yes a significant shift as you say, plus with the ENS painting a dire picture there is little on offer if it’s cold weather your after. I said a few days back that IMO we are entering a crucial phase for this winter, if the SSW does not propogate as forecast then there could be big disappointment- and even if it does materialise it does not necessarily mean it will impact us as some hope. 

My best guess for Christmas would be quiet and cool, some sunshine though frost early and late where skies clear. Thereafter anyone’s guess. 

Compare that with the GFSP for the same time though, and it's a different story. Both GFS(P) and ECM show a full-on split happening, which boosts the chances of (but still doesn't gaurantee) a proper cold spell in January.

NB - GFS(P) has been rock-solid on a split over the past few runs, whereas GFS just shows a displacement. The knock-on effects of the two options would be quite different!

The temperatures look a lot lower than they were back in Feb, though - in February there was nothing but pale blues and greens across the northern hemisphere for several days!

I'm not sure that this has anything to do with it, but by the time the SSW in February this year took place, we were nearly two months further into the process of the sun working its way northwards and, in turn, the days lengthening.

Indeed, but the thing to consider is that the vortex usually weakens throughout February. At this time of year it should really be ramping up, reaching its peak in early January.

As can be seen in the link below, the GEFS is actually showing a record reverse zonal flow for the time of year.

http://weatheriscool.com/index.php/stratosfaren-zonalvind-10hpa-60n-gfs-ens/

(The February minima were set this year, of course!)

This is very interesting.

Some interesting changes this run:

http://www.wetterzentrale.de/maps/GFSOPEU12_177_1.png

Compared to

http://www.wetterzentrale.de/maps/GFSOPEU06_177_1.png

It wouldn't take much tweaking from here to deliver something interesting

It doesn't really deliver much further into the run. But the ridging looks better. It give us something to hold onto mind.

I don't think we can expect to see any northern blocking appearing in FI for another week or two at least, given when the SSW is modelled. As far as I can see, the warming pushes a very strong vortex over towards Canada, which is what we are seeing at the end of the current GFS run, with a very flat zonal pattern due to very low heights over Canada and Greenland.

If the vortex does end up splitting then maybe we will start seeing blocking appearing in the second half of January. But the charts currently only go out to Jan 4, so it will probably be at least 10 days before we start seeing the eye candy.

Just my thoughts, not meant to be expert opinion!

Thanks Rob. I am hoping whatever happens something delivers next month - that being said, something is different in the 12z ensembles

Interestingly I have taken a look through GEFS and I have to say there are a number of runs now toying with something different next week in the 144-172 range.

P7: http://www.wetterzentrale.de/maps/GFSP07EU12_138_2.png

P13: http://www.wetterzentrale.de/maps/GFSP13EU12_138_2.png

P14: http://www.wetterzentrale.de/maps/GFSP14EU12_138_1.png

http://www.wetterzentrale.de/maps/GFSP15EU12_138_2.png 

This idea is not without support. This I feel is a significant change the 00z and 06z run. None the less, could all change again

There really will have to be a massive flip in the output  for any significant cold in the next 2 weeks. Think its very unlikely . Mid January different story though.

Having said this the GFS ensembles just starting to look a bit interesting not many but a few good ones P10 the best!

Looks like either a cold a mild-ish high.  I think a mild-ish high is more likely to hold position up to the turn of the year.

Plenty of unresolved features all around it.

This could end up a very interesting few days model watching....

Yep, I'm not trusting any NWP as far as I could throw it until the mid range is resolved. A look at the ECM 12z Op compared to GFS et al tells you everything (or nothing...)

I think any early pressure rise north of the UK is almost guaranteed to be steamrollered flat as the vortex gets squeezed across to this side of the pole by the warming taking place in the next few days. I would expect to see pressure anchored well to our south until the second week of Jan or so - maybe if HP hangs on in the southern half of the country it might be reasonably settled but I don't think we can escape a couple of weeks of deep purples on the charts to our northwest before anything exciting happens.

What is becoming more and more clear IMO is that early next week seems to be about the limit of the reliable range when it comes to forecasting the weather at the moment, based on my observations of today's output.

Going back a few years, somebody used to do a review of the accuracy of the GFS, ECM and-I think- MetO forecasts at some time out (\I think it might have been T+120, T+ 144 etc). Was it Gav or GW? I used to find that comparison worth note, and wondered if it had time-of-year patterns too; i.e. was GFS more accurate at +120 in summer? Etc.

Does anybody else remember this, or know why it stopped?

Model accuracy stats are always available here:

http://www.emc.ncep.noaa.gov/gmb/STATS_vsdb/

Thanks Ben.

I’m not convinced the relationship of the temp at 10hPa and at 500hPa is as simple as that Rob. They aren’t always stacked like that. We really don’t know how the warming and displacement is going to affect the surface synoptics and we have MJO phases etc to add to the mix.

I agree it’s not looking too promising with respect cold shots but the NWP can flip rapidly. 

At times like these we need to put faith in the professionals and concentrate on our careers. 

It’s looking more and more likely that we’ll see a split rather than a displacement now, I think surface cold under a U.K. high being the holding pattern until we see the trickle effects of the above. I wonder if we can get a sustained well below average January under our belts?