As a first year student at Reading Uni in 1994, this day in
that year was one which sticks in my mind - less for the maths exam I dashed
through (passing, thankfully!), and more for the intense thunderstorms which
developed/moved north during the evening.
It was a reasonably classic deep southerly flow, perhaps a
Spanish Plume:
During the previous evening, AcCas blossomed across the
Reading sky as the EML drifted north - the 12Z Herstmonceux sounding from the
24th shows a pronounced EML. Modifying this with the Camborne 12Z 900-700hPa
temperature profile (making a very broad assumption that the approaching upper trough
from the west caused cooling via lifting above a capped boundary layer, across
eastern areas, leading to a similar 900-700hPa profile to Camborne's) and using the max temps (29C) and approx dewpoints in the warm
sector yields sizeable and deep CAPE. As the trough approached upper flow
increased too, with enough shear for well organised multicell thunderstorms,
and perhaps updraught rotation.
From my point of view, after finishing the exam I went back
to my hall - after dinner, at around 6.30pm, a large, thick cirrus shield
overspread the sky from the south. About an hour or so later a thunderstorm
commenced, bringing frequent lightning, strong winds, and plenty of rain. It
went on for a couple hours before moving away - it was a very impressive storm
although I think the storms further east were even more intense.
Here is some BBC forecast footage:
And some YouTube footage from a chap in
Great Baddow, Essex:
Great Read !
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