swilliam

More pertinently perhaps the Azores high is linking to the Scandi high - probably best not to say what is good or bad as well and just see what happens.

Yes it is interesting that one as it does not really come about due to trough disruption and a slider low but due to several bouts of WAA further and further West extending the Scandi ridge westwards. This is I think is why it is so cold.

But does eventually - shows we will be most unlucky not get something good (cold and snowy) out of this

Control run is having non of it Shows that it is still finely balanced.

A bizarre post - does this not equate to cold weather - most of the UK below -8 uppers What exactly are you expecting/hoping for?

Much larger WAA from the Pacific into the Arctic on this run - wonder what effect on the later output this will have?

It seems to me that the drop in the ensemble mean is due to cold zonality rather than any true arctic or continental outbreaks (although there a few topplers). This is presumably due to the happenings on the other side of the arctic with the large HP there pushing the PV that is moving towards Scandi towards us and therefore moving the jet stream further South. This can be seen on the mean hemisphere chart A good example is number 3 This can also be seen by the fact that no member reaches -10 until the end of the run. Unless the Atlantic high links up with the Arctic high I cannot see any sustained or very wintry spells happening in the medium term (although way better than it has been)

When I posted an ensemble mean map for 15 days time you told me it was as good as a chocolate teapot - is that not the case this time?

There is not a desperately large amount of support in the ensembles for the PV moving to Scandi as shown by the mean at t360 (some of this is due to reforming of the pv in this position though). A few nice perturbations though as expected 16 17 18 Let's see what tomorrows runs bring

Yes but the GFS high res finishes at 192 so we should not expect this to be in this part of the run. This is better than it not being shown

You can get them here -http://www.meteociel...es/archives.php goes back to 1871 somewhat unbelievably - and you can scan 15 days at a time seeing how things evolved - fantastic resource - much better and easier to use than the wetterzentrale charts

Yes Nick but a few weeks ago even in the far reaches of the GEFS ensemble there were no perturbations showoing anything interesting at all - all that is being said is that at least there is potential.

The 06z control run looked pretty uninteresting (from a cold perspective) compared to the 0Z. That is until the end of the run when an amazing arctic high is in place. Shows what might conceivably happen with the forecasted weakening of the vortex allowing high level blocking to develop - we just need it to do so in a favourable manner for us.

Interesting control run as a route to cold. At t192 high pressure right across the pole from Russia to Canada (and splitting of the PV). leading to a significant northerly when the Atlantic high links up to to this. Followed by some good snowfall chances Hopecasting of course but better than looking at endless zonality in FI. Bottom of the ensemble though (or top as you see fit)

People always say that the models are more accurate during zonal periods but the latest data on model accuracy does not support this. It can be seen that the verification rate was at about 0.9 a few days ago but has dropped to nearly 0.7 for all the models during the current mild spell. I think we believe they are more accurate during this kind of weather (uninteresting mild mush) because we skip over them. When they are showing cold and especially snow we examine them in every detail and criticise them when they are slightly out.

Bit more interest on the 06Z with a high developing near Iceland Didn't last long though!

I do not believe he mentionedt a Scandi/Greenie block - all that was discussed was a linking of the mid Atlantic ridge (currently shown on the models - i.e. the ECM) with the Western Russia high after the end of that run - not such a fantasy evolution and shown in several of the GFS ensemble members e.g

He was not referring to the same timescale as John - clearly what JH said is likely to benearly right and nothing much will change in the next 2 weeks other than the details.. The speculation provided on the video was outlining a possible scenario beyond the timescale discussed by JH (who would not speculate beyond a couple of weeks).

Looks likes signs of the PV splitting somewhat on the ECM

We have just established that using a chart (the same chart in fact) at T384 is hardly illustrative of what might happen in the future

If you want to see how this could happen then view today's CFS output. This is New Years eve Not relevant to the forecast I know but shows how it can happen. In this case it is the usual method of rising pressure in Russia (well away from the UK) followed by repeated WAA further and further West

No it does not deepen the low anything like as much - unfortunately the GFS has a habit of overdoing this.

I think you would find that there would be plenty of discussion about the nearer term if there was a cold spell imminent (or indeed if one was ending)

Looks like a cool period though - especially bank holiday Monday. The high that moves in on the ECM looks like a typical transient winter cold high. Would be pleasant enough but of course still FI

Gosh someone posted a chart to back up their point - thanks.