fergieweather

Little useful to add. Akin to the EC update of Monday, there's a signal in the latest run for strong mid-Atlantic ridging during 1st week of Nov, with resultant colder NW flow. This is also favoured in latest GloSea5. Both models suggest a blocked scenario most likely 1st half of Nov, albeit with uncertainty/spread in exactly how this manifests (respective H/L positioning). Either way, zonality looks less likely than average through first half of the month.

Yes, 00z EC ENS (15d meteograms) agree on a return to avg/slightly above avg TMax as next week progresses, followed by a bias slipping back to below avg into first few days of Nov.

Caution indeed, but not altogether surprising given signals (albeit presently not majority) in some extended M-R output from other centres. Glosea remains firm on early Nov blocking... BUT as I mentioned previously, we can't (yet) be clever re respective positions of high/low centres and resultant outcome re temperature regime here.

The latter scenario is favoured as warmth/copious moisture gets injected into the equation. Tomorrow's EC Monthly might be a bit more instructive (at least of sorts!) as it should have a better capture of the emergent situation in W Atlantic and downstream influences next week.

Much as we saw in the period prior to Nicole's extra-tropical transition, we've now entered another phase of model to-and-fro, courtesy of the incipient tropical storm development near Turks & Caicos. NHC gives this an 80% chance of this reaching tropical storm status over next 5 days, running northwards. Given resultant influence on jet strength, this situation has already shown over last 24hrs how models can start to swing towards an earlier return to mobility (versus previous output). In short, we are back in a situation where medium range confidence isn't at all great...!

I also subscribe to your opinion. It's all looking very interesting indeed. Compare & contrast to this time last year...!!

As you note, John, the ensemble spread post d6 is very marked (including in 00z EC). As I mentioned earlier, a key imponderable remains the position of high/low centres within a broadscale set-up of *some form* of blocking. I wouldn't want folk to assume blocking is a synonym for cold.

Re ECMWF 00z prognosis and this issue of favoured flow direction into extended medium range, below are the cropped-out 10-15d ENS wind roses for Reading. Note the predominance of NE'ly members, with a more equal split in clustering (ie incl those from SW) emerging towards/by end of run. Worth adding that against model climatology, TMax is signalled as average or slightly below throughout this period. Cheers.

Indeed. Very interesting times continue. Given ECMWF Monthly shifts the primary +ve MSLP anomaly to the NW of the UK for the 1st week of Nov, the implication would be to see colder conditions. GloSea5 also continues (as it has for some time) to run blocked into early Nov, albeit the exact scope and locations of associated high/low centres remains unclear, and thus our resultant weather type. GFS has been recently sniffing-out the sort of stratospheric signals (waning of zonal winds) previously suggested some weeks back by GloSea5 into Nov; however, that model indicates some *slight* reduction/weakening in blocked signature further into Nov and so confidence in outcome that far ahead is low. The overall UKMO view is for blocking/-ve NAO/-ve AO to dominate at least into early Nov (with temperatures thus perhaps below normal); a chance of this diminishing thereafter *but* for the risk of very mobile/stormy conditions to be nonetheless lower than average (that doesn't exclude the possibility!). As they also note, the interim period into late October - with LP to SW - may entrain phases of higher WBPT air for some areas, set against a keen SE/E flow. Nonetheless, a cold undercut means it'll certainly not be 'mild' in so far as sensible weather experienced by the masses...

Until we see how Nicole resolves, everything is viewed with caution into medium range.

Indeed. Interesting how this evening's ECMWF Monthly leans towards +ve heights establishing to N; a NE flow to close-out Oct, followed (albeit with an inevitably weakening signal) by something more northerly into 1st week of Nov, with 850hPa temp plumes gradually on a slide.

Ah, but still looks a pretty interesting winter period, for various reasons. Some key differences versus EC, but still quite distinct from the output we were looking at this time last year, for winter 15-16! November is always the more critical point when we expect (hope!) to see closer consensus between these models. Still a way to go before it's worthwhile hanging hat on any particular broad outcome for this winter.

GloSea5 was out today. Quite a different take on things...

Very interesting output, yes. But my firm advice would be to hold-off writing letters to Santa until we see the November EC output, plus wherever GloSea5 & MeteoFrance modelling leads us in the interim, be it consensual or not.

Indeed it did. Essentially it runs an consistent story through N-D-J-F of +ve GPH/MSLP anomalies to NW/N of UK; -ve ones to S/SW.

00z EC clusters generally lean similarly towards end of Oct (towards a resumption of mobility), much as GloSea5 has done for a while now. However, any such transition - whenever it materialises - will doubtless prove complex/messy. It'll thus be interesting to see if any further hint of blocking for November appears in tomorrow's EC Seasonal update, or whether it switches to something more mobile/zonal.

NB Signal for any early warming / reversal has waned recently. Next EC Seasonal output later this week may be instructive versus Glosea; ie if signs of -ve NAO into winter also turn less bullish versus last update.

An intriguing imponderable...!

Hiya This paper worth a read. Available online in full:

Relatively frequent, but any reversal of zonal winds associated with these (ie even temporarily) are rarities. There's a good case study & broader examination of these events in a paper online (I'd need to check the link/citation).

Don't get too hyperventilated. Very early days. Bear in mind the *majority* signal is for a zonal flow up aloft (& probably westerly QBO into winter, despite some nearer-term complexities in lower strat). Whilst key seasonal output (GloSea5, EC Seasonal & now MeteoFrance ARPEGE-climate too ) concur on the notion of a winter (at least *initially*) prone to blocking, there's members of eg GloSea5 being run daily, so much water has yet to pass under this particular bridge. Whilst 60 yrs of QBO data is hardly anything in the grander historical record, the fact remains that behaviour this year has been unprecedented within that 60-yr timeline. Thus, models may struggle to adequately synthesise what happens next on that front (& the strat generally), which needs to be factored-in despite other key teleconnections (eg as presently in Indian & Pacific Oceans) that may be bolstering the 'blocky' solutions for NW Europe shown in recent runs. *If* the output still paints same coherent story by mid-Nov, we might well be in business. The only certainty is that present strat diagnostics looking ahead to N-D-J-F bear little resemblance to those output at this time last year!

Sorry for delay. The answer I'm given is yes, in so far as the human input (ie expert examination of component signals from the model and pattern recognition).

A very good question. I will endeavour to source an answer for you.

Hi - sorry, to clarify. I'm talking about 10hPa, 60 deg. N model signal through November. An interesting possibility so early in the season, but not (currently) a majority ENS solution.

reversal at 10hPa, but signal very tentative at present.