What’s certain is that there is a “pattern change” about to happen. From several weeks of zonal flow and an Icelandic low, to a blocked pattern with weak jet and high pressure in the North Atlantic. 

The trouble with modelling blocked scenarios when they’re setting up is that small local differences within the large scale pattern can be the difference between heatwave and drought, and deluge. 

There’s certainly scope for extended heatwave this evening, and there’s also scope for some sort of slow moving shallow low situation. 

I don’t think this will resolve until this weekend’s Northward migration of the high has taken place. 

As I expected, the ECM 12z was a big outlier at the end. Pattern change is looking increasingly likely next week.

Outlier yes, but the 850s average are trending upwards again. But don’t worry keep calling a pattern change when nothing is yet resolved past next Monday. 

UKV shows 37C on Sunday.

UKV did very well in the end pinpointing location of the previous max this year. Of course it may not end up being 37C but will be fascinating to see how well it does location wise.

MOGREPS-G highlights the uncertainty next week. The 12Z update taken in isolation still seems to favour another ridge of high pressure building from the southwest.

The all time Welsh temperature record is 37.1C set all the way back in 2022.

As has been noted before, the second half of July (and indeed the whole of August) could be cool and wet, but that’s not what the model output is currently showing.

It's great to see more activity in this thread, but I've had to remove several posts. Unfortunately, that means some of the replies will have been deleted too. 

Just checked the GEFS 12z for my location and it does look more bullish on a breakdown of the heatwave and a slightly quicker change to more unsettled closer to average conditions. I don't check all the other models but from the comments on here it sounds like they are supporting that trend also. I think the last heatwave also ended up less extreme and shorter than some of the models were initially indicating.

As for 37c from the UKV I expect we will more likely top out at about 33 or 34c.

It's down to where the LP ends after the heatwave ends Tuesday.  It could sit right over the UK for a few days or sit to our west and act as a heat pump. I'm not sure I'm seeing significant pattern change though.

But it's very brief. Only 15C during the torrential rain, which swiftly pushes through with temperatures back up to to slightly above average (23C) the following day, and mid to high 20s likely the following day (the run ends at 12 noon with temps already 24C across the south.

I wouldn't describe it as a "pattern change" at all. It shows a low pressure system crossing the country before pressure builds again.

Brian, the activity is caused by one member (apt), and the subsequent replies from those stating what the charts are actually showing. It’s a real shame that it’s not all about the coming heatwave, but as much about someone’s ramblings, but I suppose it’s entertaining and generates site traffic. 

Still looking like we could get the highest temps in this area, and possibly as high as 34c. The tv forecasts are stating 32c here for the weekend, and at a few days out can often undercook (no pun intended) the actual temps by a degree or two 

ECM - as GFS to Tue 15th, but then the trough first moves N-wards, by Thu 17th 1000mb Hebrides before projecting a shallow trough over the rest of Britain Fri 18th.

GEM - closer to GFS though the LP in the week 15th-22nd stays out on the Atlantic and has less influence

AIFS - London: maxima 25-30C to Tue 15th, then a little rain and maxima 20-25C for the following week, rain increasingly probable and quite wet from 22nd. Edinburgh: similar pattern but about 5C lower. Any rain is more front-loaded.

GEFS - In the S, reaching 5-7C above norm by the 15th and dry, then cooler at 2-3C above norm with occasional splashes of rain, quite good ens agreement. In the N, similar temp profile (but norm is of course lower)though the end of the heat is more gradual. Rain quite frequent from 15th and sometimes heavy in the W

Feels like next week is the critical week of the summer: the fork in the road between all time classic and school holiday fizzle 

As mentioned in David's (DEW's) analysis above, the cooldown brings temperatures in the S to 2-3 degrees above average. There is reasonable ENS agreement (with the usual high-fliers) and the mean actually rises again as the period advances. And as for rain on and off, thank goodness for that- my water bills for my wildlife garden are far too high. It also means there are likely to be above average night temps, helping to maintain a high CET.

ECM also brings another brief promise of heat around T+192, and at that frame with that 20C 850 isotherm that close, who knows?

Indeed. Some runs show the low pressure influencing the whole UK, although that’s the least likely option, currently 

Others show it trying to nudge in and mainly affecting the north, whilst it stays warm to the south, and some show the high pressure reasserting across the whole UK, keeping the low to the NW of the country 

Pivotal  

It seems to boil down to where the high pressure "block" ends up. As it moves north it will encourage lower pressure over the UK and therefore cooler and more unsettled weather ensues. But longer term most models currently show the block either dissipating and re-establishing over the Azores or sitting over Greenland. 

Interesting model watching ahead.

PS: I'm missing my fellow Kent weather forecaster sensei that is Steve "Gusty" Wall as he is still in the process of recovering from his stroke. 

MOGREPS-G shows things quite nicely.

Can I just say, I don't get the high surface temperatures. I feel like 10 years ago, you didn't get mid twenties every time an anticyclone came along, you actually had to get long fetch southerlies. Now it seems widespread mid twenties is the default for any anticyclone

We didn't get as many extreme rainfall events either 😉      

Wonder what could be the cause?  

This feels faster than direct land global warming. Is it a soil moisture/SST thing? 

GFS 06z at 288hrs and looking like it’s limbering up for a cheeky second heatwave at the end of the run. 

6Z goes hot then blip then hot, rinse and repeat