Ian Brown

Well I can't add to the hyberbole following the ECM, absolutely incredible synoptics. Going back to the old thread, somebody pointed out that there were runs on 27/1/12 showing -20HPA over Belgium for 5/2, I'm pretty sure that was only 1 ECM and perhaps 2 GFS runs. Even so, we need consistency of the pattern tomorrow even if we don't see such stellar synoptics. The NOGAPS supports the rather bizarre UKMO tonight it should be noted.

Excellent height extension towards Iceland - ' On the 12th day of winter the ECM gave to me, a massive Northern block and a biting easterleee'

Yes it looks a little bizarre as if the Atlantic is trying to keep it's foot in the door ! FI is different from the GFS but that is not surprise post High Res, the key timeframes are T120-T144.

Better than the 06z at the same stage, nice trough over Germany, should show a strengthening flow as the core of heights edges North.

The area around Iceland is crucial to geting that North and Westward extension, we want to see the 552 line up there on the models. Agree with regard to the 850hpa temps, I think these synoptics would have been a waste in mid-late November, but now with Europe colder, a weakening Sun, all will be fine....should we get the synoptics !

Lorenzo, I’ve got high confidence of the loop of High pressure forming from near the British Isles towards Scandinavia bringing an easterly flow of some sort, everything else that I’ve seen this morning then supports an established High pressure. What we didn’t want was an ‘end of the line’ easterly such as Xmas 2005 where no sooner has the flow become established, the Atlantic is banging the door down. The only doubts concern orientation of the High going forward from around the day 6/7 timeframe. Shortwaves could appear that result in the block not being able to get that crucial orientation, but that is just speculation. Importantly we are not relying on the Arctic High to get where we want to be – we look back at Jan 87 and saw what a part that played, but since then relying on it to intervene as always ended in tears for future cold spells. Looking good, but the next 36/48 hours are important for the models, and I think that, worn down by so many failures, if 2009-11 had not happened, nobody would believe that this was going to happen until it is T72.

It hasn't started yet !

The North Sea is still (relatively) mild in December and this would modify the easterly flow, no matter how long the draw is. I don't think it would be a problem for inland areas (in terms of snow).

Yes, the block gets into a great position. I would prefer to see the core of heights further North in the T120-156 sort of range, but this can and will change run to run. Looking forward to the METO update, they will be guided by their own data which we don't see but the 0z runs and ensemble suites must put pressure on them to change from yesterdays summary.

Tomorrow is one of those where the less cold air gets in ahead of the PPN, so for low ground in England I would think mainly rain with perhaps some sleetyness. As for the easterly, the ECM offers the very best solution, I would think snow showers and organised bands of snow would push right across the British Isles. But no point in looking at those details yet.

I find that the UKMO at T144 does often play catch up, but others will point out that it's refusal to join the easterly party has been vindicated in the past. GEM supports the GFS this morning.

Well JW, the train isn't coming until you can see the train. I was looking at the GFS this morning and my only slight criticism was that I would have preferred to see the core of heights a little further North to allow for greater instability underneath the block for larger portions of the UK - then the ECM delivers exactly that ! Not sure where the UKMO is going with it's shortwave at T144 but I will put that on one side for now. The key developments to form the upper High to the NE of the UK are ALMOST in the reliable timeframe, so yes a step forward this morning. However, it has all gone wrong for easterlies before with cross model agreement at T96-120 so caution advised.

It isn't Chris because the energy is going North, milder air would get ahead of the PPN. You would need an Atlantic attack to be negatively tilted or at worst vertical to get widespread frontal snow. Anyway, hopefully academic and not happening !

We would not want that T240 to verify, the Atlantic would come in, block to the NE retreats/sinks and the Azores High would ridge NE. T268 onwards would be +ve NAO charts.

Yes it looks a little strange, the worry is that heights are already retreating at Northern latitudes between T168 and T192 and this is the second ECM run to really crank up the PV at the end of the run. Thankfully the ECM at T192-240 has been as inconsistent as any other output over the last few weeks, but as Dave says, what is being shown by the NWP overall is a fair way from an unstable easterly flow spreading West across the UK.

What is going on is a complex battle and minor changes lead to big differences later on. The GFS gets there after a protracted battle, and our location means that this sort of battle is always likely to take place. A few hundred miles either way with the pattern and everything changes. Nice undercut going on at T288 !

This looks much better, there is potential great WAA for the Highs to form the loop needed.

The METO are talking about wintry showers in far Eastern areas with rain and milder weather at times in the far South and West. Hedging their bets a little but they are obviously see as it being an end of the line easterly at best. That sort of situation won’t sustain for long and by synoptic implication the block will not be aligned how we then need it to progress an easterly across all parts. We would then have to have the retrogression to Greenland that GP is talking about to keep us on the cold side of the PFJ.

The 06z is going the wrong way, shortwave has popped up over Norway and the core of heights is over the UK with, I would think, little chance of the necessary curveback to get the right orientation of HP.

Interesting, however is the 32 dayer any better or worse than anything else we see from the NWP ? Shouldn't we now be seeing a strong height anomaly to the South of Greenland if this had been correct 2/3 weeks ago ?

Heavy rain, one of those horrible Cheshire Gap days today.

A messy GFS this morning rather like pulling teeth, one of the potential problems is that a UK High sets up on it's own detached from the Height rises to the NE and shortwaves prevent or delay a link up. The ECM (and I think the UKMO if it went further) present a risky route to an easterly but clearly this is not going to be simple. It never is.

That's a very good set of ensembles, if you look at the T144 position, the OP is a solid run. Some members bring in an easterly quite quickly (at least for De Bilt) but note how many go pear shaped later on with a perceived bringing back of the Atlantic. Literally just 2 members. If you view it on wetter, I would suggest a T216 or T240 would see a looping of the UK High with raising heights to the NE.

Yes, the ECM has zero margin for error, it's a potential shocker at T144 and virtually the same as the UKMO but because of that amplification we see heights rise to the NE and ultimately an easterly. Caution required, we have been here any number of times and we saw last week how energy spilling Eastwards became a game changer at around that always crucial T144 time period.

Thanks Ian, do you think a November 28 2005 type development is possible, which rather caught the METO out ?