on the Greenland block initially and has now changed to a block to the East or over the UK. It appears to have flipped from a cold outcome to a cold outcome!

TBH, when EPS first picked up on the cold spell there was very little info on synoptics, as we can only infer those with any great reliability 10 days out. Beyond that we have to rely on vague mean charts (which, as I often mention, aren't as useful as they're made out to be!). There's also the EPS control run, but that's not necessisarily that reliable either.

By the time the cold spell got within the 10-day frame there were two sub-clusters, one of high pressure over the UK and/or to the east and the other of northern -driven cold. Over time the cold clusters have gradually firmed up on the high pressure/eastern cold option.

The least likely option throughout was the sort of pseudo-zonal mush that GFS was churning out. As the GEFS ensembles are derived from the same code that runs GFS, it's no surprise that they clung onto a milder picture right until the bitter end.

Here are the 0z ECM ensembles with last night's 12z for comparison - again, a cold outlook, albeit with a good deal of scatter by day 10.

A wide range of options from the 00zs today with each model placing the high in different positions. The extremes are; the GFSP which builds the High more to our NE leading to a Scandi High and some cold uppers across the UK and the UKMO which sinks the High SE allowing milder Atlantic weather into the NW and anticyclonic conditions further South. 

Common sense suggests we'll end up somewhere in the middle but I can see there being a lot of to'ing and fro'ing from the models over the next few days before the final position of the High is nailed.

Based on trends, background signals, and a gut instinct it appears to me that we are about to embark on a very cold easterly, especially in the south with the chance of snow. 

Easterlies are the best source for cold weather IMBY lets hope you are right Steve, certainly more interest this year , for sure