A trade-off with this scenario for southern England is that very hot air isn’t drawn across on Monday, so instead of a day in the mid-high 30s followed by a drop to the mid-20s, we see high 20s to low 30s Mon, with the following two days at least slightly hotter.
The overnight UKMO & GFS runs have made a significant adjustment for early next week with no passage of low pressure near or across the UK.
Instead high pressure holds firm with temps continuing to rise through at least Wednesday.
Will see where this sits in the ensemble later.
A few runs in the 06z GFS ensemble have 850 hPa temperatures above Reading peaking at 23-25°C on Monday 22nd June.
Potential max temperatures at 10 m from that would be in the high 30s to low 40s °C.
A low probability scenario but it's remarkable to see it represented at all.
It shouldn't be taken very seriously a it's just one run of a hardly very reliable model, but the GFS 12z produced a record-hot second half to June for the Hadley CET zone, enough to lift this month from 108th warmest as of today to 4th warmest by the end. A May 2026 redux 🤨
Not many years ago seeing 39°C predicted by a GFS run for London would have been astonishing, even when looking 12 days ahead.
Now it still draws attention but with past experience telling us that yes, it really can become that hot in this part of the world.
I'm not sure I've ever seen a stronger signal from the ECMWF ensemble for sustained very high 500 hPa heights across a large part of Europe at the 5-7 day lead times.
With that comes persistent hot or very hot weather in western Europe, what looks to be a high-end event.
Those pink shades over parts of central Europe for 18th-23rd June represent temps 10-12°C above average for the time of year. An extreme event.
For context here in England, a +10°C anomaly requires e.g. a daily min temp near 20°C & max temp near 35°C. Imagine 5 days of that.
Not GFS' best performance with this area of wet weather crossing southern England.
UKV fared better, though it focused the higher rainfall rates too far north.
Saw 1.2 mm of rain here in Verwood, dropping the 2 m temp to 17°C - the return of summer has taken a short hiatus!
Even when looking at 11-15 days ahead, the ensemble strongly favours a powerful ridge persisting over a large part of Europe including at least southern UK.
However some caution is advisable as the models can be prone to overdoing self-reinforcement of such blocked patterns.
This signal has remarkable persistence through to 10 days time, with only a small ~15% cluster suggesting the high might start to move on.
The others suggest an increasing propensity to encompass at least part of the UK, perhaps Ireland too (hot weather becoming more sustained).
