Yeti

I like to check this thread for photos and snow depths and so far hardly anybody has posted either!Come on guys, take some pics; get that ruler out! :lol:

Hopefully - later today looks like it might be a bit more promising for Cambs. I'm going back there on Sunday so I'm hoping there's plenty lying around by then for the inter-college snowball fight! The ENE'ly later this week must be promising for Cambridge, but you will have a better idea of how we tend to do in such set ups as this will be my first winter there. On the other hand I do hope I'll be able to fly as planned on Sunday! At the moment it looks like there could be problems with snow at Bonn and Stansted :/ Anyway snowy wishes to all... from a very white little village in the Bavarian Alps

It's very good, better than the 0z. At 144 it's similar to the UKMO but the low is even further S: http://91.121.94.83/modeles/gem/run/gem-0-144.png I did comment on this a minute ago but it must have got lost in all the bickering!

GEM rolling out now to 96 and is very good so far - the US trough is stronger and reaches further E, the block in turn is based further E and the low, crucially, is further S than on the GEM 00z: http://91.121.94.83/modeles/gem/run/gem-0-96.png Now out to 108 and this is an excellent chart for the SE: http://91.121.94.83/modeles/gem/run/gem-0-108.png Almost a channel low there and with winds ranging from NNE to ENE showers would reach many parts of the UK.

The FAX charts still have everything about 100-200 miles further S though, so it will be interesting to see what they put out tonight. Even that much of a difference could have quite a noticeable impact. As we can see from the rainfall totals the 12z was a fairly dry run for the UK which is what may be worrying people; however this will almost certainly change as the models pick up on disturbances later on (FAX charts are good for this too!). http://www.wetterzentrale.de/pics/Rmgfs144sum.gif

I would say the UKMO is more like ice cream than a vintage steak - some people are saying the GFS would give better convection vs. the UKMO but in reality the opposite might be true because of the uppers. The GFS still brings the low further N than the UKMO so the air over England is sourced from the near continent (which is warmed somewhat by the low as it moves in and sinks SE). http://www.wetterzentrale.de/pics/Rtavn1442.png The UKMO on the other hand sources the air from the Arctic: The colder uppers would probably give more convection than the GFS would... although having said that the surface flow off the continent would still be very cold. The SE is extremely close to that milder air however. UKMO a much safer bet long term.

Last Christmas I don't remember it going back to normality on the 27th, in fact I believe people were still talking about missing data right into the New Year! Anyway I can't understand either why there seem to be so many disappointed people! The 6z is still an excellent run, and anyway, it will be wrong!

To be fair, "Brian on TWO" claims that there is missing data every Christmas (or at least every Christmas when the models are disappointing). It's an old favourite here on NW. I've always been suspect of this idea and have never seen any evidence of it myself. A more likely cause is the established fact that the 6z is the least reliable of all the GFS runs, and that's saying something. Each run has different data fed into it (the 6z will have more of other types of data I should imagine - can't remember the details right now but they are in the guides somewhere). The NOAA discussion later today should give us an idea of which model is most favoured - yesterday they favoured the GEM/ECM and slated the GFS; hopefully this will continue.

The 6z has the trough over the US weaker at 144 compared to the 00z and this demonstrates perfectly the effects this would have. Still a very good run (!) but as the trough is weaker over Baffin and slightly further SW, the block retrogresses W of Greenland with only weak ridging into Iceland: http://www.wetterzentrale.de/pics/Rtavn1441.png As a result, the Atlantic low is pushed under the block at an earlier stage and then moves slightly more NE - and whilst this keeps the UK in an easterly flow, the rest of Europe warms (notice the southerly flow over the Alps). This then filters over the South of the UK as the source of the easterly is not as cold here: http://www.wetterzentrale.de/pics/Rtavn1442.png Not really too much to worry about at all at this stage but it shows how important it is for that trough to develop as deeply and as far NE as possible to hold the block further E. However I do remember the NOAA discussion yesterday suggesting that the trough should be weaker than progged, though still further NE, so perhaps the 6z has some support in this respect. Ideally we want the low to track as far S as possible, even over the Alps as in yesterday's 12z ECM although today's other models are still outstanding. :unsure:

Not sure if they have been posted already but the ECM ensembles are very good: http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png Lots of support for the op - and with the NOAA report that Nick has quoted it looks like things may get very interesting indeed. EDIT: I see they have already been posted!

Oh stop moaning, it's like Christmas day all over again! Be patient and I'm sure things will turn out well enough. Think yourselves lucky, all I have is rain and it's not even cold rain at that! I'm waiting for it to clear away so I can go out for a joint

:lol: :lol: :lol:

Lol I can't really complain I suppose after the extreme (even deadly!) cold of the last spell. Tbh though the DPs are 1-2 virtually everywhere in the Midlands - OK it's odd but if the Met Office have put out warnings for Leicestershire then you must have at least a reasonable chance. Of course higher ground will be most favoured, so that includes most of the West Midlands which will probably end up being best off in this setup along with the hills. May it snow upon you all

How's it going Andy? I'm stuck here in Germany, sadly it's 4c and bucketing it down with rain from the same front! Not only that but the cold air is moving S by about 50 miles per day so it will be Thursday/Friday before it turns to snow here. Sooooooo gutted! Oh well. Going to the Alps on Saturday Anyway the real action should all begin in the next hour as things rapidly turn to heavy, drifting snow in the Midlands...

I'm not sure that's necessarily true - it just so happens that this time the cold is held back by the placement of the shortwave over Scandinavia: http://www.wetterzentrale.de/pics/Rtavn721.png Remember that just before Christmas sub-20 air was entrenched over here and even stretched into France. On occasion, exceptionally cold air can make it to Europe, and that still happens (although perhaps less often). However, the Arctic is warming so in theory the probability of cold air reaching Europe ought to decrease (although not year-on-year - some years the Arctic is warmer than others obviously). As for the "perfect" scenario for cold to reach the UK... that would have to be the Arctic high moving S like 1987: http://www.wetterzentrale.de/pics/archive/ra/1987/Rrea00119870112.gif http://www.wetterzentrale.de/pics/archive/ra/1987/Rrea00219870112.gif I can't imagine any other scenario could possibly advect such cold air over the UK.

Great models again this morning - however the trend has definitely moved away from the Siberian link up allowing the really cold, unstable air to reach the UK. Instead the block looks set to extend SEwards, sending the coldest upper air into central Europe while the UK sits in stagnant cold which, coupled with fallen snow, could create some very low minima: http://www.wetterzentrale.de/pics/Recm1201.gif This is a chart that caught my eye: http://www.wetterzentrale.de/pics/Rmgfs1444.gif I'm sure that would be record breaking cold for northern Germany and we can see why the De Bilt ensembles are forecast to crash! http://www.knmi.nl/exp/pluim/vijftiendaagse/Data/15DAAGSE_06260_NWT.png Then once again the block looks like it may retreat westwards, allowing Arctic lows to push S. This would likely bring more moist but perhaps slightly less cold air, away from the North. All in all, plenty of cause for excitement as this long cold spell returns to northern and central Europe (or is refreshed in the case of Scotland).

Interesting, thanks... The UKMO 6z is certainly a lot better than the 0z and is MUCH more similar to the ECM which is encouraging! I know people are beginning to complain about the endless chatter about the track of the low but that's simply because it's two days away and will mean the difference between perhaps a foot of snow and absolutely nothing for some places. Despite the medium term prospects looking excellent, I imagine most people on here would rather grab a foot of imminent snow than wait for the next pulse of cold air that may or may not have similar snow potential for them!

Btw for some reason I've just been reminded of this chart: http://www.wetterzentrale.de/pics/archive/ra/2009/Rrea00120090210.gif This was the only other time I remember such disagreement at close range - the ECM had the track of that low further N than actually occurred and the GFS turned out to be (almost) right in all its insistence. In fact the ECM ended up being by far the weakest model and I feel we may be making the error of relying on it too much at short range (it is not designed for this purpose). The GFS/UKMO may not be as wrong as most of us would like. Personally I'm dreading the GFS being right as the weather would be truly revolting here!

But the FAX is already a "compromise" between the ECM/GEM and UKMO/GFS? http://www.wetterzentrale.de/pics/Recm721.gif The ECM doesn't tilt the low and it is further S so even down here sees an easterly. However the FAX have a lot more tilt to them meaning mild air for all of Europe except Britain/Denmark northwards: http://www.meteociel.fr/ukmo/fax/fax72s.gif The UKMO raw output and the GFS have this even further N: http://www.wetterzentrale.de/pics/Rukm721.gif IMO the FAX is already a compromise if anything leaning more towards the UKMO raw output. (I can't understand why people say it is more like the ECM? They are quite different.)

HAHAHA this made me laugh. Don't think many people noticed the cheeky comment there! :lol:

Here comes that undercut: Much better blocking on this run with a very different outcome to that shown by the GFS.

Well the UKMO 96-144 charts are now out on WZ and indeed it is a huge upgrade. http://www.wetterzentrale.de/pics/Rukm1441.gif Although this looks a bit "boring" for the UK, the block is a lot stronger to our NW and is slightly further S allowing ridging S and E into Iceland. THat pesky trough finally leaves Scandi and the N Atlantic, with a low about to undercut and a monster cold pool plunging into central Europe on the eastern flank of the block... Absolutely stunning chart :blush:

I'm not at all convinced this is true. Normally it is the ECM that is the kick in the teeth and refuses to back down whilst the others follow and the GFS carries on its delusions. When the GFS is against the ECM, UKMO and GEM I would never, ever place money on it being true.

There is actually a 6z and 18z UKMO but we can only see it out to 48hrs (not sure if it actually runs any longer than this). Everything looks to be going the wrong way atm and I'm not at all sure the ECM is particularly well backed up by other models. IMO the UKMO has more in common with the GFS than the ECM. Not only is the low too far N in the short term, the jet is too far N in the long term for the cold pool angled over Scandi to advect SW. In the UKMO 144 chart the Atlantic vortex is poised to tilt and blast the cold air away. http://www.wetterzentrale.de/pics/Rukm1441.gif Let's hope the ECM sticks to its guns tonight or I have a feeling major, forum-wide doses of prozac will need to be administered. Currently it's the ECM and GEM vs. GFS and UKMO... EDIT: 12z UKMO might just have saved the day

Look at the snowfall chart in the bottom right too. Not often you see that much forecast from so many members!!