Only four days away now yet still a significant difference between UKMO and  GFS in terms of how strong the section of the ridge to the west of the UK is versus that to the east.

GFS has actually reverted more toward the stronger western feature compared to the previous two runs. Typical! At least it doesn't result in anything worse than some fresher air although it does turn rather cool near and along the eastern coasts.

Pleasing to see the HP ballooning strongly across the UK on the UKMO run while GFS also has it drifting steadily east. The models have converged here in terms of the SLP pattern, but UKMO has brought less in the way of cool air into the circulation so it would likely be warmer for central parts than what GFS shows. Slack winds mean cooling of easternmost parts should be mostly down to sea breezes on this day.

Not clear whether it would still be very warm in the far south; it's a fine margin between that and something more like 22-24*C.

As the ridge slows its progression and retains decent strength, and with the shallow low heights over Europe not giving rise to heat lows (cool air unable to achieve sufficient temp gradients far enough from the ridges) there are signs of a classic extended fine spell for the UK with temps gradually heading back upward after the freshening up Mon-Tue (latest to occur down south, if at all here).

Given these two runs, it will be interesting to see whether ECM backs down with it's development of 'heat lows' from Europe and interplay of those with what has also tended to be a stronger N. Atlantic jet than UKMO and GFS are predicting. This latter disagreement likely relates to ECM propagating some MJO activity east from the Atlantic to the Indian Ocean while GFS and UKMO keep it stalled out in the Atlantic. The 12z update of the ECM projections for the MJO kept the propagation but weakened the magnitude of it quite a bit so there's hope for the model to tone down the jet stream strength this evening. Fingers crossed as it offers a means of getting the very fine weather right up north.

I normally end up being happy enough if it's over 16°C (counts as warm here) and overcast!

Excellent, detailed analysis SC; thanks. I think also that a persistence of HP, leading to continuous compressive warming & drying; and an increasingly dry surface, could give way to higher temps than the 'baseline' model. Hampshire could be a good place to be over the next week +.

Any forecast for next week i have looked at shows a breakdown next week from Tuesday with either a thundery low developing over Biscay and pushing slowly N.E or a front crossing from the west putting us back in a westerly flow and unsettled or mixed thereafter. Sunday , Monday look fine and hot though.

The point there is that, despite an implicit and superficial consensus of outcome, the two routes are not in agreement, meaning there is no consensus. The two outcomes are as different as a breakdown, and not a breakdown. An increase in different routes to the same end, is actually a decrease in confidence.

ECM increases the persistence of the HP compared to its previous few runs. Could it actually be the model playing catch-up to GFS for a change? Looks impressive for the SW on Thursday with the highest temps in this region which is different to the tendency of many recent summers.

As for Friday, well...

Given the run-up of often very warm and dry conditions, light winds and only gradual destabilisation, I daresay that'd have the hottest spots pushing close to the mid-30s.

We do then finally see the breakdown overnight into Saturday with a fresher, showery sort of day to follow. Sunday sees things improving in the south but remaining dodgy up north... too far ahead to pay much notice to at this time though. It gets there via extensive blocking across the Arctic including Greenland, but ECM's been having a thing for that on and off for a good few weeks now without success. I reckon as long as global atmospheric angular momentum (GLAAM) doesn't fall as much as GEFS has been predicting (usually a safe bet), things shouldn't deteriorate too much in the 10-16 day range (a big GLAAM fall encourages the Azores High to ridge N rather than NE, with a trough dropping in across the UK and surrounds. No surprise to see GFS doing just that at the moment but in theory it's a load of dog doings!).

Some very high temperatures on offer next week as high pressure setting itself up slap bang over the UK will create our own heat pool. 850Hpa's do not necessarily need to be approaching 20c to achieve the mid 35c at the surface given this potential setup.

Those extreme temperatures in 1976 were achieved with 850Hpa's in the range 13-15c IIRC.

A fascinating situation potentially. Its a rare beast to get high pressure aligned favorably and for a persistent period so close to the solstice.

Interesting indeed and this weekend 30C temps are foretasted despite uppers only 13C.  With near to longest day, already dry ground will help to boost higher temps next week.

2013... 2014... perhaps 2017?? Still rare with 3/5 summers?

2010 also had a lot of high pressure around June and some spots did hit 30C ,but after such a cold winter if i remember rightly the seas around NW Europe & UK were unusually low still? This effecting any real heat being built.

We are on holiday in Whitby next week. Not sure what the weather`s going to be like there, but taking some wet weather gear just in case.

It's worth noting the last GloSea5 update strongly supports above average temps in July and August. In the medium term a mixed period still looks the forn horse, but the long term seems promising. There doesn't seem much to suggest a pattern change im our hemisphere. I'd not be surprised if this summer turns out to be very warm.

Even 24 hours later with the 850s at 16C+, the max temp is only given as 26C.