Cheshire Freeze

vs climatology at that range, this is one impressive ensemble mean...384 hrs One even gets the impression that the vortex could blow itself apart some time in January given its (very) quick departure from a slumber throughout November...as some have indeed hinted in the strat thread. This is something which wasn't looking likely initially i.e with the continued depressed vortex forecast for December. Hence a slow decline into mobility was initially more favoured once the sluggish vortex phase ended. It's no wonder the modelling and pros alike are having a torrid time thus far. The odds of a more sustained severe spell of winter weather sometime during the core of winter have shortened IMO.

Well the GEFS at extended range are perhaps one of, if not the, most promising suites I've seen thus far. Heights getting to an increasingly northern latitude is a common theme- along with the much touted retrogressive heights Bang on cue too...i.e Christmas- New Year week

CFS Jan anomalies just where we want 'em

The thing I notice there is the elongated core of the PV. For once not stretched in a way which precludes cold for us. Could easily see an easterly set up out of that going forward. Even further on into the extended range, the overwhelming signal within the GEFS is for the Canadian vortex to start to run out of steam (which should thwart any meaningful zonality)...what was that Bluearmy was saying about 4-6 weeks of zonality being 'poppycock'....

''a marked switch away from -ve NAO 2nd half of winter'' Well to see a switch away from a -NAO we'd have to have the -NAO first Not a chance this month will return a mean -NAO

It's a recurring theme deep in FI. Need to see it start moving closer now. The GFS/GEFS are determined to build a wedge of heights to our N/NE towards Christmas.

It isn't up for debate as far as I've seen IDO. However what is up for debate is the latitude the high can gain traction to, the orientation of advection on its western limb and how much falling of heights we can get across Europe. What may seem like minute, insignificant vagaries within these parameters will have large ramifications going forward towards Christmas (seeing as we're still being trop led). Given your vast expertise on all things meteorological, I'm surprised that you cannot see this?

At 384 hrs in last night's 18z GEFS there was a cluster of approx 50% that had significant N blocking or imminent potential. Can this suite get close?

Yes, this! Look at the angle of advection on the western side of the block... May not impact us this time round but it will have consequences going forward...as I keep saying.

Meanwhile GFS control gives it a jolly good go..at just 120 hrs And, I think me and you both know that GEM would be far from flat 48 hrs on from that chart!

OK- so that isn't a particularly impressive block but I ask you...was the Jan 2013 block impressive in terms of absolutes? No. Also I'm highlighting it because such a scenario (with much more impressive MSLP numbers) has been floating around the GEFS for a couple of days. I genuinely do not know whether your aim on this forum is to act as forum WUM but you do sometimes convey a strong sense of wanting to be so.

Christmas-New Year week ; )

It'll be Monday...was last month

I'll take your day 12 and raise you day 16. A repeating trend towards last week of December and as I said above, given the continued propensity for the Azores high to ridge NE, it was only a matter of time...Charts like this are continuously being signalled within the GEFS so there is a signal there somewhere as we look towards Christmas.

Hmmm I do get the impression that it is only a matter of time before the continued interference by the Azores high and repeated block signature to our E/SE buckles the jet sufficiently to promote enough WAA to allow Scandinavian heights to build

Starts off at about 0C at 850 level Knocker- small blob off Norfolk Rapidly expands and cools to just about -4 some 18 hrs later

Between 192 and 210 hrs we actually begin to culture our own cold pool...a reminder that even an island at this time of year at this latitude can see such a phenomenon. From about +1 to -4 at 850 level in a day

FI will be interesting. The best FI synoptics have tended to follow the slightly more amplified closer time frames.

Ahhhh but the 850s don't always tell the whole story Feb

I've run through the individual perts at 384 hrs. 50%- yes 50% have some form of appreciable northern blocking or immediate route to blocking. That's a significant cluster.

Here is the 18z MEAN at 384 hrs...there must be decent members in that lot (I haven't yet checked) but what I find impressive for a mean chart is the whiff of disruption to the trough in the Atlantic

So, those knock on effects I mentioned... A much more hopeful end to FI than the abomination that was the 12z (effectively a jet circling tightly around or just N of our latitude) It's essential now that we eke out as much as we can from that block in the short term.

It'll have knock on effects going forward though further into FI...you can see the difference across Europe straight off by day 10. It might just be variation within an envelope but everything has a knock on effect further down the line...especially when we're talking about a trop which is supposedly still disconnected from the strat. Every last ounce of amplification needs to be squeezed out- otherwise we end up like the 12z FI.

Snow into the W by 216 hrs