I doubt there's much tweaking going on at this time of day... I'd suggest it's more likely the newer UKV run came out in the meantime.

(IIRC they're run every 3 hours, hence the relatively common bobbing up and down of temperature forecasts during the day).

EDIT: Here we go:

https://www.metoffice.gov.uk/research/approach/modelling-systems/unified-model/weather-forecasting

UKV:

- run hourly out to 12 hours (unless shown below).

- run at 00z, 06z, 09z, 12z, 18z, 21z to 54 hours.

- run at 03z and 15z out to 120 hours.

 I suspect the 03z run was what changed the forecast... I'm guessing it takes a little while for them to update. All eyes on the 06z update!

Thats real useful info Darren. Thanks. 

Most sites starting the crystallise around the 36C—37C now. Astonishing really. We could still get the FOURTH hottest day ever recorded.

There seem to have been some subtle changes in the model output to delay/moderate the start of the heat but make it last longer. Arpege now goes for 35C max tomorrow (actually checking the TWO charts there is still one solitary 36C gridpoint), but it is now up to 35C for both Saturday and Sunday.

Overnight lows look pretty remarkable with 21C or 22C possible along the south coast.

GFS goes two degrees higher on Saturday than on Friday:

Fri 33, Sat 35, Sun 33, Mon 34, Tue 33, Wed 32.

Horrific stuff. My fridge is already giving trouble and perhaps will pack up due to this

Lots of drunk fools will be out on the streets as well

Arpege ensembles imply a ~50% chance of >35C on Friday

20% chance of >35C on Saturday

5% chance of >35C on Sunday

My gut is that we are all going to be dissapointed on Friday.

That what happened last week was wierd, and exceptional. And this will turn out to be a normal heatwave as the uppers imply.

May be wrong but I doubt we will see mid 30s for 5 days. Certainly Friday but I doubt we will get close to the record like we did last week.

Tbh though it kinda feels like mid 30s is the new normal, I can't remember the last time we didn't see mid 30s at least once per summer.

GFS 06z shows unreal heat:

Friday: 34C

Saturday: 34C

Sunday: 33C

Monday: 33C

Tuesday: 34C

Wednesday: 34c

Thursday: 34C

Friday: 29C

Adjusting for local conditions and model resolution temperatures could well be higher. 

That sort of heat is what GFS was showing a few days ago, before dropping it and showing a quick breakdown by Sunday. Now it's flipped back to what it was showing originally. Funny how often that happens.

Have the Metoffice released a heatwave warning yet. Surely this qualifies.

EDIT: I can see they have. Does anyone know the criteria for a Level 4 - Emergency?

A very difficult week ahead. 

A level 3 heatwave alert is in place for; East of England, London, South East England and the South West

Current watch level: Level 3 - Heatwave Action

Issued at: 08:47 on Thu 6 Aug 2020

There is a 90 % probability of Heat-Health criteria being met between 1200 on Thursday and 2100 on Tuesday in parts of England.

This alert updates that issued at 10:53 Tuesday 04 August. The alert has been extended in time for all previously affected regions of England, now extending to Tuesday. The alert level has increased for Southwest England, as confidence in hot weather and warm nights affecting at least the far east of the region has now increased. The alert level in all other regions remains unchanged. Hot or very hot conditions are likely across southern, central, and eastern parts of England from Friday as warm air spreads north from France. These conditions are likely to persist into the weekend, perhaps being eroded from the northwest by less hot and cloudier conditions for a time, with the slight releiving conditions currently probably reaching a southern limit over central parts of England. Hot or very hot conditions may then extend further northwest again early next week, but with an increasing risk of some heavy and thundery showers developing that will add significant uncertainty and limit the range to which this alert can be issued. Given this uncertainty, there is potential for this alert to be extended in time again near expiry, with this more likely for regions further south and east in England. This forecast is under daily review, but with an update most likely to start the new working week.

An update will be issued when the alert level changes in any region. Alerts are issued once a day by 0900 if required and are not subject to amendment in between standard issue times. Note that the details of the forecast weather are valid at the time of issue but may change over the period that an alert remains in force. These details will not be updated here unless the alert level also changes, the latest forecast details can be obtained at the following link: http://www.metoffice.gov.uk/public/weather/forecast/#?tab=map

https://www.metoffice.gov.uk/public/weather/heat-health/?tab=heatHealth&season=normal#?tab=heatHealth

A level 2 heatwave alert is in place for East Midlands only

No heatwave alert is in place for; West Midlands, North West England, North East England and Yorkshire and the Humber

Exactly. Grim.

Cloud is the most massive issue and kept interfering when we don't want it or on the process to have a heatwave. now is after 1pm and haven't cleared but it was clear all night for what? why bother to come now right after sun rise which his the common behavior this year?  It warm here but air quality very poor.  Was it clear this morning over your area?