Rob K

Nice chart comparison there. Sadly for some people here it seems if it's not Jan 1987 from now until next March it's a disappointment.

Ha, until GFS goes bonkers http://www.wetterzentrale.de/pics/Rtavn2281.png I somehow don't think this run will verify!

Not true, the 0C isotherm is at least 30 miles further west on this run! Seriously, all looks on track still. It's coming, 6 hours at a time.

I do wish people would stop mentioning 1991. We're not looking at that sort of easterly. At all.

Certainly more signs of milder stuff after midmonth than on the last run, but I suspect it would only be fairly temporary, The Aberdeen ensemble shows the cold air is not far to the north: http://www.wetterzentrale.de/pics/MT8_Aberdeen_ens.png My feeling is still erring to an attack (possibly snowy) from the SW, a brief warm up and then retrogession to Greenland and the possibility of some properly cold air coming down from the NE rather than the modest cold from the east that we are likely to see next week.

It's a balancing act though. If the block is too strong then you end up with most of the UK under 1030mb+ and very little precipitation around. With the LP to the south and a feed from the SE then as long as you can keep the uppers below about -2C then you can get some monster snowfall.

Yes Steve. I am not bothered about the fine detail for next week of the exact shape of the Scandi high and "Will it snow in Snivelling-on-Sea?" etc, but looking at the longer trend of the last three GFS runs in FI they have followed a very similar theme to our NE. I smell a trend and that trend says "Greenland High for Christmas". It's looking a bit 2010-ish.

Based on GFS FI trends over the past couple of runs I could actually see a Dec 2010 style event later in the month with a big Greenland High and the PV dropping down over us. Given that hadn't happened in 55 years before 2010, to have it occur again after two years would be pretty rare, but the general pattern certainly makes it possible. In he meantime, ECM on the face of it may look like a downgrade but those charts would bury much of the country in snow.

It is very much the coldest of any output though (e.g. GFS here http://www.wetterzentrale.de/pics/Rtavn2162.png ) and even then it's not a patch on the sheer size and depth of the 1987, or the intensity of the 1991 cold pool: http://www.wetterzentrale.de/pics/archive/ra/1991/Rrea00219910207.gif But 2009 would be plenty good enough for me - we got a good 15cm of snow round here with twice that on the Downs.

Yes it would get colder. But to see people asking whether it could be as cold as 1987 or 1991 is just asking for disappointment. No there is nothing on any model that suggests anything remotely as severe as those legendary spells. Something more akin to early Feb 2009 is a better match: http://www.wetterzentrale.de/pics/archive/ra/2009/Rrea00120090202.gif which led to http://en.wikipedia.org/wiki/February_2009_Great_Britain_and_Ireland_snowfall And even there the 850s were generally colder than I expect next week. I think a few people are getting unrealistic - yes we've got an easterly on the horizon but not a mega cold one.

Jan 87 was very extreme though because not only did the synoptics fall into place but they also did so at exactly the right time when there was a deep cold pool over the continent: http://www.wetterzen...00219870112.gif Even if next week's easterly is the most perfectly aligned, the cold pool is likely to be a good 10C warmer than that, even if you go by the more "extreme" ECM charts: http://www.wetterzentrale.de/pics/Recm2162.gif , so I hope nobody is expecting anything to compare with that one. No subzero maxes likely on this one, more like +2C with a nagging breeze. GFS shows the 850s even less cold, more like -8C.

If that is a 1991 forecast (I'm on my mobile so can't watch it now) then no chance. That was a once in a lifetime easterly. Next week I'd expect highs of +2c by the end of the week and a few snow showers with modest accumulations in favoured spots. I certainly wouldn't expect snowy Armageddon! Put it this way - I can't see anything as severe and snowy as Dec 2010 (or Jan 2010 when I got 25cm+ of snow here in Hampshire).

Very solid agreement of a 3-day easterly from the 11th to 14th at least. Although what are the chances that one solitary outlier has nailed it?

I actually think the final stages of the run in FI are quite encouraging, despite the fine detail. The PV relocating to Siberia is what needs to happen to keep the cold going. Otherwise the cold pool just runs out from the east and we get a gradual grey mushy warm-up.

That'll be Mr P. Vortex who has decided to visit Russia for Christmas, paving the way for a Greenland high to build and a shedload of cold air to come down to Britain from the north... http://www.wetterzentrale.de/pics/Rtavn3842.png (ignore the Dec 21 Mayan Apocalypse LP there and look at the general theme...)

Indeed not on that chart but I seem to recall back in December 2010 we were effectively under a chunk of the PV which dropped down through the North Sea... http://www.wetterzen...00120101216.gif http://www.wetterzen...00120101217.gif http://www.wetterzen...00120101218.gif The 06Z GFS control run actually did something rather similar in deep FI.

With the UK being where it is, there are always potential spoilers! However I would risk saying that the pattern looks pretty well locked in to bring an easterly for at least a few days, but that could be a weak and modified northeaster, a southeasterly, a slack easterly flow or a full-blooded beast from the east, depending on the exact position and shape of the block.

A question about the PV: I thought the signals were meant to be that it was going to head to the Siberian side of the pole, so why have the models over the past 24 hours seemingly ramped it up over NW Canada?

Yes, consistent in that the easterly is still at 240 hours, just as it was 240 hours ago ;-)

GFS 00z ensembles certainly suggest a big shift away from a cold solution for the UK with the block too far east. Still at least the block looks like forming which is a good first step.

http://www.wetterzentrale.de/pics/MT8_London_ens.png So the "dreadful" 18z was actually one of the coldest options?

Or perhaps not. GFS officially loses it there.

South westerlies? Where? Slider all the way there.

Greenland High about to come into play I think. Nowhere for the Atlantic to go.

Did I mention southerlies? http://www.wetterzentrale.de/pics/Rtavn2161.png I'd still back the cold air as there is nowhere for that low to go but underneath...