Really interesting that only 2 days here this month have had surface pressure <1010mb (both1009) and many are considerably higher. The only way I can justify this comment in terms of the thread is to say Wow! I wonder what that looked like on the model outputs- sorry. But it is remarkable that a winter month has had consistently high(er) pressure and has been a record breaker in terms of temperature. Sub 1000 in December is common. HP and cold combined is more common than this.

GFS12p is amusing

A slack flow causes the uppers to become very cold, if that thing ever gets to us....

November and December are the months with the highest mean precipitation (~60mm each), and this year they got almost zero. So it's completely abnormal. But to tell the truth, the 10 months before November were very rainy and we had already reached the mean annual precipitation by October. October had 2-3 times above average rain...

Now as for the snow, I hope this lake-effect part won't come true. Northern and eastern Greece cannot have snow at the same time. Northern Greece needs a low a few hundred kms south of it (which is usually created by super-cold in southern Italy) while Eastern Greece needs super-cold coming directly towards it for lake-effect snow(in other cases T is not low enough for sea-level snow there).

And since now we're going to have this lake-effect snow, there'll be dry weather up here... Maybe just a few snow before the super-cold arrives. Now, imagine how harsh it is to have sunny cold weather, and a 300kms south of you they get half a meter of snow. Nightmare.

PS. I don't know how you call the huge super-cold, low pressure area which is moved by a High in English (area with U shape and green color in Wetterzentrale) . I know that the mild, high pressure area is called ridge, but how do you name the first?

PS2. 18Z has just given heavy snow here on new years eve. Thanks Atlantic

Oh do show us the corresponding 850s; such fun.

I've not bothered looking at the output today until the 18z. Things should be back to normal tomorrow.

what do you mean by that? I thought the consensus was that missing data was a myth. 

That shows > 1065mb in Central/ Western Russia; surely that must pack a punch- can a high as intense as suggested not upset the fait accompli?

Does anyone believe that a low is going to be spawned in the middle of Europe out of nowhere like that? 

Bin the 12Z and the 18Z

I guess -15, -20 going into Baltic is pretty much a reason for a low to be spawned. If you mean that low anyway...

No- disregard the embroidery; look at the bigger picture- the persistent modelling of the rise in pressure that is signalled around the start of the year. I have learned from all of your discussions and the modelling that it's hard to pinpoint the shape & orientation of such a cell in advance and also that subtle alterations in its alignment can have significant impacts on weather at a variety of scales.

These signals seem to be highly variable on a daily basis.

Whilst sympathising absolutely with those whose houses/businesses have been flooded, if we weren't to get a shockingly cold spell, I'd be fascinated to see just how catastrophic this flooding could get.

18Z GEFS has 4 full on sub -10 easterlies and over half a dozen very close.

The guessing game continues into another day. For what it's worth I don't subscribe to the lack of data theory.

We're still a country mile away from sniffing an easterly- going by experience these things pop up  a few times within a 5 day period before fizzling out as we enter T-128hrs. 

I hope not, but wouldn't bet against it.

Missing data is a fact, the only question is how much of an effect it has on the models. Regardless of the magnitude of the effect of the lack of data, look at it another way - losing half the upper air obs for a day or two over North America, the Atlantic and Europe won't be having any positive effect, will it?

Here's the data input counts into ECM from aeroplanes - other sources, such as SYNOP/METAR, saw only a small (single-percentage) drop.

2212 155871
2218 228276
2300 208364
2306 153717
2312 161488
2318 230767
2400 206951
2406 159840
2412 137633
2418 189405
2500 160627
2506  80474
2512  74697
2518 173246
2600 159092
2606  84173
2612 123362
2618 196680

Coldest GEFS of the year so far - 5/21 runs show sub -10C 850s down here, which is the point at which I start to get interested!

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

This is how the cold spells of relatively recent years have first appeared, the odd straggler, then a cluster, then a majority cluster. It remains to be seen whether the same happens this time though!

The other factor is that there have to be supporting factors in place and this time at least the vast majority of the runs build that high to the NE - the uncertainty is whether it'll affect us, rather than if it'll form at all! As such, this is a long way off from previous "stab in the dark / random cold" outliers we've had this December.

I'm waiting for the meto to start to hint at this.

So far nothing, probably because the support is not great enough but the encouragement remains and there are a few potentially severe runs in the pack.

Fww, the GFS 0z operational is a shocker if you want dry conditions.

Yup, that's the case - going by ECM, for example, it's around 12% of the runs which bring a cold blast from the east, compared with (this morning, anyway) 24% of GEFS runs.

That tallies with Ian Ferguson's comments yesterday that the MetO were giving a cold spell a 10% chance of coming off. The threshold for it to be mentioned as an option in forecasts is presumably a fair bit higher. 20%, 33%? I don't know.

on this run on day 9 the ECM makes it, just...but fore how long?

This is getting EVEN MORE interesting...though the action is in FI, and we all know about that..........

and if I'm not mistaken, that is a snowy chart in deep FI on day 10, with cold uppers in the N and E and a frigid surface flow.  Will be interesting to see where the charts go over the next few days.  The first stage of the process - the WAA to the pole, is now well within the reliable though.

Yes Darren, a closer eye than usual will need to be kept upon the Met O textcast.  By tomorrow's 12zs we should be closer to the answer.

Edit - here's the WAA image :

t96 ECM:

Yes indeed a fantastic end to the ECM run with possible snowfest by day 10

http://www.wetterzentrale.de/pics/Recm1922.html

http://www.wetterzentrale.de/pics/Recm2162.html

http://www.wetterzentrale.de/pics/Recm2402.html

The GEM also looking snowy by day 9 good output this morning.

http://www.wetterzentrale.de/pics/Rgem2162.html