Mucka

I think GFS has been sniffing glue again. Where's the bin? UKMO looking good but could do with getting the cold air further S for Xmas day

ECM is more inline with my prediction before the 00z this morning, in that low pressure disrupts into the continent and we find ourselves in E/NE flow only still a little further N than I ultimately expect. At the moment it is still far enough N to affect the UK and keep those pesky Southerners happy but if the other models come on board then it will likely continue to be corrected S and not affect the UK directly. All that assumes this ECM run is on the right track and there is not enough evidence yet to suggest that is the case. GFS 18z won't add anything really but tomorrows UKMO and GFS 00z runs may correct S, we will see.

I am 100% certain of one thing. We have not yet seen the correct solution modelled. Interesting to see them start to play with the idea of stalling the low now. Looking through GFS ensembles there are many options but the main ones either stall the low to our W, have the low disrupt further W and S through Iberia, disrupt it through the UK or have it blow up and barely disrupt through the UK (they are moving away from this) Low stalls Disrupts further W Disrupts through UK Blows up, little disruption. (I always thought this unlikely and glad to see the output perhaps moving away from this possibility) There are of course plenty of other variations to those main four but overall the 00z ensembles look good synoptically even if that is not properly reflected in the graphs with low 850hpa temps. My reasoned guess, but it is a guess at this stage, would be that low moves SE into the continent and barely affects the UK, probably not at all and we get a E/NE feed. Sue me! We still have a very good shot at seeing snow either/or Xmas eve/Xmas day/boxing day to lowland England and plenty of drama to come.

Yes GFS Op is definitely at the extreme end of milder runs over Xmas, an outsider at 20/1 in racing terms.

Here is how the Atlantic trough is modelled at just 96h GFS/UKMO As others have already said, the GFS is infamous for blowing up Atlantic lows and the Euros generally model this area much better in these timeframes. The GFS is good for picking shortwave energy around Greenland when we are worried about building heights into Greenland but that is not of concern here. It could go either way obviously but I still favour snow for some in England over Xmas eve/Xmas day and /or Boxing day. Place your bets.

GFS could be right but is probably wrong. We are now starting the countdown though as the set up happens within 144. This is a complex setup but because we are talking a few hundred miles whether snow or rain for England on a global scale and very small changes in timing and energy distribution makes huge differences for us. No better example than the 06z run and 12z run on GFS and there is no reason to trust one output over another as far as I can tell thus far. It really is knife edge and just for once I truly hope this goes right for us and at least some of us on low ground get a white Xmas, especially what we have all been through, but if not enjoy Xmas with family friends while you can. Fingers crossed for a better ECM as the countdown begins, I have a feeling the UKMO will come good tomorrow.

Discussing where the snowline etc is on a run is fine and good but The NIMBY posts in the MO thread rapidly become tiresome. Take it to moans and ramps or regionals please guys. We are on the cusp of a cold spell over Christmas with a possibility of snow of falling anywhere but before we know we have dozens more model runs so please be excited for the prospects for now. Plenty of time for us all to cry into our Xmas puds yet.

It is just raised heights ahead of the low which would be a channel low dragging in the cold on its N flank. In perfect world you would already have cold upper air over the UK but that is just a case of timing.

For the first time all 3 major models currently show a cold outbreak leading into Christmas.

Ho ho, ho merry Christmas GFS playing scrooge as usual

GFS 12z ensembles suddenly very keen to have our old enemy the Azores high play spoiler in FI. Not sure where that signal has come from but hopefully it will drop it just as quickly as it has picked it up.

Off to bed. Enjoy the ECM everyone.

If we can get a GFS Op like scenario to unfold out to 120 then cold could well come before Xmas Eve. That would be perfect - prep the ground for the big day On the other hand it could all go TU and seem like a distant dream.

Yup cold locked in. I actually think it could have come earlier if anything so let's hope GFS is close out to day 5/6

Well since Iberian heights are in the convo then let's take a look at GFS Low SW of UK. where does it go? Iberia but it only takes a little correction S to E or for the Scandi trough to dig a little further SW (as it should have) and they phase. That would open the flood gates from the Arctic. So this was very close to pre Xmas boom and I expect any similar evolution in the ensembles will show just that.

GFS certainly making a meal of things considering where we were at 144 The forcing is 100% from the trough to the W and 0% from the trough to the E. Well that's GFS. Hope ECM can get somewhere close 144 or be somewhere between GFS and UKMO to see how it evolves from there.

Icon isn't a serious contender, I don't even look at it. UKMO is okay TBH, could be better but not bad by any means. I think this mornings ECM will be better as well. Just a hunch. Still away to go but I have a good feeling about a cold spell over Xmas.

Finally It is on boys and girls.

It absolutely is, just playing. Could be sweet by xmas eve. Either way the improvement was in the more reliable timeframes so a definite plus.

UK cold shield still dialled up to 11 though.

That is not how they work. We do say the models struggle more with blocking situations but that is not because high lat blocking is unusual Winter, it is because blocking tests the physics of the models much more as they attempt to calculate where all that Atlantic energy goes as it meets the block and also there is less data over the Arctic so more fallibility in that sense

An improvement. A little more undercut and disruption to the W and slightly sharper Arctic troughing to the E. should trun out better and at least a seasonable Christmas day looks all but locked on now.

Yes one time the Euro view is more useful. Should be a little more disruption and undercut.

Comparing to Yesterday there is a little more forcing from the West but the Arctic high is stronger and sharpening the trough to the E This is why the models are struggling so much 6 of one, half a dozen of the other.

Operational runs have slowly drifted away from Greenland blocking and have us in a constant battle of mid lat blocking trying to get further N but being overrun by Westerlies before rebuilding. Ensembles are all over the place with plenty of better options but also some with milder Westerlies. It would be nice to have this evenings ECM reverse the trend of lacklustre operational runs and begin a new trend.