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


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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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3 minutes ago, stodge said:

Evening all 🙂

I confess I'm NOT looking forward to the next few days of heat down here in lowland East London. I am hoping the Estuary will provide a little cooling breeze which means the east of the capital is usually a degree or so cooler than the west in scenarios like this.

Tomorrow looks like being the hottest day and values of 35-37c are being widely forecast for London. Will it be hotter than last Friday? Given we are almost exactly seventeen years on from the 2003 heatwave, a value of 38c can't be ruled out and if the record went tomorrow I wouldn't be surprised though having three of the four hottest days on record within a 14 month period should be of note.

:Looking a little further on into early next week and our old mate Arpege keeps the oven full on for Monday:

arpegeuk-41-98-0.png?06-18arpegeuk-2-96-0.png?06-18arpegeuk-19-96-0.png?06-18

That suggests to this observer a less than cloudless aspect but perhaps not. Humidity is surprisingly low and I do know that when we get LP over Iberia it doesn't stop the skies being clear and the sun shining strongly and maybe this is the same so colour me confused.

GFS is much less keen on Monday heat:

96-778UK.GIF?06-1296-21UK.GIF?06-1296-600UK.GIF?06-12

I have to say I'm none the wiser - lowish humidity with lowish pressure.  No one seems to be ruling out a shower or a thunderstorm whether home-grown or imported. 

Maybe the Humidity Index is more indicative of how unpleasant it's going to be in my part of the world.

iconeu_uk1-47-96-0.png?06-17arpege-47-96-0.png?06-17

To cap it all, we're going for a roast lunch on Saturday - mad dogs and Englishmen as they say....

More like a roasting lunch! 😂

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1 hour ago, cheese said:

It didn’t, but we still exceeded 30C five times that month in Leeds. Including 5 consecutive days above 30C starting in late July. Chances are we won’t exceed 30C at all this month, let alone 5 days on the trot.

So yeah, Damien is right - this isn’t looking like a classic national heatwave. I’m sure records will fall somewhere but I think August 1995 is more than safe for now. I’d be surprised if even 1997 was threatened.

Nor is it looking like a repeat of  Aug 2003 which brought widespread consecutive days nationwide 30 degrees plus. 

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Evening All.A hot few days in the souff east a very warm week next week with increasingly thundery downpours. Anyone thinking this is not normal let's go back to 1984. Many many weeks of above average temperatures and low rainfall. Historical Weather is what I deal with , so anybody having a question please let me know! 

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2 minutes ago, ANYWEATHER said:

Evening All.A hot few days in the souff east a very warm week next week with increasingly thundery downpours. Anyone thinking this is not normal let's go back to 1984. Many many weeks of above average temperatures and low rainfall. 

The 2nd half of August 1984 was surprisingly hot.

However lets take the temperatures in London since thats within the area that the heatwave will really hit hard:

August 1984 had 5 days above 27c in London (and only 0.5mm of rain, so dry for sure!)

The forecast is for London to have 5 days above 32c...in a row...and quite possibly end up with nearly 5 days above 35c!

They are worlds apart at least in terms of heat intensity.

Really, the only comparisons that compare for the this upcoming 7 day period in terms of peak heat intensity is probably August 1911, June/July of 1976, maybe August 1990, August 2003 and maybe July 2006.

I

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We now have 28°C showing at midnight tomorrow night on the UKV

image.thumb.png.dd7d2abf1f0d3f31c39f0521b6c9b89c.png

Followed by this for Saturday afternoon

image.thumb.png.1cd65ae0e5c3164069cef4c9ca7e36d0.png

 

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8 minutes ago, matt111 said:

We now have 28°C showing at midnight tomorrow night on the UKV

image.thumb.png.dd7d2abf1f0d3f31c39f0521b6c9b89c.png

Followed by this for Saturday afternoon

image.thumb.png.1cd65ae0e5c3164069cef4c9ca7e36d0.png

 

These warm temps for tomorrow night seem to be gettin warmer and creeping further north and west into the midlands!!also yesterdays run for the same time was showing 23 degrees for a lot of england but is now showing 27 to 28 degrees widely across england up to leeds!!upgrades keep flooding in!!

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16 minutes ago, matt111 said:

We now have 28°C showing at midnight tomorrow night on the UKV

image.thumb.png.dd7d2abf1f0d3f31c39f0521b6c9b89c.png

Followed by this for Saturday afternoon

image.thumb.png.1cd65ae0e5c3164069cef4c9ca7e36d0.png

 

Looks like the record for highest overnight minima will be certainly threatened, moreso if you're 'lucky' enough to get stuck under cloud that'll hold in the heat in the night.

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24 minutes ago, matt111 said:

We now have 28°C showing at midnight tomorrow night on the UKV

image.thumb.png.dd7d2abf1f0d3f31c39f0521b6c9b89c.png

Followed by this for Saturday afternoon

image.thumb.png.1cd65ae0e5c3164069cef4c9ca7e36d0.png

 

Ah yes, I see a nice bracing 18°C max in Rhyl, pleasant for some! ;)

Edited by DaveL
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5 minutes ago, CheesepuffScott said:

Looks like the record for highest overnight minima will be certainly threatened, moreso if you're 'lucky' enough to get stuck under cloud that'll hold in the heat in the night.

Could well do with that. Looking at that whole run for tomorrow night, while it does show it dropping a bit further later in the night, some places don't drop any lower than 25°C. 

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Several posts moved over to the moans/banter/chat thread.

I appreciate that it may be exciting for some, and also horrible for some, but please try to stick to discussing the models. Posting MetOffice weather app data, or just general chit-chat should go in the appropriate thread as not to clog this one up.

Cheers.  🙂

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This sustained heat is going to be trouble for a number of people with resputaory problems including myself, stay safe everyone and hopefully we'll get some decent storms next week to cool things off. 

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A bunch of posts have been removed, please don't respond to posts which are clearly made to get a reaction.

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Ec has a flatter Atlantic jet than last run which pushes everything through that but quicker later next week ..... probably more likely on balance than the stagnant picture sustaining but still days 6-8 remain v uncertain re the progression of the pattern 

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Ukmo run looks very hot and slack flow se flow Tuesday Wednesday 

Edited by clark3r
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Quite unstable on the ECM for Tuesday and Wednesday (and some areas Monday). Looking very tropical in nature with high heat still (the convection does limit maxes somewhat though still hot, with the usual under-estimation your easily into the 30s every day) and probably decent risk of thunderstorms, especially over places like the Midlands where the cap will be that bit weaker already due to being on the edge of the plume.

Models again also suggest the development of thermal lows in our neck of the woods, again something typically seen somewhat further south in latitude! 

PS- also just worth mentioning that several of the high resolution models have somewhat backed off the extreme heat today. May not mean much as these models have been wrong at this range before, but they are broadly coming in 1-2c cooler than yesterdays runs for both today and tomorrow. Something to note.

Edited by kold weather
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Could be the hottest 5 days on record by an absolute mile of this happens. 36c plus for 5 days straight is mind blowing really.

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1 minute ago, mb018538 said:

Could be the hottest 5 days on record by an absolute mile of this happens. 36c plus for 5 days straight is mind blowing really.

Yes if it comes off that would be insane!

That being said the models have slighly edged downwards overnight on the heat, I suspect partly because they are looking increasingly convective from Sunday onwards as it comes closer towards the timeframe.

I still suspect somewhere is going to reach 32c every day until maybe Thursday as this point which would be a very impressive run of such high temperatures. However 5 days going 35C IMO is totally at the behest of there not being as much convection around as currently expected, which given the fairly low pressure and increasingly unstable airmass, looks a touch unlikely to me.

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A more zoomed in view of the UKV temperatures this pm, across the southern half of Britain. 

frizoom.png

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1 minute ago, Paul said:

A more zoomed in view of the UKV temperatures this pm, across the southern half of Britain. 

frizoom.png

Much like the other high resolution models, this too has also just shifted downwards a peg or two from the 35-36c range seen yesterday towards 34 with a localized 35c. 

Still exceptionally hot though across much of the SE, not often you get quite such a widespread area of 33-34c for several days forecast.

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A slightly cooler outlook on GFS this morning so less unpleasant. Whether this is a new trend after drifting towards a hotter outlook remains to be seen.

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Satellite imagery shows a lot of convective cloud to our south west, in fact I can already see it over west dorset bubbling away, all that cloud is moving pretty quickly and I can see the sun being gone from here by 10/11am. If LHR wants a run at 100f it’ll need to do it quickly as the cloud to the south west looks pretty dense.

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15 minutes ago, Alderc said:

Satellite imagery shows a lot of convective cloud to our south west, in fact I can already see it over west dorset bubbling away, all that cloud is moving pretty quickly and I can see the sun being gone from here by 10/11am. If LHR wants a run at 100f it’ll need to do it quickly as the cloud to the south west looks pretty dense.

Yes the AROME shows a line of convection slowly drifting NE, it looks a litlte more active on the fronts southern tail than was advertised yesterday which leads to a stronger chance of some convective action making it towards the SE by the close of plsy today, and indeed several models are kicking off showers even over the SE overnight.

How high Saturday goes probably largely depends on how much convective overhang there is and whether any more cells break out.

Mon-Weds now looking increasingly stormy and basically tropical in nature, with 30-33c in the SE and high chance of daily thunderstorms for just about all. Very impressive to see and going to be an amazing, if maybe unbearable at times and for some, period of time coming up.

Edited by kold weather
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Today's GFS 00Z looks to be a tad less hot than some previous runs; but, it is only one run, so the apparent cooling could well be down to inter-run NWP drift... but only time will answer that one?🤔

h500slp.png    h850t850eu.png

h500slp.png    h850t850eu.png

h500slp.png    h850t850eu.png

h500slp.png    h850t850eu.png

h500slp.png    h850t850eu.png

GEFS 00Z ens are nae bad, either: from an exceptional high of circa 19C, 850hPa temperatures (hardly surprisingly) sink back towards the mean::oldrolleyes:

t850Suffolk.png    prmslSuffolk.png

t2mSuffolk.png    prcpSuffolk.png

So, how does this heatwave compare to the much-vaunted 'classing heatwaves of yore'? Wee, perhaps the best answer to that one, is simply to remember that it hasn't happened yet! God, that was profound!:hi::oldgrin:

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