GFS Op 0z - continues the above with shallow LP drifting northwards into the North Sea but making little impression on revived HP ridging from the SW to Scotland until Thu 23rd when this large area of HP withdraws to mid Atlantic and LP 1005mb swings down from the NW to Ireland. This LP introduces fresher NW-lies, later W-lies, and continues to affect Scotland  while pressure remains relatively high for S England.

ECM to T+240 - similar to GFS though keeping pressure higher to the NW and any shallow LP being quickly snuffed out.

AIFS - London, maxima generally upper 20s C, dipping a little Sun 19th but back up above 30C Fri 24th; previous thundery breakdown this weekend has been written out but after Sat 25th cooler with some rain.  Edinburgh, maxima 17C now, rising irregularly to 23C Tue 21st before dropping back to ca 20C. Trace of rain Sun 26th, otherwise dry.

GEFS - mean temp 5C above norm now, dropping back to norm over the next week and staying there to Tue 28th, generally good ens agreement though op, control and a couple of ens members promising 10C above norm for a couple of days around Tue 21st (only 5C above in Scotland). Small amounts of rain appearing from time to time in different runs after Wed 15th, but sometimes heavy in SW, least likely in Scotland

EDIT: And the 0z has 9 days, one less hot day, then a run of 29s. 

GFS Op 0z - As above; then by Thu 23rd the HP has moved south to ridge across Biscay and the LP has merged with general LP in Scandinavia, turning the winds into the NW (but still a mass of hot air to clear away, except N Scotland). By Sun 26th the HP has been replaced by LP which then moves north over Ireland bringing a fresh burst of heat from the south for Britain. Only by Wed 29th is this LP far enough north to bring fresher westerlies.

ECM to T +240 -  By Thu 23rd the HP is still stuck close to W Scotland and Britain is under a mass of stagnant hot air - no sign of fresher NW-lies.

AIFS - London, dry with maxima 27-30C this week and again around Fri 24th, 'only' 24C between these hotter periods; from Sat 25th, rain and 25C. Edinburgh, maxima 17C now soon rising to 20C with extra peak Wed 22nd and dry; back to 17C with rain from Sat 25th

GEFS - mean temp dropping  to norm Mon 20th from 5C above, perhaps some rain Fri 17th in the S; then a little warmer again to Fri 24th after which some chance of rain esp in NW but no confidence in temps as there is a very wide ens spread.

Yeah the GFS outcome is losing support and another heatwave could be on the cards. 

Not necessarily. Southampton Airport registered 28°C before 2pm and there is slightly warmer air trying to nudge in from the south, associated with the warm front set to drift westwards in the Channel. For official stations, Thorney Island, Exeter and Yeovilton all making 27.

And still next to no rain in the outlook for the southeast. Really could be turning into another bad year for farmers. 

Looking at the 12z as you say, I really think we could see the average daily max for July coming in somewhere around 29c down here, which would be insane. I thought 26.5c in 2018 was the warmest I would see for a few decades at least.

GFS Op 0z - Little change from Sat 18th for a week with hot air being re-circulated around Britain and France. Only on Fri 24th does LP over Scandinavia extend its influence and bring in much fresher north-easterlies. As the the HP sinks southwards, the wind goes round to north-westerly and by Wed 29th low pressure settles over Ireland 1000mb with links to a cool N Atlantic.

ECM to T +240 - splits from GFS after Sat 18th when the high pressure is on the move - and eastwards, not southwards - to become centred 1020mb Baltic Thu 23rd. It's replaced by a trough stretching down from Iceland - much cooler for all though the extreme SE just hangs on to some warmth

AIFS - London maxima mostly around 25C (no 30s) and dry until Sat 25th, then 20C with fairly heavy rain. Edinburgh, maxima 18C to Sat 18th, low 20s C to Sat 25th, then like London cooler with rain.

GEFS - mean temp dropping to norm Sat 18th, warming a little (minimal rise in Scotland) during the following week, back to norm from Sat 25th but both hot and cold outliers appearing at this time. Rain likely after 25th, some possible on Fri 17th in SW

It's isolated though,  GEM,  AIFS look much more warm and settled.  ECM is hot 🔥 

But the dryness continues.

https://www.meteociel.fr/modeles/gefs_table.php?x=0&y=0&lat=51.5085&lon=-0.12574&run=12&ext=1&mode=3&sort=0 

AIFS agrees

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=49069&model=aifs&var=4&run=12&lid=ENS&bw=1 

It’s opp a little on the low side @850,s at the end 

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=49069&model=aifs&var=2&run=12&lid=ENS&bw=1 

Just a few hints from its members that T2 will increase again in around 10 days 

https://www.wetterzentrale.de/en/show_diagrams.php?geoid=49069&model=aifs&var=5&run=12&lid=ENS&bw=1 

Another stunning chart from ukmo for summer

https://www.meteociel.fr/modeles/ukmoeu.php?&ech=156&mode=0 

Again very dry

https://www.meteociel.fr/modeles/ukmoeu.php?ech=156&mode=2&carte=0&type=&archive= 

Generally for Southern districts especially s/e a very warm (maybe not HW conditions but has potential later on))and very dry outlook indeed

STUNNING!!!!!

ECM extended also suggests another push from the Azores high at the end of the month.  That European heat dome never gets too far away

GFS Op 0z - Agrees with the above, and continues with little change until Sat 25th when the centre of the HP shifts SW-wards, allowing weak LP from France to approach the south and another from Iceland to approach the north. The latter survives and by Fri 29th is 1000mb Faeroes while SE Britain continues to suck in heat from the continental heat dome.

ECM to T +240 - agrees with GFS, more emphasis on LP from the north Sat 25th which gets to Norway and generates a more definite northerly over all but the south coast. (ECM's forecast of yesterday with HP in Scandinavia in a week's time has been superseded)

AIFS - London maxima 27C now, dropping to 23C but rising again to 27C  Sat 25th; then cooler at 20C with a little rain. Edinburgh, maxima in upper teens now, also rising at the end of next week but only to 23C; from 25th cooler at 18C with significant rain

GEFS - mean temp dropping to norm Sun 19th, a slight rise for the following week (mainly in SE, a few hot outliers there affecting the mean at this time), back to norm from Sat 25th. Dry until 25th then slight chance of rain in southeast, rather more chance in N & W England, definite and occasionally heavy in Scotland.

Yes looks like a decline to mid 20s and still very dry. And, to stretch the analogy to bursting point, still every chance of the puncture repair kit being found by the end of the month allowing those temperatures to get pumped back up into the 30s 🙂