Uncertainty

Barely any model discussion on here tonight . Loads of climate discourse and very few charts. This thread is where you analyse and discuss the latest model output, not ruminate on the loss of another potential cold U.K. winter over a month before it’s even started. If I were wanting a real cold spell, not a weak chilly November Atlantic ridge that flatters to deceive but allows the SPV to ultimately dominate (Ala last year), I’d be looking for a Scandi (high) Greenland (low) dipole to disturb the strat and kick off the blocking that the seasonals have long suggested. A but like this then, late on the Gem ens… 2/3rds of eps members have a similar picture, but look more unsettled generally In the meantime (e.g the next 10-14 days) it will continue wet in the W and quite possibly nationwide should the low move closer. Should this pattern persist, sooner or later the SW winds will align and a very wet atmospheric river episode could occur, we have avoided one so far with the southerly nature to the flow. Longer term, it may be a 2009 redux, it may not. But don’t forget the purpose of this thread before you post.

Not off one run Don. But if there is to be major blocking in early December, not just a brief late Nov cold snap, then we’d expect the 46 to start firming up on that on Thursday/Monday. If it further weakens the -NAO then I’d be more concerned that the signal was erroneous.

Bit of a wobble to be honest Seb. Lots more +NAO in there now. Will be a tad concerned if this continues on Thursday. I’m not convinced this October pattern has been ideal for realising the dreams of the seasonals, quite the opposite in fact. Vortex mugging us off again. Game over it ain’t of course, but this cold late Nov / early Dec is on shaky ground.

Thanks for this pal, Intriguing that these analogues are matched up with the anomalies progged by the Asian seasonal models (JMA/BCC). I think many on here are rightly sceptical of anything cold coming off this or any other winter due to so few -NAO winter months since 2013. Though folks probably thought the same thing in 2008 and 1938 too. Nevertheless, most of the analogues and modelling I’ve seen does support the possibility of your analogue at least partially verifying. For coldies, That blasted SE euro high anomaly needs to do one though. Otherwise we could end up with a 2018/19 style anomaly with plenty of blocking but no real cold and snow. I think that’s more likely than a 19/20 style Pv of doom, at least till mid Jan. Personally I agree with @Singularity’s superb metswift analysis that mentions a 25% chance of very cold conditions. More than usual, but certainly not nailed on.

Could be a rogue op, but the latest ecm op has a stronger ridge early next week which keeps the troughs from phasing and has a completely different outcome for next weekend. 12z 192 0z 192 I often find the models struggle with these cut off lows and sometimes they fling them over / through the U.K. too easily. Let’s see how big a cluster goes with this outcome.

Seasonal models: We’re thinking it’s actually going to be blocked and even cold this winter… GLOSEA: Hold my beer

The Beijing Climate Centre, a model I have begun to take an interest in in recent years, has updated. NDJ Another model flipping to blocking from last months update This model did well predicting the blocked winter of 20/21 and correctly backed off the idea of major blocking last winter. The CMC seasonal has also updated, tricky to read this one as it has flipped from Atlantic / Icelandic ridging to Scandi blocking but the theme of blocking remains strongly. Evidence is certainly beginning to gather…

Even the cfs pitching in for December.

Hopefully he won’t mind me sharing this… Giacamo Masato over on Twitter has an experimental statistical model that did a really good job with the summer period and much of last winter (though i think it got burned with the December block fail fiasco as we all did). I rate it really highly. This was the summer prediction, 3 months out in late March. The idea of a dry July and generally positive NAO manifested pretty well. Fascinatingly, it, like the ecm, has consistently predicted a -NAO for the early winter period and the latest iteration continues the run with bitter bells on. Again this has been consistent for many months. Peitao pangs SST analogues also going for N blocking I have to say it I can’t remember in the last 7 or 8 years this amount of seasonal guidance pointing consistently towards northern blocking. As ever I’d like to see Glosea climb aboard and like cansips abandon the whole U.K. low idea and join the ranks of the ecm. There’s still so much that could go wrong (or right depending on your prefs and outlook) but interesting it is definitely getting…

Meteofrance going for more backloaded blocking , December looks flatter… Dec Jan Feb Bit better for coldies than last month’s update Last month DJF ECM getting quite consistent with its -NAO signal. That’s 3 updates in a row. Also, I’m not convinced the seasonals have got the SSTs sussed. The Atlantic doesn’t look much like this right now (warm s of Greenland not cold like below) and the Nina is trending east based or basin wide whereas this looks modoki Ecm SSTs both look almost inverse tripole Actual current sst’s Surely an east based Nina with no Atlantic cold blob would increase -nao odds? Anyway lots of models still to report in but all 3 so far have some level of blocking so the game remains afoot.

That’s nearly a b word (I’ve still never said it on the forum) as the cansips is normally very zonal for the midwinter months. I can’t remember it spewing something like that out on a relatively short lead time. Will wait till all the other October modelling out before putting out my winter musings. But for now I echo the ‘interesting now’ sentiment above!

You are using this one example of where the anomalies were wrong (which they of course will be, around a 1/4 of the time) to suddenly preach to the many members and readers of this forum that these anomalies (which are based around the best performing models on the planet and adjusted slightly on weekdays by skilled human forecasters) are ‘rarely right’ and ‘low value to the U.K.’ You then proceed to label them no better than a bluff which demeans the entire forecasting paradigm. This is slanderous and needs to be called out. You are doing this because you lost this argument with mushy ( and given the like ratios, the rest of the forum) over the summer. One ‘victory’ for the anti-anomaly worldview is not going to to change anything. What is more frustrating for me is that you do often make good observations and musings about the weather and the models and frequently (though not on the above occasion) back up your suppositions with charts and data. Please stick to doing this, rather that engaging in antagonistic one-upmanship. For example, you are absolutely right about the shift in the models to a period of them predicting blocking in the medium term and reality flattening things out in the shorter term. I, like you, can remember many, many periods where this has been the case (last Xmas the most raw and heartbreaking example for coldies) but there have been whole seasons where that phenomenon has persisted. BUT you cannot relate that directly to a failure of the anomaly charts. They are a best fit, drawn mostly from the ecm/gfs/gem and are prone to the same biases as the models that generate them. The question is, if not them, then what? I am, perhaps controversially to some members of this forum, open to clues vis the weather from a multitude of sources including solar, singularities, analogs even to observing nature and correlating natural signs with past weather events. So I am not a modelling ‘fanatic’. Nevertheless, the noaa anomalies remain, for many others and me, the best ‘starting point’ for predicting the weather in the medium term that we have. Finally, it being October and a bit zonal is neither surprising nor unexpected. You suggest this Atlantic phase could last till Christmas (3 months!) without providing any charts for that period or referencing any particular forecast. This will frighten many members. Today’s models finally look to be reacting to the movement of the mjo by indicating some Atlantic and then possibly Scandinavian blocking around day 8 Though as referenced above I am somewhat dubious about this and the potential for flattening nearer the time remains very strongly. But it does show a near 3 month Atlantic phase is not nailed on yet. Finally, It is La Niña again which tends to suggest Atlantic ridging especially in November, the cfs highlights this possibility.

There’s more momentum now in the idea that after next weekends low pressure traverses, high pressure could return (as it so often has recently). First of all the signal is there and consistent in the noaa anomalies The ECM op follows this neatly The GFS roots the heights slightly further south but the same general story being told. The GEM is flatter and a disturbance sneaks over the top at day 9. Though interestingly the heights still build eventually. This suggests to me there is something driving this pressure build that the models have cottoned on to… A look at the tropics suggests the mjo could be minded to head back to phases 4 and 5. Using the September phase 4 and October phase 5 Nina composites, we can see some similarities to the suggested progression. Obviously the high cyclone activity in the Atlantic complicates the above, particularly TS Ian which is eyeing up Florida as we speak. The JMA, for example, keeps the remnants of Ian languishing around the CONUS ( manifested here by the 1010mb low near the gulf). This means the extra amplification in the Atlantic never occurs and a flatter pattern results. it does build eventually by day 14, adding to the suggestion that some kind of hp build is highly likely but the timing is subject to change. Going back to the ecm day 9 chart, we can see the remnants of Ian amplifying the jet of the Eastern seaboard, adding to the meriodonality of the jet and increasing the waveheight of the U.K. ridge. So the next 3 stages of the forecast are: a) A colder period of northerly / NW winds until next weekend = almost certain b) A strong developing low impacting the U.K. next weekend = likely, but track very uncertain c) Suggestions of renewed ridging near the U.K. = possible, but still only a suggestion at present.

I’ll miss this La Niña when it’s gone! Mean temps still below average after day 10, according to the GEFS of course… This is turning out to be an ‘unusually normal’ September, with the unrelenting heat of recent months (and Septembers) notably absent. The continued attempts at ridging in the mid / N Atlantic are notable to this observer as signposts for the coming months as they reflect a) the continued Nina base state and b) the anomalous warm SSTs in the that same region. What’s also fascinating is the consistency of this signal in the medium range: check out the day 12 GEM mean Now compare that with the NAEFS If the EPS completes the set later on then we could end up a with a CET below 15 which would be Remarkable considering the warm and humid opening to the month.

Afternoon. Time for a round up of the short, medium and speculative longer term outlooks for the U.K. Monday First of all, it looks dry, cool and perhaps bright in future the SE for most on Monday, which given the circumstances, many will be grateful for on such a hugely important day. The cloudiness is never an easy call but again the SE looks likely to be bright with some sunny spells Later next week The models are still wrestling with the waveheight and subsequent durability of the toppling high that is presently dominating the weather. The models have been flirting with either breaking down quickly (e.g Tuesday) or by prolonging it and reinforcing it from the W. The 0z gfs tries this, with the ridge still firmly in place over the SE on Thursday And reinforces it with more HP over the weekend The ECM on the other hand has a weaker ridge on Thursday Leading to an alternative scenario where the next batch of Atlantic HP is sent N, forcing a deep trough over the UK ! The EPS mean suggests this is an extreme solution, but the notion of HP west and LP SE is a reasonable one NOAA is keen on this pattern too, albeit with less amplitude than the latest EPS Into October After the above the ec46 hints at a westerly flow for a time, but into mid October there are some early suggestions of higher pressure over Scandinavia I won’t go into the early winter stuff here, but there’s a nice buzz around the early winter thread for anyone who wants to hypothesise about the prospects this winter. It’s certainly looking intriguing, though broadly within the expected envelope for yet another Nina winter. Regards Josh

I see your CFS and I raise you a CMCC If Glosea goes blocked tomorrow then I’m going all in! @Don 5th of Jan 21 mate. It was a very drawn out affair that kept the winter blocked and kept things interesting but never really stepped into memorable winter mode.

The worst yet? I have to respectfully disagree with you there Dan. It’s a Nina with a strongly negative -IOD and, as you stated, no cold blob in the Atlantic that supercharged our dismal winters of the mid to late 2010s. The last two Nina’s were forecasted to be strong at this point and ended up moderate at best. Fair chance this one could end up moderate too, and way to early to say whether it’ll be modoki or east based. The Wqbo / strong solar combo is actually better for cold than EQBO / weak solar. IMHO 2019 at this stage was ‘the worst yet’ already nailed on wet and windy with the strong +IOD and the modelling was already very strongly favouring +NAO. clearly a cyclonic winter as shown by the latest cansips is in play but a 2015 / 2019 style +++NAO is NOT the form horse for me. Especially not Nov/Dec. There was quite a bit of blocking on the seasonals in the August update. Unless, as CC states it all evaporates, I will maintain my belief that a ‘colder’ winter is plausible.

After the party low leaves town, all the big 3 models all have high pressure building back strongly. At day 9… GEM ECM GFS So it’s a done deal, right? Not quite, take a peak at the icon 12z Here, the tropical feature, which is partly responsible for building the ridge on the 3 main models is closer to being absorbed by the long wave trough over the U.K. It’s not the favoured option on the GEFS, but this outlier member shows what could transpire at the extreme end. The latest NOAA chart has the high to the NW with scope for something to creep underneath Further on, the Ec46 has plenty of LP for Europe But HP has been so resilient during this lengthy La Niña spell, so I wouldn’t write it off from being more influential as September progresses.

Both the GEFS and EPS are keen to push the low over the UK, though the latter is a tad slower. However, the odd op run shows that the far west option is still plausible, the present iteration of the GEM is representative of this less likely option. The 0z Ec op was an extreme example, tonight’s keeps its west too but with fronts draped over many areas it would still be unsettled. Even the GEM solution has fronts encroaching to the SW so overall an unsettled switch by next weekend is favoured. The reason behind the uncertainty if the interaction between a low to the S and the trough dropping down from the NW. Both can be seen on the GFS with late Thursday / early Friday being the potential phasing timeframe. The precise mechanics of this phasing is unsurprisingly proving very challenging for the models. The envelope stretches from a hot and unstable plume to a dartboard low. Not an easy forecast.

Why do you think it’s going to fail? There is actually an unusual amount of evidence to suggest that the AH will in fact build strongly around day 9/10. The EC46 has been rock solid on this development, especially in the w.b 8th August: The long range models have generally been very keen on suggesting anomalous HP near the U.K. during August, here’s the Copernicus multi-model mean. The main Ops presently all agree on this pressure build from around day 9 or 10 GEM day 10 ECM GFS Beyond this, good ensemble support for the signal to persist for most of that week EPS 10th August GEPS GEFS Finally, just a hint appearing on the noaa charts. Expect this to be significantly stronger tonight. These are anomalously HP dominated charts especially for August but it must be said that last August had a lot of HP even if it was dull and 2020 had a memorable hot and thundery spell in the first half so this 3 year Nina has provided us with some high pressure in August. In terms of meteorological reasoning that this pressure build might ‘fail’ I do see that the signal for the mjo to enter the maritimes has weakened somewhat so that needs watching as the blocking could easily head NW, you can see on the GEPS anomalies that nudging the high a bit more NW would lead to a cooler cloudier spell Nevertheless, the signal for an anomalous high to build somewhere in our vicinity from around day 10 is very strong and consistent.

Hello all I don’t post in this thread often but severe weather is my thing and I haven’t seen so much as a strike in nearly two years in cloudy Cumbria. However… Tuesday afternoon has the potential to support a convective parameter space rarely seen in northern England / SW Scotland… Cape in the 2500+ range Off the charts on the GEM Plenty of DLS Height falls ahead of the approaching shortwave to the S DPs into the high 60s Fahrenheit Only time I have seen this anything akin to this before is the time @Ben Sainsbury was perhaps referring to which was this event in July 2019 We had two fast moving supercells that day in N England and Scotland. To me, hyperbole aside, this looks more vicious. Timing of the breakdown is still not quite nailed on so not calling it just yet, but a highly rare severe thunderstorm event is on the horizon as this quite remarkable spell of weather comes to an explosive end. If this is still the picture come late Saturday then all bets are off.

Looking beyond plumegate, a 3rd ridge noses in by day 10 on the ECM… GFS very similar Broadly supported by the GEFS The GEM, whilst introducing an unsettled north westerly for a time, also has evidence of this 3rd ridge to the SW So it’s quite possible we could have 3 bursts of high pressure, with the quasi-breakdown of the 2nd ridge later next weekend harbouring the greatest chance of a burst of very hot weather. Interestingly, the normally cautious Icon goes for big time heat and an incoming thundery low by the end of its run. Lots of moving parts then still and uncertainty remains but little rain for S areas looks highly likely and the spectre of severe heat remains possible next weekend.

The two statements you make do not follow on from one another. Why would a brief Atlantic incursion in the NW preclude the temperature you have selected from verifying later in the forecast period, especially in the S? Your reading of the present modelling is that 35+ is now off the cards? ECM op GFS control JMA UKMO 168 is headed that way You don’t even need the big plume for 35c in the south. That HP sticking around for a few days in mid July and some subsiding air will suffice. The plumes suggested above and consistently over the past few days suggest that record temperatures are possible. Longer range modelling including the EC46 are indicating above average temps will be possible well into August. The latest GEFS for day 10 has an anomaly almost tailor made for heatwave conditions. Yet your brief summation, devoid of evidential underpinning, would suggest to our thousands of readers that such a threat has now receded. Weather forecasting is deeply nuanced and even nailed on ‘spells’ of extreme weather sometimes vanish or collapse within 72 hours. There is no convincing evidence for the U.K. record to fall at present but my use of the word ‘possible’ earlier reflected the fact that the parameter space of the present pattern in the euro - Atl sector and evolving climactic changes do allow for such a possibility to actualise. Regardless, 35 degrees in SE England in July is neither extreme nor unusual. On the basis of current modelling I’d say it’s probably likely over the coming weeks.

The next frame, although we shall never know, might have been quite remarkable…

This summer is looking quite troubling heat wise for most of europe. Such a striking, and consistent, signal for persistent high temps on the 46 W2 W3 W4 W5 As James has pointed out, in the medium term, a pattern at least conducive to a very hot spell of weather for England looks plausible late next week. Some of those wacky gfs runs were a bit extreme, but they do highlight the possibility space we are now entering. And if the 46 is onto something, such chances will remain possible further down the line this summer. This is a La Niña summer after all, something to ponder… As for those suggestions of a washout in western ‘England’, the present forecasts don’t support such an outcome. Western Scotland perhaps…