cooling climate

The spoiling shortwave over Iceland at approx t132 onwards will become less of a feature I think as we get nearer the time frame which will make a big big difference to the output of the run. The parallel run is already weakening this feature so hopefully this will become the trend. Quite pleased with the run otherwise up to t168 ish.

Encouraging signs as heights and WAA building further west at t108.

Very encouraging output again this morning, is this the start of a backtrack from the models this morning? I think it is. I think we will see a trend from the models to build much better heights to the north and northeast as the Arctic high comes into play. (The Arctic high is the major player here). The troublesome shortwaves modeled at the moment will become less of a issue or disappear from the output altogether. As GP has said because of the easterly momentum from the Arctic high we should see everything back further west allowing for better heights to the north. Here's to a very cold outlook.

At this range, remember we are talking 10 plus days away I would be very surprised if the models had the pattern nailed. I would not be at all surprised to see the models revert to a very cold pattern again tomorrow or monday. This is not just wishful thinking, Arctic highs are notoriously difficult to model plus any shortwaves at t120 could very well disappear altogether once it gets inside the more reliable time frame. Nothing has changed my mind yet that the pattern is not going to change to a much colder and wintry one. If by Tuesday the models have not started to backtrack then yes maybe will have to be a lot more patient.

I think we are all use to the wobbles the GFS model has at times where it will drop an idea and then pick it up again. Also if the model has an inherent flaw in overdoing shortwaves then this would apply to the ensembles as well I would have thought. The 12z ECM run should give us a better idea on weather the GFS is right or not.

That is from the 06z run this morning. UKMO looks good to me. Very good.

Convection still looks strong and progressing across the date line going by the OLR anomalies.

From what I have read this is a warming from the top down or at least 20-30mb heights the warming rises to these heights then due to lower density the warming expands and starts to descend again. Anyway quite agree that we do not want a pattern reset ( I'm thinking Jan 82 no good the pattern collapsed and that was basically it). That is why I am hoping the ECM 0z run is correct in as much that at t240 we still have 1050 heights over the pole where as the GFS has the vortex returning to the pole.

I think a warming is or has already taken place and this is what is causing the ridging and higher heights over the Arctic and the split vortex to occur.

Surely its this now that is causing the vortex to split. A SSW is already or about to take place.

PTB 9 trying to nudge -18c 850's into the southeast corner.

The parallel run does the same breaking down the -AO with some of the vortex returning over the pole and the heights sinking back into n/e Siberia. Is this a new trend? One to watch for sure.

The 06z run although very cold turned out a lot messier and not as good as I imagined the reason for this was a low development over the pole at t180 thus cutting off the heights over the Arctic and everything sinking south. When you consider that the 0z at this time had a 1040 high over the pole I suspect that the GFS may be up to its old tricks of developing to many shortwaves only to drop them on the next run.

The 06z looks like being a absolute cracker of a run.

I noticed the GEM model has low pressure around Svalbard at t132 which would stop the high ridging north and the WAA. No other model agrees with this. The 18z operational GFS had this last night but the 0z ditched it and so has the 06z.

Excellent runs this morning. The ensembles should continue on their downward trend now. I really can not see anything other than a very cold pattern developing across Europe and the UK. Their may possibly be the odd hic-up that may slightly delay the onset of very cold weather but that is all. Very good model watching to come I feel.

PTB 17 t324 onwards. Yes please.

The parallel run still very much game on. Biggest difference I could see on 18z compared to 12z GFS run was at t240 on the n/hemisphere charts the 18z had a 1000 mb low while the 12z had a 1040 high over the pole.

GP could well be right but I would not be surprised to see very cold weather impacting Europe and the UK from the 15th, 16th onwards then getting progressively colder. If the operational ECM is correct then four or five days later than this.

Sorry what I was trying to imply was that any cold spell before Christmas and bookies will slash the odds of a white Christmas. I know its way to early to predict a white Christmas, cold spell or not.

The shortwave being shown by the ECM may or may not be right, we know what the GFS is like with shortwaves so one to watch over the coming days. Even if the ECM is right, as others have said this will only act to delay rather than scupper any very cold outbreak. Seriously I would advise any one betting on a white Christmas to get their bets on before the bookies get a whiff of this otherwise odds will plummet along with the temperatures.

The heights to the north are there, look on the n/hemisphere charts and then compare to the operational GFS run. By t144 on the UKMO run the low in the atlantic is already backing west as pressure rises to the south, another good run.

A very quick flick through the ensembles on meteociel and a good few show a easterly or northeasterly etc with blocking to the north. I wonder if Steve Murr is going to give an in depth view of the 12z or perhaps he is hedging his bets until the ECM run is in. I myself am very confident that the ECM will back up the 12z GFS run. With such a strong signal coming from the models now I think we are only a couple of days away from the models just dealing with the details rather than will it or wont it turn much colder.

This run has the hall marks of a classic.

If you look at the pressure charts for say t120 the high pressure over Alaska is most pronounced at the higher levels of the stratosphere then working its way down. IE rosby wave breaking = SSW event from the top down. 10hpa t120 100hpa t120 The warming area expands due to the lower density of the air as I understand it but then radiative cooling acts to address the anomally.