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Model output discussion - August hot spell - how hot, how long?


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Hmmm ukmo looks to keep it very warm throughout the run!!low is further west at 144 hours!!gfs seems an improvement early on as well!!are we about to see another extension to this warmth?ūüėĪ

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Astonishing rebound in momentum transport that is behind the current spectacular synoptics and associated high impact weather. Both the heat, and also the powder keg potential for thunderstorms.

*** USING THE ECM TO FORECAST TEMPERATURES IN A HEATWAVE - A REVIEW *** I often make predictions based on models several days ahead, and then I find it useful to revisit these predictions after t

The reality is that NWP is wholly congregated on, but susceptible to be blindsided and over preoccupied by, the re-ignition of the low frequency tropical convective standing wave across Africa and the

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To me it just looks like a continuation right into the weekend of heatwave conditions but its more focused overnight. Maybe down on daytime mid 30s but over night temps still look very warm with 19C in London and high teens elsewhere and with high humid levels still holding firm. Keep them fans and air cons running. 

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Well I‚Äôll take the Ukmo this evening , It is the summer holiday month after all . I hope the Ukmo is closer here and the ecm follows too soon . Gem and GFS are yuck ūü§Ę¬†. All charts 144 Hours¬†

88D2215B-14D1-4E5D-861E-3771FFD58DDB.png

CC587D0B-7BAB-4401-B7ED-B9F3C3A31DA3.gif

A4D676C7-B5C2-4C3D-BDD7-9F617F155111.png

Edited by Mark wheeler
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6 minutes ago, Dominic Carey said:

How is the ECM looking so far?

It looks closer to the ukmo than the gfs at least then i will be happy!!ecm looked the best of the top 3 this morning up to 144 hours in my opinion!!

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39 minutes ago, Tamara said:

 

Astonishing rebound in momentum transport that is behind the current spectacular synoptics and associated high impact weather. Both the heat, and also the powder keg potential for thunderstorms.

The GWO has smashed its way through the El Nino attractor phases through into a weak amplitude Phase 5, based on the two day two consolidated lag. A reversal of the standing wave pattern between June and July and a resounding blueprint for the anomalous European and Scandinavian ridging presently in evidence.

818750421_GWOheat.thumb.GIF.559a98a54fa6a54b9c52fb1b59e3c25b.GIF

 

 

With that switch in mind, NWP has been suggesting, up to now, a wholesale collapse and reversal back of the present regime during next week.  Times like this, ahead of a suggested vigorous pattern change, (or more accurately switch back to a previous pattern) require extra caution because while the atmosphere ""remembers" its previous behaviours, there is no linear one size fits all response from one season to another. Therefore expecting the same responses from the forcing within the tropics and extra tropics, season on season, is over simplistic and erroneous. Especially the size of the correction these models appear to have been predicting.

Personally, with all the above waffle in mind, I am watching the disruption of the upper trough next week and how that phases with the residual heat lows from the stagnant heat dome mass that will have sat there for an extraordinary amount of time by the end of the coming weekend. No surprise at all that the Met Office have issued so many thunderstorm warnings day on day and no surprise at all if these calculations of how the Atlantic troughing phases with this stagnant slack low pressure mass runs into some difficulties.  There have already been some incremental corrections westward with this process and there is time up to 7/8 days ahead for more of these

All in all, a lot to be decided and not take for granted, from my own point of view at least, whatever the present modelling may presently suggest, from the early - but more especially mid to latter part of next week.

Edit 6pm

This was written earlier this afternoon until home commitments took over. Irrespective of the details (which are irrelevant in the circumstances at this distance in terms of what each model goes on show thereafter), the trend indeed continues further on latest 12z suite, so far, to take the main trough ever west of the UK in the middle of next week.  This is one such example of not taking each and every NWP operational and indeed ensemble data at face value but treat them as a snapshot in time and watch instead how they trend over a day or preferably two at a time

Should probably pin this as a rider to every post...signals lead models, models do not lead signals.

 

 

Brilliant input as ever Tamara. Thanks.

 

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Evening all ūüôā

Another day (the sixth in succession) above 30c in downtown East Ham - we reached 33c early afternoon but a more pronounced E'ly wind sprung up and it's starting to feel fractionally more comfortable. 

Thought I'd see where Arpege is taking us and it's very interesting:

arpegeuk-41-27-0.png?12-17arpegeuk-41-51-0.png?12-18arpegeuk-41-75-0.png?12-18arpegeuk-41-99-0.png?12-18

A last day of heat (30c?) tomorrow before a much cooler regime takes over for the south and east and the heat switches to the west and north on Friday and the north on Saturday.

The 500hpa synoptics are revealing:

arpegeuk-2-27-0.png?12-17arpegeuk-2-51-0.png?12-18arpegeuk-2-72-0.png?12-18

This isn't your normal end to a short-lived hot spell with a front coming in from the Atlantic and sweeping in fresher air from west to east.

In fact, this is the reverse - a complex trough to the south and east is introducing fresher air from the north east so the residual warmth gets pushed back west and north west while the cooler air takes over the east and south. Very unusual synoptics for the end of a prolonged hot spell.

Next week is all about what the Atlantic LP will do - fans of heat will be looking for it to stall out west - 12Z GFS OP didn't suggest that, perhaps the 12Z ECM will.

Edited by stodge
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8 minutes ago, mb018538 said:

Turns very unsettled, wet and windy a la GFS.

4CD6C84D-C428-4A3C-B58F-CE9E5759179A.thumb.png.4ac65dc93bdda07f0ff694193d4f475b.png

Yep it certainly does . I hope the Ukmo triumphs again .Ecm  Looks closer to the Gem to me  .

@Dominic Carey here are the charts from 144 hours .

BF643423-EFA1-43A4-9589-842BB747991A.gif

E6AF21DF-3922-40DB-9CAD-77007A43DF38.gif

2A4DB394-C7DC-4CE8-AAA0-EF8DFF2ED5C2.gif

C6EACB85-8E31-4E37-BDDF-3C169FE607C2.gif

516C92E1-A55D-41A9-95F8-AD9183E3650B.gif

Edited by Mark wheeler
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43 minutes ago, stodge said:

Evening all ūüôā

Another day (the sixth in succession) above 30c in downtown East Ham - we reached 33c early afternoon but a more pronounced E'ly wind sprung up and it's starting to feel fractionally more comfortable. 

Thought I'd see where Arpege is taking us and it's very interesting:

arpegeuk-41-27-0.png?12-17arpegeuk-41-51-0.png?12-18arpegeuk-41-75-0.png?12-18arpegeuk-41-99-0.png?12-18

A last day of heat (30c?) tomorrow before a much cooler regime takes over for the south and east and the heat switches to the west and north on Friday and the north on Saturday.

The 500hpa synoptics are revealing:

arpegeuk-2-27-0.png?12-17arpegeuk-2-51-0.png?12-18arpegeuk-2-72-0.png?12-18

This isn't your normal end to a short-lived hot spell with a front coming in from the Atlantic and sweeping in fresher air from west to east.

In fact, this is the reverse - a complex trough to the south and east is introducing fresher air from the north east so the residual warmth gets pushed back west and north west while the cooler air takes over the east and south. Very unusual synoptics for the end of a prolonged hot spell.

Next week is all about what the Atlantic LP will do - fans of heat will be looking for it to stall out west - 12Z GFS OP didn't suggest that, perhaps the 12Z ECM will.

Yes a very subtle difference in the feel of the air in this locale this evening. A change is afoot...

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6 minutes ago, Man With Beard said:

It will be interesting to follow the ECM mean over the next few runs, regarding the end of next week.

EDM1-192.GIF

This may look cut and dried, but analysing the individual ensembles, about 40% look like this, 30% are more progressive like the op run at T192 - however, the other 30% ish hold the trough far enough back to allow another plume into central/eastern areas - generally a 1 or 2 day affair, but a blast of heat all the same.

Bearing in mind @Tamara's post above, it will be interesting to see if this hotter cluster gains momentum in the next 24 hours.

Ukmo might be on to something here!!ecm looks good up to 144 hours!!the models already extended the warmth till early next week which is  a bonus as it is!to get extended further would be incredible!!

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8 minutes ago, sheikhy said:

Ukmo might be on to something here!!ecm looks good up to 144 hours!!the models already extended the warmth till early next week which is  a bonus as it is!to get extended further would be incredible!!

Ukmo has support from the mighty Navgem too this evening.

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53 minutes ago, johnholmes said:

Well the 2nd NOAA 6-10 keeps the same chart really from day 1. It remains very different from the previous outputs. One more and I'll have to start believing it is on to a marked change

https://www.cpc.ncep.noaa.gov/products/predictions/610day/500mb.php

 

this is one occassion i hope they are wrong!

 

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1 hour ago, Downpour said:

The air this evening (outside) is much more pleasant. Lovely to sit out in in fact. The soup of last night has gone.

Have you tried being inside? It’s worse tonight here in SE London... 25C, 70% humidity.... absolutely sweltering this will be my 4th tropical night! As for next week it certainly looks western areas are going to see some unsettled weather and blustery, probable we all get some wet weather but possibly an improvement by weekend.

6BC80762-4C9B-4A0B-8139-57FDFF8B4744.thumb.gif.e3fee3aafe4176551287af4dfff3d2a7.gif

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Gfs 18z moves towards ukmo at 120 and 144 hours!!also its all over the place for early morning thunderstorms tomorrow on the south east!!vastly different compared to 12z!!hard to believe the 18z when it could be wrong at just 12 hours!

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16 minutes ago, Daniel* said:

Have you tried being inside? It’s worse tonight here in SE London... 25C, 70% humidity.... absolutely sweltering this will be my 4th tropical night! As for next week it certainly looks western areas are going to see some unsettled weather and blustery, probable we all get some wet weather but possibly an improvement by weekend.

6BC80762-4C9B-4A0B-8139-57FDFF8B4744.thumb.gif.e3fee3aafe4176551287af4dfff3d2a7.gif

I made the mistake of venturing upstairs earlier. I’m now back in the garden genuinely contemplating sleeping in the shed. 

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Back to the ECM clusters then!

T144

ec-ens_nat_z500scenarios_2020081212_144.

It's obvious already that the progress of the Atlantic low is far from certain; cluster 1 (the UKMO option) does not have the trough close enough to affect the UK at this point, though it is outnumbered by more progressive clusters 2 and 3

T192

ec-ens_nat_z500scenarios_2020081212_192.

An interesting moment. It looks like the Atlantic low will sweep through, but in clusters 2 and 5, ridges to the east are putting up enough resistance to allow a quick plume (may not make it far up the country), while on cluster 4 the low has already gone. So quite a lot of uncertainty.

T240

ec-ens_nat_z500scenarios_2020081212_240.

The trough has broken into the UK fully on all clusters now - clusters 4 and 6 has progressed so quickly that a new area of heights follows, but these are small clusters in size.

T360

ec-ens_nat_z500scenarios_2020081212_360.

Too far out for detail, but the general signal is flat and less settled.

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