On Tue, 03 Aug 2004 18:56:28 GMT, Norman Lynagh
inspired by Deep Thought wrote:

Prolonged thunderstorm here from about 1430 to 1730 BST. Thunder almost
continuous throughout the period with lots of lightning. Although my
field of view is quite limited because of trees, C-G flashes were
visible every couple of minutes throughout the storm. The rain was
nothing exceptional being mostly moderate with occasional bursts of
heavy and a few brief downpours. Rainfall during the storm totalled 21
mm. It was the most notable TS here for some years. Had it occurred at
night it would have been a very spectacular "son et lumiere"

Yes Norman, it was quite some storm, and indeed would have been a superb sight
at night. There were distant "growly" rumbles of thunder here for about an hour
from about 2.30pm, but by 3:30pm things had really hotted up here on the
Chilterns just outside High Wycombe. Almost continuous thunder was coming from
at least 3 different cells, and we had approx. an hour of continuous thundery
rain. There were at least 15 C-G strikes less than 400 metres from my house,
some of them were very spectacular sparks too - extending in two or three
directions at once.

I estimated we had approx 1.5 inches of rain in an hour, and many local roads
were impassable because of floodwater, and there was a lot of debris washed onto
the roads by the fast-running streams of run-off water. Rarely do we get storms
here, usually they miss us altogether but when we do, Oh Boy! Do we get one! It
was the best storm here for at least 5 years - if not longer. It was still
rumbling round at 5:30pm.

Two things are of note about this storm.
1) According to the satellite pictures on www.wetterzentrale.de, these storms
were home brewed: i.e. they didn't blow in, they formed on the spot - possibly
caused by a localised trough-like disturbance or breakdown of a mid-level
inversion.

2) According to a friend of mine who has lived here since 1959, he says we used
to get a lot of this type of storm round here. He says (and after observing
yesterday's fireworks I agree with him) that there was a gentle south-east wind,
and the prevailing wind has rarely been in the south-east during the last 10
years or so, so the scenario for good storms here seems to be that some of
London's heat is wafted towards us on SE winds, and then with the right
conditions, all hell breaks loose when the said hot humid air is lifted as it
hits the Chilterns. Not a Spanish plume as such, but a London plume!!

Nigel

Aagh! Every time I learn something new... it pushes something old out of my brain!