Model output discussion - summer rolls on

[Iceaxecrampon]

Eyes down  - here we go.

(Banter? - maybe - but the topics gone)

[Frosty.]

Dream synoptics in winter from the Gfs 6z operational and even in mid / late september this would feel wintry straight from the Arctic.. a wishbone effect too!❄❄❄

[Frosty.]

Looking at the GEFS 6z mean the rule of thumb is that the driest, brightest and warmest weather later this weekend and throughout next week would be further south / southeast with the most changeable and cooler conditions further north / northwest..Beyond that there are indications that high pressure could build in nationwide with a pleasant spell with warm sunny periods but chilly nights under clear skies with patchy mist / fog forming..nice mellow autumn weather in other words.☺

[stodge]

Afternoon all

Completely FI and probably completely unsupported but:

This would probably bring the colour back to your cheeks !!

Chilly spell following:

It won't happen though.

[Tamara]

17 hours ago, Singularity said:

Much like with the second half of August, there's a nasty sense that something's just not quite right with the weather patterns. 

Currently, I can see AAM projected to rise, with the GWO getting moving through phase 5 in the coming week, and there is some eastern Pacific to tropical Atlantic MJO activity being indicated, but the model trends for next week are taking the historical precedent for the atmospheric response to such developments and, er, plopping on them.

An increasingly vigorous Atlantic jet, flattening ridges as they attempt to build across the UK and NW Europe, is the opposite to the usual response. For a possible cause, I am tempted to simply look to the big uptick in Atlantic basin tropical-extratropical cyclone movement, but this is not a clear solution; while this can increase the thermal gradient and boost the jet stream, it can also supply large amounts of anomalously warm air aloft that then sinks down at the mid-high latitudes and lead to unusually strong ridges that can move across the UK. The ECM 12z of yesterday showed such an outcome at the end of its range.

GFS 12z of today does also feature such an eventuality following a brief exploration of the flatter jet outcome, but with the ridge out west of the UK - hence the unseasonably cool (if, IMO, overly dramatic) day 10-16 output from that run. 

In that we see the nature of these tropical-extratropical cyclone movements. They can abruptly change our weather in a wide variety of ways, and potentially for quite some time (ex-Bertha, 2014, had impacts that kept August of that year cool and often showery for several weeks).

 

That being said, unless the modelling of an emerging El Nino and appropriate atmospheric response turns out to be a total misfire - which is sadly not out of the question - then there ought to be some fight back of the weather patterns against flattening ridges and driving cool air into NW Europe via the UK. I suppose we'll soon see one way or the other! Can't say I'm enjoying 2018 much these days though, to be frank it's being a right twit .

Yes I stated the other day that August had featured a cancelling out process of the tropics vs the extra tropics, but one that still appeared to be cuing up very nicely for the re-start of the next atmospheric circulation to resume the progress up to late July. Which up till then had beautifully read the script and meant that not just was the weather itself lovely to savour, but also there was satisfaction in seeing the difficult processes and explanations play out and provide personal happiness and enjoyment of attempting to oversee developments as well.   

Humility is indeed a vital quality, and one of the first we should all should try to eschew - but on the other hand no-one earns a salary to take time out to post on this thread and on that basis it should be a personally enjoyable and rewarding experience at the same time as one shouldn't be beholden to expectations of total clairvoyency in terms of suggestions made ahead as to how the patterns may evolve.

On that basis maybe not too many apologies should be issued for not reading the weather patterns correct 100% of the time should be made - the likes of the METO as a professional institution would not provide a service at all if they had to issue apologies and explanations for every time Mother Nature didn't follow the best measured expectations. Additionally, the complexities of the atmosphere defeating human attempts to study them, does not justify those minorities who always seem to appear at these times to suggest the 'teleconnections don't work'. They almost certainly do work - its just the hardest task to try and understand them, relay and explain them - and those that don't try but criticise first and foremost instead - should practice their own humility first

Such sentiments of humility within these contexts become even more important as the audience no doubt starts increasing and changes ahead of yet another autumn>winter chase for cold patterns. Its my experience that whilst most on this thread, and large parts of the site as a whole, consider the busy season the most exciting and absorbing, it is also the time that unfortunately humility is usually least evident.

With all the above in mind, this is the last post on this thread of the sequence of summaries since May covering this wonderful summer season just ended ( a small few at least will no doubt be relieved and delighted to see the back of the never ending length posts) and it has been a wonderful summer despite the relative disappointments of August and the now apparent stuttering of developments for any further sustained warm and settled conditions in this month also.

The starting point of discussion far back in May was whether the step change to a contrasting much warmer second half of the Spring from the first half would successfully negotiate the hurdles of previous years where warm late Springs have only led on to a downward path to cool and more unsettled conditions.

The pros and cons revolved around stubborn persistence of La Nina type circulation lag set against the suggestion of gradual changes to more Nino-ish patterns in later summer>autumn and hence trying to 'risk assess' mid Atlantic ridge propensity for preventing warm air advection building sustainably (and more especially from the south)

or, 

whether a greater eastward extension of ridging would prevent this happening (again) and instead , over time, encourage development towards trough activity to our west in the Atlantic and further assist plume like activity from a southerly vector to take over from the Azores High.

As it turned out the ocean signal indeed continued to build towards an El Nino standing wave, whilst the atmosphere in terms of the extra tropics rather lagged the vestiges of the La Nina regime with low angular momentum and easterly trade wind patterns evident during June. The Atlantic pattern in the first half of summer was in many ways was not too dissimilar to a traditional La Nina summer pattern with the core heights centred around an intense sub tropical Azores ridge,and one which occasionally waxes but mostly retracts westwards due to the effect of upstream amplification c/o easterly trade wind domination in the Pacific

However, this time around, the the unusually north and eastwards displacement of these core Azores/Atlantic ridging heights means that the downstream trough that is usually reserved for the UK and NW Europe was erased quite some distance towards NW parts of Russia  So instead of customary low pressure upper cold pool - to the much greater extent and by way of total contrast, home grown heat build in situ from these ridges with the NW of the UK first to benefit from this.

As the summer progressed, and as the Pacific pattern started to couple the atmosphere towards the steadily warming ocean signal, the pattern did indeed start to signal a gradual transfer of core heights NE - culminating in (what turned out to be) the one and only real plume scenario of the whole summer in late July with the much anticipated and discussed Scandinavian heights and Atlantic trough. 

More of these plume scenarios into late summer and early autumn were envisaged and commented on several times.This late July Pacific forcing passage has however unexpectedly proved to a brief culmination of steady development since Spring

 What was subsequently envisaged some four weeks back was a res-set of the late July pattern through the middle part of August to repeat the sequence during the last third/last week of August. As we know, and as has been reasoned and explained, this sequence was delayed and August turned out to be more changeable and cooler for longer than seemed likely.

So to September, and the modelling expectations of upturn once more in angular momentum remain present, but seem to keep remaining in real time at the end of arms reach.  This not just applying to the CFS and its well know biases (those starting to re-appear here for winter attendance should beware its tropospheric>stratospheric modelling) but the ECM is also proving culpable to its own biases much as the GFS with its own -ve tropical biases.

 

*So famous last words of hers when she said that seasonal modelling of AAM had been proving reliable* Ha-ha!

Another example of freely given humility..

Extrapolations of re-engagement of the Pacific standing wave have stayed around the equivalent of chasing optimum synoptics at day 10 with NWP.

Instead we see a return to Western Hemisphere engagement of VP200 tropical convection anomaly at the expense of the Pacific.

 

This renders suggestion of recently rather void that the opposite seemed likely to prevail in the Pacific instead. 

At the same time no surprise the African wave signifies greater hurricane activity transferred from the Pacific back to the tropical Atlantic. An echo closer to September 2017, and against wider earlier expectations for September 2018

The greater -ve tendency in the atmospheric circulation sees transfer into -ve Asian mountain torque tendency in the extra tropics

This is the signal to amplify the Pacific profile through deceleration of the Jetstream there, and downstream retracts the sub tropical ridging in the Atlantic. This ends the recent attempts for Scandinavian heights to prevail along with the suggested longer settled spell some days back and also means that the attempted re-set of the ridge from the SW is more supressed from the weekend allowing the jet further south and greater trough intervention

It had been envisaged the GWO might hold ground in weak signal and then resume progress to higher AAM orbit sooner. However, eventual capitulation in the extra tropics (as discussed above) has been sufficient to re-engage the Global Wind Oscillation and end the long period of resistance in weak and incoherent orbit with a move into low angular momentum Phase 1.

This definitely precludes any immediate re-positioning close to the opposite end of the spectrum in El Nino Phase 5 (as briefly achieved in late July at 'peak' of the Nino standing wave development). Its now about revising expectations in relation to how the eventual natural upswing in the tropical>extra tropical pattern can recover angular momentum back to a lower amplitude Phase 4  This reduced orbit expectation wavelength is indicative of the faltering of development of the progress to the expectations of weak El Nino through this autumn and then into winter.

Its not a preference of mine at all, but not a surprise either in the 10 day period to see the models move away from warmer and more settled solutions as the re-engagement of higher angular momentum tendency keeps being put back in time. Instead the mid Atlantic ridge is being programmed in most modelling at the moment to engage a greater balance of polar maritime air, keep the jet stream straddling close to the UK and prevent it lifting further north and allowing sub tropical warmth to approach from the south and build back an Indian Summer.

This said, the GEM has been suggesting that some cut off may occur in the jet stream to our west and provide a break on advancement of the migrating Atlantic ridge and a loop of the jet to our S and SW to engage something of a plume scenario through next week. This is not an uncommon scenario based on past similar situations, and would be lovely to see emerge - though at present it remains a low chance probability. 

Something will give with this situation at some stage, as natural tropical.. extra tropical cycles dictate but essentially the low frequency signal in the Pacific has gone more AWOL since August at precisely the time that it was set not just to allow August to repeat the feats of 1976 and 1995 - but quite conceivably surpass them with a marvellous September as well.

'What ifs' and 'could have been' aside, its still been a fantastic summer and thanks should go to the regular contributors on this thread who have taken time to provide model sum ups and also enjoy the positivity of the weather suggested by them, at least until relatively recently taking the season as a whole.

A long way it seems from now until next summer, but time never stands still

 

 

[Frosty.]

It's worth noting that the GEFS 6z also shows some very warm anticyclonic options in the extended range..the cold Northerly on the 6z operational isn't supported but I won't lose any sleep about that, a cold Northerly in mid / late sept is a waste of time!

[Man With Beard]

UKMO 12Z: This wouldn't be a bad outcome for England / Wales

Potentially very warm and sunny in the south (i.e. 26C plus) , if Atlantic cloud can be avoided. 

Edited September 5, 2018 by Man With Beard

[feb1991blizzard]

Not a million miles away from dragging down a Northerly on the GFS 12z.

[Frosty.]

The Gem 12z shows high pressure becoming increasingly influential, initially across the south and then nationwide with plenty of fine pleasantly warm days further south but also some chilly nights.. But then a much warmer continental inflow towards the end of the run.☺

[damianslaw]

Models showing a very changeable outlook, and gone are the suggestions of predominantly fine settled conditions. In the short -term quite a complicated scenario, cyclonic conditions, cool with outbreaks of showery rain, sometimes heavy, and frontal activity causing a bit of a headache for forecasters - difficult to pin point when and where and heavy precipitation will be.

Into next week - a flat fired up jet forecast to make a beeline for the UK, and a fine margin between polar maritime air, returning polar maritime air and tropical maritime air invading. Odds favour more of a polar flavour to things, so temps quite close to average, perhaps some ridge development to the south bringing some chilly nights as well, however, we have a fly in the ointment and that is tropical storm activity - which will continue to mix things up, and allow for sudden short-term developments - every chance could amplify the flow, ridge development could shoot north through mid atlantic and a downstream trough and north westerly even northerly flow could then descend.

Also lurking to the NE is the building of heights, slow moving trough overhead and cyclonic conditions could be the form horse.. 

All very messy, all very uncertain.

[Man With Beard]

This morning's ECM looking hot for a time next week in England. Raw data going for 28C next Wednesday (26C quite widely) . Will that be close to the mark? 

[Frosty.]

1 hour ago, Man With Beard said:

This morning's ECM looking hot for a time next week in England. Raw data going for 28C next Wednesday (26C quite widely) . Will that be close to the mark? 

Indeed, certainly the Ecm 00z shows some heat potential for a time next week across england and wales, especially further s / se.☺

Edited September 6, 2018 by Frosty.

[Man With Beard]

A couple of observations from this morning's clusters D10-15. First, height anomalies returning to Europe on many runs, and slightly raised into the UK - this should mean the UK stays in a milder SW flow. Second, those lines to the NW get ever tighter as we move D15 - this could mean stormy conditions not far from the NW. 

We're talking 2 weeks out though so plenty of time for change. 

 

 

[Frosty.]

The Gfs 6z operational certainly shows some hot summery plumey weather later in the run..really impressive charts for the time of year.☺

[Singularity]

Hmm. Hints that maybe hurricane Florence could trigger upstream amplification soon enough that the main Atlantic trough stalls far west enough for some European ridge action. Should the trough then drop south as amplification increases further, well, the GFS 06z shows perhaps the most extreme result .

Trouble is, it's possible that Florence could avoid the recurving path and nullify those downstream impacts on our weather, though the latest modelling does favour that strongly, even if it hits the US, as a 'scraping' impact is being indicated; crossing the Carolinas or thereabouts in an arc before exiting to the ENE or NE.

The late stages of the GFS 06z run are why I'm glad it still goes out past +10 days despite the poor reliability .

[Frosty.]

The Gfs 12z operational appears to have got stuck on T+348 hours for the last 10 mins..nice chart though..it probably didn't want to load T+372 and I can see why!

Edited September 6, 2018 by Frosty.

[Frosty.]

The Ecm 12z is going for a potentially very warm / hot spell next week..temps would be well above average for the time of year across england and wales depending on sunshine amounts being good the temps would be into the mid / high 20's celsius further s / se!.☺..considering the average for the SE is now 19c 66f...could be much higher than that!

Edited September 6, 2018 by Frosty.

[Man With Beard]

Yes Frosty, 25/26C from Tuesday to Thursday on the ECM raw data, and still 23C by 15th.

It does look like one of those patterns that could easily get squashed by the Atlantic jet (as the UKMO and GFS do), but a similar situation just a couple of weeks ago in August held through to T0, so some reason to think the ECM op might be worth a bet. 

[Mike Poole]

Well the day 10 charts from the 12s just highlight the amount of uncertainty, here's ECM, GEM, GFS and FV3:

All over the place, over most of the summer the evolution has been slow reflecting anticyclonic influence, so the model output at this range was credible, now it isn't.  In the reliable, ECM at T120:

I'll take that in the south.

Edited September 6, 2018 by Mike Poole

[Froze were the Days]

So what ever happened to the cool westerly Pm air stream that was forecast for more than a few ECM runs in approximately 5/6 days time and lasting to the end of the run?...disappeared that's what, and all we have now is the dratted heights to the south (which never seem far away) continuing the warmth in at least the south...when will this hell end and some proper cool air get mixed into the continent?

[I remember Atlantic 252]

2 minutes ago, Froze were the Days said:

So what ever happened to the cool westerly Pm air stream that was forecast for more than a few ECM runs in approximately 5/6 days time and lasting to the end of the run?...disappeared that's what, and all we have now is the dratted heights to the south (which never seem far away) continuing the warmth in at least the south...when will this hell end and some proper cool air get mixed into the continent?

good, got 4-5 months for that trash, let's have a bit more summer!

models all over the place anyway, could be anything in FI

[mb018538]

Early September is still as good as summer across Iberia/balkans etc, temps easily over 30c in numerous spots. It’ll take until october before it really cools off.

[Mike Poole]

Actually, after all the uncertainty of the past few days, ECM 12z ensemble mean looks pretty good for settled and warm weather at least for the south.  Here T240:

 

 

[stainesbloke]

1 hour ago, Froze were the Days said:

So what ever happened to the cool westerly Pm air stream that was forecast for more than a few ECM runs in approximately 5/6 days time and lasting to the end of the run?...disappeared that's what, and all we have now is the dratted heights to the south (which never seem far away) continuing the warmth in at least the south...when will this hell end and some proper cool air get mixed into the continent?

Patience. Since when has September been a cold month? It’s usually far better than August! By November it’ll have cooled down drastically and that will be the case for a good 4-5 months.

[Froze were the Days]

52 minutes ago, stainesbloke said:

Patience. Since when has September been a cold month? It’s usually far better than August! By November it’ll have cooled down drastically and that will be the case for a good 4-5 months.

Well it's been better then August in recent years and in my mind September is partly 'late summer' but after months of warm anomalies (August less so) a change wouldn't be a bad thing. Also in my mind with the affects of Global Warming there looks like plenty more years ahead with ever growing heat...some cool dry weather in the next month or so will do me a treat.

Very warm SST's and a warm continent I can't see anything cold or even cool on the agenda in the foreseeable sadly.