Heatwave air mass (updated)

“We quite often see warm southerly air from the continent bringing these high temperatures to the UK in summer, however this week the air across the UK has arrived from the Atlantic. This Atlantic air will descend and warm up as it moves across the UK and this, in combination with clear skies and strong late-June sunshine, is why we are seeing temperatures rise.”

The Met Office’s chief meteorologist, Dan Suri
The Guardian 24 June 2020
Courtesy of UKMO

I don’t want to get pedantic about this, because after all the atmosphere does rotate eastward in the same eastward direction that the earth spins, so in general all our air is maritime in origin, but the current heatwave being experienced in parts of the southeast England looks to me is from continental air that has been warmed over France and the low countries, and has been carried here by winds rotating clockwise around an anticyclone over Denmark. That process is pushing a warm front, and what remains of any ‘Atlantic’ air that was over Scotland, away to the northwest. I can see that the air will have been descending and warmed by the anticyclone, they may been more southerly at height, but surface winds in the last couple of days have been more easterly than southerly over the southeast of England.


I received an email about the ‘heatwave’ airmass and a plot of the backward trajectory the air that was responsible for it. The additional information hasn’t changed my opinion about it, but it might yours.

I find your blog very insightful regarding the analysis of current and recent weather. However, I would like to offer some thoughts regarding your recent heatwave blog entry which suggests the source of the source of the warm airmass is of strictly continental origin around the southern periphery of the high pressure cell (i.e. central or eastern Europe as the graphics suggest). Performing a parcel back-trajectory over the past few days reveals the airmass that resided over southeast England yesterday was indeed of Atlantic origin and had descended considerably through Monday. Whilst this would have briefly passed over the Low Countries it would have been for little more than a day with the significant proportion of the warming of this parcel occurring via adiabatic descent beforehand. From 3000 metres at the dry adiabatic lapse rate, this would have been equivalent to around 29 Celsius of warming.
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