This seems to have been a repeating pattern this year: harmless
looking 'temporary thundery spell' heat lows coming up from the south
then deepening and dragging in cool, damp air from the Atlantic,
unexpectedly ending a settled spell (I'm more used to these thundery
lows just coming in, hanging around then drifting off again). Happened
on May 25th and June 13th, and the latest GFS (yes, a long time away I
know...) for July 11th suggests the same sort of thing happening again
following a week-long relatively settled spell for England and Wales.
What actually causes this to happen?

wrote:
This seems to have been a repeating pattern this year: harmless
looking 'temporary thundery spell' heat lows coming up from the south
then deepening and dragging in cool, damp air from the Atlantic,
unexpectedly ending a settled spell (I'm more used to these thundery
lows just coming in, hanging around then drifting off again). Happened
on May 25th and June 13th, and the latest GFS (yes, a long time away I
know...) for July 11th suggests the same sort of thing happening again
following a week-long relatively settled spell for England and Wales.
What actually causes this to happen?



Is it something to do the the sea surface temps around the UK being
higher than usual? I read somewhere that the hot summer last year,
caused the sea around the UK, to heat up more than usual.

--
Joe Egginton
Wolverhampton
~175m ASL