Eye candy, but unfortunately doesn't look sustainable, with low pressure to the west & east of Svalbard due to the northerly arm of the jet still existing.

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-0-384.png?12

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-384.png?12

Stays cold right to the end though with a decent battle , as you say eye candy and deepest snow   FI and be gone in an hour

I don't want to labour this, so I hope people won't mind.

Anyway I think we are seeing a downgrade in the general extension of the HP over the arctic and canada, WAA is not as extensive as it was before over N canada and alaska, and this ends up having a knock on effect on the UK. In the 8 days since this high started to become a major feature on the models, little has changed except: heights have become more prominent over N alaska, and things have tended to move more towards N canada than greenland. Wierdly we seem to be seeing a reversal now, to what the models were thinking a good few days ago, more communication with greenland but less WAA in general. As I am still more interested in this overall pattern than what is going on at the surface, my feelings are decidely mixed. A movement towards greenland is a much quicker and natural route to northern blocking, but I really don't want cold air getting pumped down the eastern seaboard either. And I can't simply call this an anomoly either since this sort of thing was first suggested by the ECM12Z yesterday and now 24 hours of model time has elapsed. Part of what made the cold spell so certain in my eyes, was the warm air and low activity over canada. If the models are trying to destroy this, then this also means a more northerly jet and the potential for large spoiler lows that could even end the cold spell entirely. So I am getting very nervous about the developments today, having said that the 12z ECM wasn't as bad as the GFS, and as happens so often the leader seems to back off. I would be tempted to go somewhere between the two scenarious (N canada blocking into W greenland vs more direct greenland blockig), which would perhaps lead to 5 days of sustained cold weather with a trough appearing sometime in the middle of that possibly causing snowfall on its leading edge. Beyond that the HP begins to breakdown, which would mean a reboot is less likely than a reversion to zonality. Also retrogression to Europe is far less likely with the 'pure' greenland setup than with the one involving canada. 

http://modeles.meteociel.fr/modeles/gfs/runs/2013112818/gfsnh-0-168.png?18

The cold looks to be a glancing blow to the North

NEXT....

Don't worry Marcus, it'll snow for 3 weeks once I go away...guaranteed.

http://modeles.meteociel.fr/modeles/gfs/runs/2013112818/gfsnh-0-252.png?18

And another glancing blow with HP left over the UK

http://modeles.meteociel.fr/modeles/gfs/runs/2013112818/gfsnh-0-324.png?18

I barely get any time to look at the models these days, and when I do it seems like half the time the output is nothing like what it was the previous day.

GFS suddenly has the strong and pacy Atlantic storm that ECM was showing until today, but has somehow managed to be even more progressive with it... or at least with the energy on the 18z run (12z had the whole system hurtling towards us at break-neck speed).

Based on recent times, I'd back the ECM 12z op run as of tonight, as I feel that we ought to be seeing numerous, increasingly gradual topplers over the next few weeks, with the extent of cold air involved becoming greater each time.

I must admit that for a time this morning I seriously considered the prospects of a snowy end to my university semester 

Another one bites the dust. So it would seem again. Perhaps it would be better if we could only see out to +144, then we wouldnt let ourselves get sucked in

I personally don't agree, with weaker blocking in general on these runs, this is to be expected. However there really has been little change in the grand scheme of things at all, so I still think a cold spell looks very likely. 

Seriously?

I cant see it. Our northerly is rapidly turning into a flacid north westerly, followed by a sinking high and then its goodnight vienna for the next 2 weeks

We say that every year

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-174.png?18

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-180.png?18

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-264.png?18

http://modeles.meteociel.fr/modeles/gens/run/gensnh-0-1-312.png?18

Control is a bit different

No, I said I would throw in the towel if something more direct didn't appear on the models soon. Remember I had put the latest date originally at the 7th of December, so if something more direct hadn't come up soon, then I would have been proven wrong. Luckily for me, about a day after I said that, stuff started to appear at the 192-240 range which is typical of when things do start to appear. Back when I said all this stuff about a cold spell a week ago, you all thought I was crazy . I probably am slightly crazy to be fair otherwise I wouldn't tell the time by model runs. 

An exponential improvement from 0% still leaves you at 0% doesn't it?

People take the charts way too literally imo. This is why my oppinions on here are often seen as so controversial, whenever I get excited by say a 168 chart that shows snowmagedon; its worth checking the wider context as things can fall down so easily. But of course it also works the other way. The major issue here, is not that mid atlantic high; it goes where it is pushed. The energy that is coming from the western part of the atlantic is the issue. And what we have is a weakened part of the PV with enough energy to send a spoiler low over the block. But personally I think this is wildly overestimated, though of course I will continue to revise my oppinion based on the charts. 

Keep the faith Q, the ECM ensemble runs are.....

Still no real shift - if anything the 12z is a degree or so colder than the 00z.

The Op was something of a cold frosty outlier from Day 8 - but almost a mild outlier on Day 7.

GFS 18z ensemble for London shows the Op still bouncing all over the place.

Indeed

The panel maps here show the problem, we have a sneaky trough that prevents the midatlantic and canadian high from merging which moves east towards the UK. The models then really struggle with what to do with it; merge it with the scandi low? Send it south towards Europe? Deepen it and send it NE and screw everything up? Well I would say this, its a shortwave feature, the details will change hugely before we get to that event, the longwave pattern will still broadly be the same. Basically any pertubation away from what we have now will probably be an improvement, and it seems odd that a low with such a southern origin should develop into such a deep depression. But obviously there is a probability that this will happen, I just think that the options of what happens to this low are much more wide ranging than the OPs are showing. So this is why it isn't that much of an issue to me, what really is bothering me, is what was shown on the ECMWF12z; a significantly weaker block. 

Totally differnet FI from yesterday 

This morning showing long feteched SW,After a brief 36-48hr Northerly

C.S

Another day, another round of "Spot the Outlier"!

http://www.meteociel.com/cartes_obs/gens_display.php?ext=1&x=306&y=141&ville=Londres
http://www.meteociel.com/cartes_obs/gens_display.php?x=306&y=141&run=0&ville=Londres&runpara=0&type=3&ext=1

Edit: And as it's not been discussed here as far as I can tell, yesterday's 32-day ECM control run shows a toppler at 240, another toppler at 360 and that's then followed by a relatively mobile period. Pressure eventually builds to the NE by 576. A battle then ensues, with a really deep low to the SW by 624 and strong easterlies over the UK (850s are only below -5C from northern England northwards, however). Christmas Day sees a trough moving NE'wards with heavy rain for all and the run ends (at 762) with a ridge over England and Wales and SW'lies elsewhere from a deep and complex area of low pressure near Iceland.

As will the 6z , 12z and 18z , that isn't a surprise