The heatwave to end all heatwaves? Or a few nice days then a Northerly?

Whatever, it feels like it needs its own thread. 

As of this morning we have multiple runs hinting at temperatures at or above 40C by mid month. 

Today looks like the coolest day countrywide for 2 weeks at least. 

Gosh !

Check out the number of 850's between 20 and 25c ! 

https://www.wetterzentrale.de/en/show_diagrams.php?model=gfs&lid=ENS&var=2&bw=1&geoid=49909

As we now have a bespoke thread for this - Just thought I'd mention that on About Anglia last night they alluded to the fact that some forecast models had gone for 40C and 41C just recently.

They quickly added that they didn't think these would verify and that 30C was the highest we'd see.

However they went on to say that they're keeping a watch on things.

A 30C peak is every bit as outlierish in the other direction as a 40C peak. That's cool ramping.

This morning's GFS the op run, which peaks at just above 20C 850s, was if not a cool outlier then certainly at the cool end of the set. I think I counted fully 2 ensemble members that don't touch 15C 850s at some point in the run, and 15C means 32C.

Hot ensembles from the ECM.

GEFS similarly hot!

Recent heat records in dozens of countries.  Will the next fortnight be our turn.

Worth including French heatwave details in here given that's where we're importing the air from. And because it could be catastrophic. Here's last night's GFS 18z. Max temperature in the SW of 48C and widely 45-46C including, remarkably, on the Normandy coast.

You'd need to head to the Cote D'Azur to find some cool respite. 

10 day ECM anomalies upping by the day now. From a US site so deviations are expressed as Fahrenheit:

A certain Brian Gaze being quoted widely in the papers 

“ Then during next week the mercury will continue to rise said Brian Gaze, a forecaster at The Weather Outlook. At the moment long-range computer models are suggesting an increased likelihood of very warm conditions during the last third of July," he said, reported the Independent.

“Temperatures in the UK reached 32.7C earlier this month and typically the hottest weather of the summer comes in July or August. In recent years periods of extreme heat have become more common in the UK. I wouldn’t be surprised if temperatures climbed to 35C. To put a little context on that, the hottest day in the entire decade of the 1980s was 34.4C.”

https://www.mirror.co.uk/news/uk-news/uk-weather-forecast-hotter-barcelona-27398826 

Corals 5/4 on  for July  being the hottest month ever for the UK 

William Hill 25/1 for the UK record to be broken (that was yesterday's price and looks a good bet, but may have changed)

Having just experienced +100f for the first time in years (Saturday in Valletta tipped the mercury at 39c/102f), I can say that it holds less attraction for me these days.

(although the following day seemed more oppressive at 34c - because the humidity had jumped)

GFS 06Z goes for a short and intense burst of heat. (Static image)

I want to see it but it would be a struggle for me and my breathing!

I also want to see it to because this type of event gives credence to the "warming" theory which many are sceptical of.

I started 13 days off today so ideal timing.

One thing now seems certain: there is a big dome of exceptional heat which will build over the next few days in North Africa and Iberia, and it will break out into Europe. The uncertainty is how far North and East it travels. Does it reach across the Med into the Alpine countries and Balkans, or North into France and the low countries (and Britain)?

Here's Spain and Portugal this weekend in the 06z GFS, with a 50C in Southern Portugal:

Earlier this month? Are they recycling an old quote?

https://weather.meteostar.com/forecast?location=EGMD

584 dam, 27.3 (850Hpa), 33.6c (925Hpa) !

Really? (Link doesn't seem to show forecast for me).

The UK record 925mb temperature is apparently 29.2C on 25 July 2019: https://twitter.com/WorldClimateSvc/status/1155933406359724033

You will need to zoom in. Heat peak is 18.00hrs on 15/7.

OK so to help out and explain what I've been doing with ensembles I introduce to you the Adiabaitc lapse equation!

Its quite simple.

Take your temperature at 850hpa and multiply by 1.053 and you will get what the surface temp should be in ideal conditions! Again for these extreme hot plumes this is going to be a good approximation. Again you will need a low humidity and cloudless skies for this to be reached.

The equation is in kelvins so for 25C at 850 you have to do (25+273.15)*1.053  - 273.15 which gets you 40C

Applying this equation for a few T850s we get:

T850 22C -> 37.6C

T850 23C -> 38.7C

T850 24C -> 39.7C

T850 25C -> 40.8C

T850 26C -> 41.9C

T850 27C -> 42.9C

T850 28C -> 43.9C

T850 29C -> 45.0C

T850 30C -> 46.0C

T850 31C -> 47.1C

T850 32C -> 48.1C

T850 33C -> 49.2C

T850 34C -> 50.3C

You can perhaps see why I got so excited about that 18Z run last night showing 28C on the south coast. So for the magic 40 we do really need T850s above 25C (allowing for a bit of lee way with clouds and moisture) .

Nice. So that record sounding back in 2019 would have given just over 40C had conditions been optimal. I'm not sure what the 850mb temperature actually was when the 38.7C record was set - by 00Z the following day the 20C isotherm was pretty well hugging the east coast.

This is a good site for discussion of the 2019 heatwaves - the graphic comparison of the soundings really shows up the differences. https://www.stratusdeck.co.uk/blog/the-anatomy-of-a-mega-heatwave

Great link, thanks!

Will add that for that plume, even if the conditions had been optimal I don't think it would have happened because I'm not convinced there is anywhere inland enough in the SW for the sea breeze to not have a major effect. So that plume in 2019 was much too far west aswell as moisture being brought in.

One other factor I didn't mention is that I've simplified the equation by making the assumption the pressure is 1020mb, in higher pressure you don't need quite as high T850s and in lower pressure you need higher ones.

GFS 12z drops the furnace heat.

GEM looks a very hot run though.

Useful, thanks