Well I had no idea about GFS going all the way up to 1hPa, so my impression of the model has now changed a little.

I guess the overlooking of the the upper-level wave 2 warming lately is down to the model physics. There is also a lower warming, trop. driven, which is all that GFS has been showing lately. The upper warming, which takes things so much further, has finally been picked up on the GFSP 06z but that was quite a lag behind ECM and JMA:

http://modeles.meteociel.fr/modeles/gfsp/runs/2014123006/gfsnh-10-216.png?6

At last we see some significant depletion of the Canadian vortex lobe, after so many runs insisting on maintaining it until some 2 weeks from now.

A weak, distorted vortex does then shift back to Canada but two waves of warming continue to put it under a lot of pressure:

http://modeles.meteociel.fr/modeles/gfsp/runs/2014123006/gfsnh-10-288.png?6

This leaves very little in the way of a vortex by day 14.

This is a huge improvement from previous GFSP runs and much more in line with recent ECM and JMA efforts, though ECM has been keeping the polar vortex more toward Siberia days 9-10.

Meanwhile, GFS remains more progressive with bringing an end to to build up of warming and moving it away from Greenland once into lower-res output. This means the vortex returns to Canada very quickly.

If this warming manages to take down the Canadian vortex and prevent any real recovery in the 10-14 day period, there may be a trop. response by mid-month in the form of low heights draining away from Canada. Once again the ECM op run has dropped a hint of this on its day 10 chart. As for the EC32, I can only imagine that it doesn't suppress the Canadian vortex effectively enough for much of a trop. response to occur.

If an actual SSW occurs from this warming (still uncertain) then the consequential increase in high latitude blocking would be seen some 3 weeks later, as clarified by Ferguson and helpfully posted by Neil earlier. That actually puts us down for the final days of January.

I must admit, I got my lag times for the effects of the wave 2 warming itself jumbled up with the lag time for a SSW yesterday so was starting to envision a big increase in high latitude blocking by the end of the third week of January.

Now I see that, unless a SSW occurs and propagates down unusually fast (not out of the question I think, but clearly not being signalled for by GLOSEA or the ECM ensembles), a shift in the emphasis of low heights out of Canada in favour of Siberia is the main chance of getting a colder pattern as early as that.

To summarise the above in terms of conditions down near the surface, we're talking a strong likelihood of zonal conditions for the first two weeks of January, which might feature a gradual lowering of temperatures in the second week (suggested by recent ECM runs and evident on a number of recent GFSP runs), the extent of this not at all clear but unlikely to bring more than transient cold conditions to the UK.

For week 3, current guidance suggests either more of the same or some degree of increase in the extent of colder incursions, but really the signals here are too weak to make a call of any sort.

Week 4 is where the SSW wildcard comes in. Best left to one side until we know if one is actually coming later in the first week of January or not.

As I keep saying, I'm following the strat. stuff closely because it's far more interesting to me than the current trop. output which seems to become even more tedious with each new run as the jet seems to be adjusting further north - not even any severe wind events down here within the next 10 days. I enjoy analysing the more interesting aspects of the model output and at the moment it just so happens to be up in the stratosphere.

Having said that, I have noticed that GFSP and GFS are by far the worst to look at, with a deep vortex to our NW days 8-10, and this is not supported by ECM or GEM which shift the focus more toward Siberia.

The GFS and GFSP solutions are a consequence of having a single, intense storm to our NW in 6 days time which then stalls and builds a bit of a ridge ahead of it, after which a new low off the U.S. phases with it and creates the deep trough near Canada.

ECM, UKMO and GEM don't have such a strong system, which keeps the jet flatter and allows the storm to get further east before the new one off the U.S. catches up with it.

To what extent that ties in with the strat. evolution in each case I'm not sure, but they do mirror each other quite well.

So concludes today's short essay 

Fantastic post storm-chaser detailed and informative and that even answers the questions to my previous post cheers buddy,

Less cold is more appropriate Jacko

Yes, we know

Edited

GFS models at these levels in its output:

1,2,3,5,7,100,125... then at +25mb increments down to the surface.

GFSP at least the same.

Traditionally as I'm sure you know the 500mB charts have been considered the most useful for forecasting the long wave pattern. In the last few years the strat has been incorporated into the seasonal models and consequently more attention to it is paid in the medium range numerics. Whether that attention is justified or not I don't know. Personally I like the 500mB charts.

Yes indeed! Who would want rain and wind and floods!!?

Everyone I have met saying drier and colder is far more appropriate. - Nice this cold spell has killed the bugs and pests!

Thanks for the info Brian 

500mb is a good level for forecasting as it's high enough up to avoid the effects of frictional forces, improving predictability, but not so high that surface responses lag behind.

Higher levels can give a guide as to how the 500mb heights might evolve in the future, but this does rely on the stratospheric setup being able to propagate down to the 500mb level, which seems a bit hit and miss, and current understanding seems inadequate for reliably predicting whether downward propagation will occur... let alone how rapidly.

If we could get a better handle on that, the strat. would probably increase the accuracy of longer range forecasts in terms of month-to-month trends in the 500mb heights, but in my opinion the finer details of placement (e.g. will the trough be over Canada or Alaska?) are unlikely to ever be reliably predictable beyond a few weeks ahead.

So at this stage the strat. stuff is highly experimental, based on theories constructed from analysis of past events. For all I know it will prove as effective as throwing darts at a map of the world while blindfolded, in which case it will be a shame but I will have had a good time following the strat. charts regardless 

you old rogue LOL

😄

So Goon, your pinning your hopes on a SSW event?

That would be a foolish thing to do mate, I am not a great believer  in a certain thing being needed for Snow, there are so many other things that come into play.

I personally believe its swings and roundabouts, prior to last Winter I had four on the trot that gave me good falls of snow.

Winter and snow will come again, I am sure . People really shouldn't be surprised we are on an Island that is sat in a bath of warm water ( so to speak ) with a jet stream coming West to East, we don't really get a chance until the Jet Stream decides to something out of the norm.

Just looks like fairly  normal  winter / "Atlantic full on" mode to me

In its  own way, last year   really was as unusual as a 62-63 winter.

http://www.wetterzentrale.de/pics/Rtavn37217.gif

I think it was a fair bit milder though

Fair play Marcus.

I have watched Gavin's excellent video and read Brians winter forecast and both say there is a strong possibility that the end of winter has a better chance of producing colder conditions than the start, so you may get to see some action after all. I know that there are many factors in producing a cold spell in this country, but for me the jet and AZ high are two big driving factors. Without them playing ball, well it's futile really.

, 

Here. alas, is one output which will back you up for the week after next:

http://www.wxmaps.org/pix/prec4.html

yes DEW, not looking good is it? I suspect there would be some flooding around if those maps came off.

the difference being that there would be a lot of cold air wrapped up in that system . . . .

 Showing below average precipitation in week 1 and slightly more during week 2.

replying to DEW "week after next"

😉

http://www.wetterzentrale.de/pics/Rtavn2161.gif

Feeling cold with plenty of wintry ppn coming through