Ian Brown

If this were the GFS I would say it was about to set-up one of it's outrageous Northerlies !

A most progressive 06z, and we would be looking down the zonal barrel for some time should this verify.

It's only brewing for us if we can see High latitude blocking, which at the moment is not on the cards.

Light rain here.

It's going to topple over the UK as the core of heights is too far South in the Atlantic. Not that it matters at T240.

Yes John, when people talk of a reset ie to zonality they need to be careful what they wish for as such set-ups can last weeks and months.

No, often this can actually be unfavourable for our pattern.

Yes, certainly the US guys are seeing a very flat jet across their part of the World for December, so as the models indicate by day 9, we should see those low pressure anomalies begin to disappear over S Europe as the High sinks and we enter the next phase of zonality – the last one lasted exactly a month.

Yes, gone are the days of expecting snow and getting rain, and vice versa.

Thats because that output was at T200 plus and is always liable to wild swings !

A progressive 12z with a strengthening PV, we are hanging onto the settled conditions by day 10 but the Atlantic is banging the door down.

Well the first thing to say is that the models are not showing mild at T144 or even T240. However the point by Shedhead is correct, if the models do start showing mild at T144 or T168 from the position of mid-latitude HP, then it is highly likely to verify. Why ? Well it will be because the High is sinking into Europe. If the sinking is going to happen, as suggested by the METO, then the models have a margin for error of several hundred miles as the jet returns over the declining block and though specific temps and rainfall are not easy to define at T144, the general pattern is. Now take an easterly and the setting up of that, effectively suspension of HP rather than sitting, and one wrong move and it’s over or heavily diluted and this can go wrong within T72-96.

Yes, HP dominated models this morning with just slightly differing positioning on offer. Whilst we maintain the low heights over Southern Europe, a sinker can be prevented but the models are cranking up the PV later on.

Wet snow now falling, bit of a Cheshire gap flow of showers setting up.

I thought the MOGREPS was the model least willing to go with the failed easterly of Dec 2012, if we are talking about the same episode ?

He is if you take that mean at face value - you can't get HLB from that specific chart, but given the scatter the ensemble mean is just that and it is a long way off.

Waiting for a High to sink is a great time eater because not only do you have that, you then have the zonal phase that is going to follow and last X number of weeks. That said, we don't know that that is what will happen. We are speculating on shortwaves at days 9/10 and there is a whole lot that could happen between now and then even though the 3-7 day outlook is benign.

ECM at day 9 and ideally you would like to see the HP centred a bit further North but at least ECM has been fairly consistent in the way it handles the High from T96. I feel that the GFS is possibly barking up the wrong tree with its intense build of pressure to the West, but more runs needed.

Sausages for breakfast from the ECM: http://www.meteociel.fr/modeles/ecmwf/runs/2013111800/ECM1-240.GIF?18-12 Quite a different run before then too with low heights plunging into Europe compared with the GFS which is a HP fest. As we know though with that ECM chart, you can't bank those at T96 never mind T240..

I don't dispute that Phil, but obviously the question is what happens next from day 10 onwards and the GFS sees the jet pressuring the Rex block .

I remember this let down and watching Countryfile with a little bit of surprise at the forecast. Without the benefit of computers impossible to know what went wrong, but I don't think anywhere had snow from this one. We will never know what exactly what went wrong but the actual never suggests anything like the forecast unless you were on a hill in N Scotand : http://www.wetterzentrale.de/pics/archive/ra/1993/Rrea00119930124.gif

Yes, this was at the time when the jet was rampant to our NW in the winter periods, so that HLB could not be achieved, hence given the right setup, the cold was sent in no particular order to Eastern Spain, North Africa, Cyprus, Greece, Turkey and as Kev shows even into Israel on that occasion.

It's a different NH profile from the ECM, but even if you take days 9 & 10 at face value there is no guarantee that you would get the orientation needed to advect the cold uppers towards the UK. The ECM has often been guilty of falsely building heights towards Greenland in the past in the outer reaches of the output.

I think as has been alluded to wrt the Strat, the impact of the cooling will be felt with the PV strengthening. Only low heights in Southern Europe can then save us from conventional zonality.

Yes a very similar picture to it's earlier runs today showing mid-latitude HP out to day 10.