...so a <10% change overall generally for the other models, in comparison to default swings. 

Sorry, I deleted it because Darren had made similar points.

I find this graph useful - it shows the 60% and 80% accuracy thresholds over time.  ECM and GFS models have improved steadily (and UKMO but only for part of the time).  Noticeable that ECM consistently outperforms GFS on both measures.

This is northern hemisphere only - there's another graph for the SH

Yes, a shift to later in the month for the 'increased likelihood of colder weather' - but the caveat seems largely unaltered.  There was always the rider than milder, wet and windy interludes were possible.

 One starts to wonder if the MetoO 16 to 30 dayer  will still be talking about a transition to colder weather in July.

Probably April, just as the new cricket season gets under way....

It's interesting how the Met Office has delayed the possible colder weather because this morning several of the experts in the field of SSWs were being more positive about the impacts appearing after mid-month.  Having said that, the guidance was also that the models don't handle the effects until they've worked their way into the upper troposhere and they have some real data from which to extrapolate.

If that's true then we shouldn't expect the models to start to reflect the SSW until next week.  Do you agree?

I suspect it will update in a few days to say that the established colder conditions are likely to continue however milder conditions are stilll possible at times. 

Anyway back to what the models are actually showing and it’s nice to see that the first of the 12z suite available, the ICON model, ends on an interesting note. http://modeles.meteociel.fr/modeles/icon/run/iconnh-0-180.png?02-12

Will the GFS op or GFSP (out shortly) continue their earlier N/NEly trend? And will people still complain when the midmonth cold spell is not shown around the 10th or 11th? 

A beautiful ICON run just now - it shows our current blocking high morphing into a perfectly-placed omega block in a week's time.

http://images.meteociel.fr/im/7648/tempresult_ugm4.gif

(Not sure how long the link will work for, but it's an animated GIF showing the evolution.)

GFS 12Z appears to be going down a similar route.

The UKM precautionary tone is totally justified IMO, but does not rule out a fairly quick response in 6 days time.

Our friendly neighbourhood high has been around for so long it’ll be a shame if it doesn’t lead to something itself.

Interestingly both the UKMO and GFS 12z output are now toying with idea of cooler air from the north at around day 6. A bit of a change on earlier runs but I’m not sure how or if this will have an impact in the GFS outcome down the line.

I feel we may still need to wait until midmonth for the proper cold.

Not much cheer from GEM this afternoon 

There never really has been in any consistent way so not much change there. It would be a day or two after that, at the very earliest, that I would expect something more encouraging from the GFS if the trend is to continue.

Not entirely convinced by the argument. The NWP models the strat and so the impact of the SSW has been factored in for a long time. However, it is possible the SSW event will reduce the NWP accuracy (and so increase forecast uncertainty) because of the way the pressure blocks are shuffled. 

PS: GFS 12z has some interest in the 120 range but it still goes for a jelly high.

Looks like GFS is getting there at 300h. 

And once again the GFS looks like producing something very interesting midmonth. Anything before this point is a bonus and not really modelled http://www.wetterzentrale.de/maps/GFSOPEU12_312_1.png

Before anyone says it I know that chart in itself doesn’t show cold. It is what comes next that’s is the interesting bit. 

Edit: based on the last two or three days th GFSP may possibly go for a more extreme version of this scenario (again).

I hope we do get a northerly for once - it seems such a long time since we last had one, or at least one with teeth, the sort of thing that doesn't lead to 9C at noon down here.

From what I can see of the models, a "diving low" scenario keeps cropping up. It's in association with the polar vortex rearranging itself as part of the SSW after-effects and it's very different from the normal "lows moving NW between Scotland and Iceland" zonal scenario.

I did think a couple of days ago that the Met Office's milder, wetter interlude was on shaky ground (as the high was looking llke hanging around for literally weeks), but there's been a definite move towards the lows plunging SE'wards scenario. As several runs have shown (including the GFS(P), most consistently), not only does that result in a potent northerly, but a NE'ly or even easterly as the lows eventially clear away to the SE.

There's still a lot to be sorted out, but to me it seems the transition from "jelly" high (to use Brian's phrase) to unsettled and colder (in the north) to a much colder spell is gaining ground. And if it continues to do so, full marks to GLOSEA and the Met Office for picking up on it.

Another one to add to the ever expanding M.O dictionary. 

Control gives a good northerly day 6/7 but then goes flat.

GFS Para is sadly flat this time in fact most of the GEFS are underwhelming. 

Quite a bit of support for a cold plunge around January 9th now with 8 members now going to -5C or below in a week's time.

http://www.meteociel.fr/modeles/gefs_table.php?ext=1&x=&lat=51.5085&lon=-0.12574&ville=Londres

In the long run only one member fails to reach -5C.

Are you looking at the latter parts (mid month) on the 12z run? 

It’s probably one of the less extreme versions of the scenario but the theme is the same, and not flat.