Just want to emphasise one remarkable aspect of this. Its not a 'plume heatwave' that we are used to. In a plume heatwave, a North easterly wind would waft the heat away quickly; while it has lessened the impact for some really its only had a sea breeze type effect and hasn't changed the temperature of the airmass that much. So what's going on?
This is an 'adiabatic heatwave' or a 'heat dome' which is very very unusual for the UK. Essentially we have a powerful deep anticyclone with near record geopotentials above about 850hpa and extending well above 500hpa. These deep semi-permanent anticyclones do not usually exist at our latitudes. There are basically three in the NHem summer; one over the southern USA, one over north Africa and Arabia, and one over central Asia.
What seems to happen is almost like a 'reverse 2010', instead of a bit of polar vortex breaking off and migrating to latitudes where it doesn't belong; instead we have a bit of the 'hadley anticyclone' break away from north africa and come to settle over Europe and the UK. The air is descending synoptically at levels we do not usually see. So it doesn't much matter what the surface winds are doing if ultra high potential temperature air is sitting 3000m+ above our heads that is easily able to descend and introduce warm air from above. Understand that potential temperature, is the temperature accounting for pressure; its only really cold upstairs because the pressure is low; once you have accounted for the pressure its actually warmer higher up and that's even more the case in ultra thick anticyclones.
I wonder, what happens if we combine 2026 with 2022. We have a heat dome like 2026, but as the dome starts to decay, we get a plume of 2022 magnitudes.
Originally Posted by: Quantum