I think we can start thinking about throwing in the towel on any heatwave. GFS is really quite cool now and brings a one day wonder. UKMO is backing away towards GFS and GEM looks to be doing likewise before picking up another hot signal later.
Whatever anyone says about GFS, if it is the first model to pick up on something cruddy, and resolutely sticks to its guns, the rest will almost always follow.
I fully expect ECM will start backing down today as well.

I disagree UKMO is still extremely hot to the end of its run. It's the GFS that has moved towards the ECM this morning.

I read this. Not sure what charts you’ve been looking at this morning. We’re you still asleep and imagined it?

GFS wasn't a cached version though and it looks really rather cool and increasingly unsettled after Saturday.

I wonder if GFS will be on the money as it has resolutely stuck to its guns and is getting cooler with each passing run.

Yes as expected the 00Z ECM is much cooler. Although having said that the GEFS do look to be extending the warmth a bit compared to yesterday, but nothing very extreme. 

It had to really following yesterday's completely implausible 12z. As I said, I am and remain 100% certain that would never verify. 

A quick two day hot spell for the southeast followed by a return to cooler (though still pleasant) and changeable pattern to see us through the last month of summer 2020 is my call.

That said, I think overall, August is shaping up to be the best month of an otherwise nondescript summer.

EDIT. That  ECM from last night is but a distant memory, a figment of all our imagination. I knew it was a completely ridiculous implausible outlier, but the 0z appears much more sensible and stable, prolonging the pleasant pattern but without the frankly ridiculous uppers. In fact its done a complete vaulte face and gone from a scorching southeasterly to a cooling northwesterly at 192-216. The complete opposite. Shows clearly that the ECM and its supposed good verification isn't all its cracked up to be.

10-day summary continues to show NW/SE quite steep gradient in temp; rain in the NW in week 1 but along the S coast in week 2.

GFS this morning shows W-lies turning SW-ly with HP ridge Azores - Norway established by Sat 8th weakening (very warm except N Sea coast may be cooler with light NE-ly; Faversham temps on MetO go down with a bump on Sunday) LP working up from the S Wed 12th and wallowing around, a little cooler, until Mon 10th when the ridge re-establishes from the SW. 

GEFS very warm in S (5-7C above norm) until Thu 13th then dropping sharply to norm (and control run well below) out to THu 20th. Many more rainfall spikes than yesterday spread across different runs from Wed 12th but no consistent agreement. Scotland and N England see less of the heat with temps somewhat above norm around  Fri 7th and Wed 12th but otherwise flatlining around the norm; early rain spike tomorrow 95th) for lowland Scotland otherwise on the dry side for Scotland but quite a lot of rain on and off for N England from Tue 11th onwards

ECM similar trends to GFS but keeps pressure higher Sat 8th and LP from the S on Wed 13th much less well developed as a definite feature.

i think we all knew that. But it was a plausible, if very unlikely.

GFS has moved to a less progressive solution in the medium term (the weekend) is . Not bothered what it does from 144 as we need to get that low modelled correctly first. And I still think that none of models have got a handle on it yet.

This EC run would still have 30s in the south for 6 days in a row (Fri-Wed). Still a lot of uncertainty though (in both directions).

Yup - I got my hopes up when I saw people talking of downgrades (as that means upgrades for me!), but nope... still very warm, if not hot (5 days in a row of >16C 850s down here, for example).

GEFS has had a big downgrade (for me) since yesterday too, with the mean 850s rising from 10C on the 9th/10th to 15C on this morning's output. The surface temperatures haven't risen anywhere near as much, but it's a risky game as it's entirely dependent on wind direction... it has to be just right to ensure cooler conditions with such high 850s and the law of sod dictates that it will change between now and then!

Either way, I'm expecting today to be the "coolest" day for some time - and that's saying something, as it's still going to be at or above average!

Probably the most sensible and accurate comment in here today.  Exact details of the evolution this weekend onwards UK wide are pretty uncertain IMO.

Don't look at the GFS Op alone. If using GFS, consider the ensembles.

Tuesday next week- mean of all Ps in the South still 27°C and 850s above 10° for the whole of England, more like 13-16 for the southern half. Out of the 21 options, only 5 project a temp below 26 in the south with one more than that offering 30+.

So whilst at that range (T + 186) anything could happen, tbf I think it's folly to make such a firm call at this stage, especially when it's clearly not evidenced in the models.

The glorious summer in the extreme South continues. Warm today. Then warming/hotting up and remaining hot for the next week or so according to the latest runs. Not much rain about either. Fantastic stuff. Hopefully the more Northern reaches of the UK can tap into the heat.

Heat seems to be gone temporarily by Sunday with rain in the south monday , still pretty warm though

I'd say the ECM has gone 25% towards the GFS and the GFS has gone 75% towards the ECM if that makes sense.

Still this morning we have 5 or 6 30c days with a couple 35c days, very significant heatwave by UK standards.

Out come the 06zs, and it seems the compromise consensus is now upon us at least for the weekend. Secondary high moving across the North, heat hanging on for Saturday, Sunday fresher for most, but poised for what looks like a second warm up next week.

I find the Meteociel table view a very good way of getting to grips with the GEFS ensembles. For example here are the 850s for London:

https://www.meteociel.fr/modeles/gefs_table.php?ext=1&x=&lat=51.5085&lon=-0.12574&ville=Londres

Run 13 in particular keeps them at 16-18C for a full week.

Fairly unanimous on a cooldown for the end of the run (just when I am going on holiday of course)

But 2m temps still have plenty of reds implying low to mid 70s Fahrenheit which is pretty decent:

https://www.meteociel.fr/modeles/gefs_table.php?x=0&y=0&lat=51.5085&lon=-0.12574&run=6&ext=fr&mode=7&sort=0

Too early to tell with GFS, but sod's law would involve GFS improving significantly while ECM goes cold and wet.

UKMO pushes the heat east Saturday probably still 32c in SE. Friday looks very hot 100f possible. Sunday cooler for all mid 20s at a guess heat pushing back west Monday.