Met4Cast

-15c 850hPa temperatures into Shetland on this run. Shame the azores high is having such an influence, SO close..

This chart is incredibly frustrating to look at Greenland High. Huge Scandi trough/cold pool UK mild because of the azores high & actually under an almost zonal pattern.

Good agreement between ECM/GFS at day 10

There is some snow across the Midlands on the ECM though it's not exactly a whitout - Snow showers following on behind into Scotland towards the end of the run as colder air digs southwards however But, little point in worrying about such detail in a day 10 chart. Overall trends this evening are certainly encouraging!

These charts change as often as the op but that's an impressive -NAO signature from the Trop all the way up into the strat!!

The GEM is absolutely stunning, best of the 12z runs so far!

The ECM only just has snow making it into Scotland by 240 so while the overall pattern is impressive, it doesn't quite go out far enough for the UK to see the benefits The EC clusters though are fantastic, just about all of them showing some form of block

They’re not the worst i’ve ever seen..

Came here to say this too. I think they were talking specifically about a technical SSW, i.e full zonal reversal. 3 GEFS members are going for that which they mentioned. So the GEFS isn’t really “going for it” either at this stage & they didn’t really go into detail about exactly what GLOSEA was showing.

I would absolutely love to, unfortunately the only website on the entire internet that hosts GSDM/AAM/GWO charts has decided to password protect it and be incredibly selective to who he allows access.

Indeed. Impressively high Wave 1 amplitude being predicted by the GFS as the month comes to a close just as wave 2 beings to subside. Continued pressure on the strat vortex is what we want to see!

I think it's probably different with each SSW and depends on the type/area of the trigger and whether it's a top down warming or bottom up warning I would presume

There was a study in 2016 (can't remember for the life of me who by otherwise I'd link it, maybe someone can post it) that showed the UK/NW Europe was often colder prior to the SSW because the trop pattern which triggered an SSW was more favourable for UK/NW Europe cold than the pattern once the SSW had shaken things up. Zonal flow often increases because pressure against one side of the vortex tightens the pressure gradient, Recretos' post above makes for great reading.

Now we have the ECM seasonal on board with a significant weakening event my confidence is growing for January/February. Perhaps no real sign of an SSW just yet but we don't necessarily need one if we've got a weak enough vortex anyway. The GEFS are still going for a significant weakening, not a million miles away from a reversal though not quite there yert Worth noting the GFS Op isn't at all interested and departs massively from it's ensembles & ensemble mean, the higher resolution could be picking up on something that the ensembles aren't so it can't really be discounted at this stage, it's been fairly consistent with that signalling. Perhaps *some* signs of a coupling between Trop/Strat towards the end of the month but as these charts are based on GFS Op data, the usual caveats apply, we've seen a forecast coupling a couple of times this season only for it to be completely dropped on the next update

Not really - It's a three month anomaly chart so can't gleam much detail from it really. We could have an incredibly wet December and then have high pressure sat just to the south of the UK Jan/Feb and still get the chart above.

The new and updated GLOSEA makes for grim viewing.

Worth noting the +NAO pattern has been pushed back to the end of week 1/beginning of week 2 of December on the latest EC Weekly, previously it was +NAO from the beginning of week one, so a small subtle positive.

On behalf of everyone. What?

High pressure is too far north and as a result the UK sits right in the low pressure track area. Low after low bringing further rainfall to areas that are already struggling with flooding..

Things are moving in the right direction as far as I'm concerned. The Strat/Trop disconnect looks likely to last into at least early December with no sign of a coupling on any model anywhere. The forecast reduction in zonal winds at 10hPa will only serve to help things along should a coupling eventually happen. GEFS does tend to overestimate at times but always good to see a couple of members reaching down for a reversal, though I suspect these are a little premature, late December/first week of January is probably where we want to be looking for a potential SSW. Until then it looks like we'll be going into below average territory & with a continued disconnect I'd expect the "blocky" outputs to continue showing up on NWP outputs. November looks likely to come out below average which flies directly in the face of the seasonal models so little point worrying what they're showing 1-2 months down the line if they can't even get the current month right. Below average November. Continued Strat disconnect, possible SSW/Reversal late Dec/Early Jan. Lots to be excited about! I'm starting to think we're less and less likely to see a +NAO December..

The 6z may not be as good from a UK point of view but there's still lots to be excited about. Huge Siberian High coupled with the Aleutian low is good for longer term prospects in getting Stratospheric vortex disruption, this has been a fairly consistent trend in the last week or so.

The continued & increasing disconnect between Strat/Trop is something I'm beginning to get a little excited about We should see Wave 2 attacks begin to ramp up in the next week or two and this subsequently will weaken the vortex from an almost record breaking strength at 10hPa down closer to average and perhaps beyond if GEFS/CFS data is to be believed.

Just to add to this - Another view of the disconnect can be seen on the AM charts from StratObserve Height is displayed along the Y Axis, dates along the X Axis. The oranges show the strat vortex is quite healthy swirling around at the top, however the negative anoms at the bottom of the chart show the stronger vortex hasn't been able to propagate down through the atmosphere to impact surface conditions yet. All the blocking we're seeing on the models at the moment is very much trop led. This "trop led" blocking can impact the upper stratosphere given right the right pattern, continued wave braking/ep flux combined with Alteruen low/Scandi High combination is probably the reason for the forecast in reduction of strat zonal winds through this month. (though, this doesn't mean much given they're almost record breakingly strong.. lets see how low they can get! Weaker the better) Green lines = GEFS Pink = CFS, note CFS members in agreement for a massive reduction though important to note the strong -VE bias this model has as lead time increases. I suspect this is the reason the November CFS seasonal is going insane with blocking come January (ties in with Catacols thoughts from earlier quite well, actually) Lots of interesting things happening at the moment! Maybe just this once.. they'll all come together to give us one hell of a winter.

Blocky and slidey

Extended EPS relax the blocking around the UK although perhaps still indicative of a NW>SE tracking jet, that's notable is the complete lack of a signal for the TPV to setup anywhere near Greenland