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

[Gordon Webb]

8 minutes ago, ribster said:

Yes, one day wonder here, temp for today slightly revised down and more so for next four days, before dropping away further.

that's a sizeable drop away from south coast / se , not overly cold by any means but still a sizeable drop nonetheless

[MattStoke]

36.3’C at Heathrow currently. Hats everywhere can rest easy  

[mushymanrob]

Today is the hottest recorded August 7th in the UK, previous record set in 1975 at 34c in Bromley, smashed it by over 2c. I bet in the coming days more daily records will fall.

[Guest]

Heathrows dropped back to 35.6C - game over today.

[h2005__uk__]

Strong chance that the max at Heathrow will be around 37C, as the hourly reading at 3pm was 36.3C.

[Man With Beard]

Afternoon all

A really crazy few days of modelling coming up for the southern half - a bit more straightforward, fairly decent summery weather for the north, apart from a shower or two!

Some thoughts: First, because of the uncertainty over cloud and rain, it's going to be nearly impossible to predict maximums beyond 24 hours. There's little precedent in modelling for this set-up - maybe September 2016 is the closest (which produced a 34C). The trouble is, Arome's ability to predict temperatures is not so good when cloud is around I feel, and while Arpege is great at frontal systems, I don't think it performs that well at convection coming from the east. It will be interesting to see  how the HIRLAM does, as it's pretty good on easterlies in winter, though this is probably a totally new ball game. The maximum figure, in my opinion, could be anywhere between 30 and 35C on each day, and perhaps up to 37C tomorrow / Tuesday if the cloud forecast is completely wrong.

Dare I say it - the Met Office might possibly be the best source in this set-up

Edited August 7, 2020 by Man With Beard

[Frosty.]

Looking towards the last third of August, to be sure there are some very good signs from the GEFS 6z!..in the meantime, a significantly better update from Exeter today compared to previous days..but they were preety good to!

 

[The PIT]

Big shift in the GFS  in regards to Thundery weather with main action early in the week being pushed to northern England. Slightly cooler as well but still hot in the south and very warm to hot in north midland and Yorkshire with more pleasant weather to the north of that unless you like heat that is. Sadly it means I'll have to push my water bill up as the garden will need watering most days now. Whats hoping to get away with it.

[mb018538]

GFS kicks the heat away by Wednesday - so if heat isn’t your thing, 4 days to go. After that a few cooler days before high pressure returns for the weekend and starts to warm things back up into the 25-28c range. Much more comfortable!

[Ben Sainsbury]

UKMO 12z on the other hand maybe bringing something a bit warmer again?

T144:

[Captain Shortwave]

The GFS looks kind of in line with general thoughts regarding a breakdown midweek before building the Azores high towards the U.K.

Goodness knows what the UKMO is up to, potentially setting up to reload the extreme heat over Spain by cutting off the thundery circulation that will bring the interest over the next few days.

[Singularity]

Not sure about GFS’ thermal low development Sunday. A bit out of line with other modelling. Changes the wind pattern to one that focuses the heat more in the SE.

The 12z even dares to take that heat low all the way north through the country Tue-Wed. Yet looking at the jet stream charts there’s no support to be found for such movement.

The difference to UKMO for surface max temp potential is in the order of 5 Celsius for Dorset, for example. That model has no wandering heat lows to speak of.

GFS Dodgy = True.

Edited August 7, 2020 by Singularity

[The PIT]

Or it's picking up a new trend. I'm glad in once sense heat wise the direction it's going but not storm wise.

[Man With Beard]

40 minutes ago, Ben Sainsbury said:

UKMO 12z on the other hand maybe bringing something a bit warmer again?

T144:

The ecm clusters played with a plume "reload" a few days ago - they've gone cold on it recently though.

Edited August 7, 2020 by Man With Beard

[SMU]

so 36.3 today unless theres any final updates -

 

A sort of halfway house of the extreme heat forecasts & the 'not so hot ones' - All in all a fair reflection as the cloud edged in- I think heathrow would have been 37/38 otherwise-

Theres always tomorrow where we come from a higher starting point !!

 

As was mentioned above UKMO 144 presents a possible spack reload from the SE which would bring the furnace back as the trough sinks west of the UK- interesting !

[mb018538]

ECM is still humid in a weeks time, the warmer air never really leaving. However with lower pressure, an upper trough close by and a much more unstable atmosphere, there’s more cloud and rain around. So despite 850s being 12-13c, it only translates as mid 20s at best.

[mb018538]

The 12z is more unsettled, whereas the 00z and the gfs run tonight build a high in through next weekend.

Clusters this morning had both as scenarios, and with such differences, we will need to wait and see as time progresses which option wins through.

[Djdazzle]

5 minutes ago, mb018538 said:

The 12z is more unsettled, whereas the 00z and the gfs run tonight build a high in through next weekend.

Clusters this morning had both as scenarios, and with such differences, we will need to wait and see as time progresses which option wins through.

I suspect all of this heat around Western Europe will cause a bit of havoc with the models in terms of where they go next.

[Mapantz]

UKV for tomorrow shows subdued temps compared to a day or two ago:

[Djdazzle]

1 minute ago, Mapantz said:

UKV for tomorrow shows subdued temps compared to a day or two ago:

It did that for today, then increased them again.

[mb018538]

3 minutes ago, Mapantz said:

UKV for tomorrow shows subdued temps compared to a day or two ago:

No way that’s right. 26c over London? BBC and met going 33-36c.

[Mapantz]

Just now, mb018538 said:

No way that’s right. 26c over London? BBC and met going 33-36c.

[Man With Beard]

So on the basis of this evening's ECM, adding 2-4C to raw values (today's max was 3.3C up on raw max for example), this is what could be expected as a UK maximum in the coming days *IF* it is right. (Not far off those outlandish predictions of last weekend!)

Sat: 35-37

Sun: 35-37

Mon: 35-37 (all these three days have a raw 33 somewhere)

Tues: 33-35

Wed: 33-35

Thursday and Friday may scrape a 30 in the far SE, but after that it's over.

If I were to take a punt at temperatures being at the lower or upper end of the ranges given, I'd go for the lower end - I have a feeling the ECM predictions match up better with reality when there's more cloud around. 

A further note (northerners look away...), the heat is not that localized in the next three days - if you're inside an area from Exeter to Birmingham across to Norwich down to Kent, you'll probably see 30C based on ECM predictions on each of these days.

But as I mentioned earlier ... with cloud around, a really good temperature prediction may not be possible until each morning, lots of cloud will kill it, no cloud will see it soar - EDIT @Mapantz post above is a case in point of what too much cloud will do!

 

Edited August 7, 2020 by Man With Beard

[Gowon]

8 minutes ago, Djdazzle said:

I suspect all of this heat around Western Europe will cause a bit of havoc with the models in terms of where they go next.

Why? Does extreme heat in Europe have an affect on weather models performance?

[Portsmouth Sun]

6 minutes ago, mb018538 said:

No way that’s right. 26c over London? BBC and met going 33-36c.

Of course it is not right, all other models that are more highly regarded are no where near this solution.