Rob K

Even out to 240 ECM still holding the block and sending the jet underneath http://www.wetterzentrale.de/pics/Recm2401.gif I don't see a quick return to mildness from that run.

Not very similar those two charts. ECM maintains a block to the north sending energy southeast. Not a total undercut but not at all a GFS scenario. In any case I can't imagine that low being as ridiculously deep as modelled.

Ian there is a big difference between advising caution and just dismissing out of hand any cold charts while supporting any milder ones without question! I suspect your rationale is that if it turns mild you can claim the plaudits, while if it turns snowy nobody will care anyway. Possibly, but it does become a little tiresome and is not very objective! ECM 12Z, in any cold fan's book, is a great run, with classic synoptics. Look at Feb 1978 - you do not need massive heights over Greenland to get major snowfall: http://modeles.meteociel.fr/modeles/reana/1978/archives-1978-2-19-0-0.png

Erm, no - I'm not sure how you read that into my post! All I am saying is that the fax chart on its own doesn't add much to the discussion because we already know the Met Office is siding with its own output, blended with ECM, and discounting GFS. So the fax chart is as expected. The Met Office clearly think extended cold is on offer, and with ECM (det plus ENS), MOGREPS, UKMO, ECM seasonal forecast out to March etc etc all pointing that way then clearly that is the favoured solution. BUT.... we all know that if anything can possibly go wrong, it generally will.

Yes it did. The Fax chart is not the same as UKMO output - it is frequently modified to reflect forecaster's thoughts. It showed a decent easterly setting in at T120, then the next day the equivalent 96hr chart was redrawn with a UK high.

Yes, it would never show anything else because it is drawn to reflect the Met Office thoughts. By hand. It doesn't prove anything as we already know what their thoughts are!

I don't know why the discussion about the Fax - we know the fax will support the cold solution because it is drawn by the Met Office forecasters and they are going with the cold route (for now). But a word of warning - in December the "beast from the east" made it as far as the 120hr fax chart and was swiftly erased the next day.

Thing is there is no "reverting somewhat" - either the block goes up to Greenland and gets cut off and becomes stable for several days, or it sinks and is squashed flat in very short order. There is no halfway house here. It's a fork in the road - you can't go straight on.

Your analysis looks rather off beam, I have to say. Temperatures would not be nearly so mild, and precipitation would be almost exclusively snow from 96 hours onwards based on those charts. Perhaps you are applying a "fudge factor" because you believe the charts would downgrade, but that is not discussing the output at face value. For example, the 144 hour chart shows 500-1000mb thickness of about 515dam in southeast England, with 850mb temps of -9 to -10C. Anything falling in that would be snow and only snow. So to say "Rain and sleet showers on eastern coasts turning to hail and soft hail in land with some snow flurries over higher ground" is, with respect, very misleading. Not sure what you are trying to achieve with this?

Very interesting stuff Ian, thanks,. I've just watched your forecast from earlier on here http://news.bbc.co.uk/weather/hi/news/newsid_7760000/7760862.stm - very good clear explanation of what's happening (or might be happening!) Wish we had more of that rather than the dizzy blondes (of both sexes) moaning about it being bitterly cold if it drops below 8C...

Meteociel has the charts in 12hr steps but still doesn't show the magic -20C: http://modeles.meteo...56-2-1-12-2.png 11/12 Jan 1987 also got very very close: http://modeles.meteo...7-1-11-12-2.png http://modeles.meteo...87-1-12-0-2.png http://modeles.meteo...7-1-12-12-2.png So -19C has occurred more than once but maybe not quite -20C?

I'm pretty sure -20C has just clipped the UK on more than one occasion. I think I found a chart in the archives from some time in the 1950s when this question came up before? Will have a look... Edit: think I was thinking of Feb 1/2 1956. Neither of the charts show the -20C isotherm quite over the UK but I reckon it must have crossed over the SE coast in between the two charts: http://www.wetterzentrale.de/pics/archive/ra/1956/Rrea00219560201.gif http://www.wetterzentrale.de/pics/archive/ra/1956/Rrea00219560202.gif

The Met Office seem to have an allergy to the word "snow" in their text outlooks, I think because they are worried about causing panic. They almost always say "wintry" instead, either "wintry showers", or in frontal situations "rain turning wintry". Just one of those quirks... I remember one of the most notable things about the run up to Nov/Dec 2010 was that the Met updates actually included the word "snow" with no qualifiers. I commented on it at the time...

Yes that is what I was thinking. Often there is a halfway house but the GFS and ECM go off at such wildly difficult tracks that the only compromise would be a high sat over the UK with yet more gloom. So quite possible I suppose actually!

No evidence other than 10 years or so of looking at the models! And we know that to get a decent cold outbreak in the UK everything has to be "just so" to overcome the natural mildness of our location. Generally if one of the models spots something that's not quite right then the whole house of cards collapses in short order. I'm not saying that will necessarily happen, just that I think it is more likely that GFS will flip towards ECM than vice versa. Fingers crossed that I am wrong though!

Ian Brown is right that in general, if there is model disagreement, it is the milder solution that is the correct one, whether that is ECM, GFS, UKMO or whatever. You could say that at least 9 times out of 10 just because of the balance of probability. Any one missing ingredient and you end up with mild. That's just the reality of UK climate, much as I would love something like the GFS 06Z to occur!

Which day was the "epic" ECM easterly run from last week?

53.8N, 5.4E is just off the coast of the Friesian Islands in the North Sea... Surely not a hope. It's been lashing down with cold rain for ages and everywhere is soaking.

That chart is already cold. Dry your eyes.

120 hour fax chart http://www.meteociel.fr/ukmo/fax/fax120s.gif All good.

Exactly. Trying to pin down the 0c isotherm at 288 hours is just ridiculous. The general theme shown is for Atlantic lows to slide under a northern block. That means that a significant snow event becomes more likely, regardless of the specifics shown on each run.

Some very enticing solutions showing up in the long range recently. Factor in the GFS tendency to overblow Atlantic depressions and you could see an old fashioned blizzard from the sw quite easily. That would always introduce milder air in places of course but they are the source of the true classic dumps of snow.

North is good. It means pressure is lower over the UK and stops the block sinking. If the energy went over the top then it would be game over for cold fairly quickly.

I think that's the switch from low-res to high-res causing a jump. You sometimes see a "break" in the line there, it's just a problem with the chart drawing I think.

People that compalin about the "dry" flow... I remember with great clarity how people were moaning about the Jan 2010 NE flow being "bone dry". Then at 36 hours' notice this low cropped up and dumped several inches of snow across much of the south. http://www.wetterzen...00120100106.gif There was no hint of it even 2 days before - the models just showed a straight and slack flow. My point it, trying to pin down specifics more than a couple of days ahead is pointless. Look at the bigger picture.