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Old June 25th 05, 12:33 PM posted to uk.sci.weather
Keith (Southend) Keith (Southend) is offline
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First recorded activity by Weather-Banter: May 2005
Posts: 458
Default Understanding 'shear' with Storms ?

Have I got this correct with regards the effect of wind shear with
thunder storms?

Yesterday (24th), most of the south of the uk was under the influence of
some very warm air, with some notably high dew points. Cooler air was
closing in from the west which at higher altitudes was moving basically
from west to east, where as the general flow at the surface was between
the SE to SW. The cooler air aloft spread across from the west before
the warm air below had moved on, creating very unstable conditions, some
would use CAP and Li values. But basically the "Envionmentl Lapse Rate"
(ELR) was such that a parcel of hot air rising would be super cooled to
give the effect of the storm we saw yesterday. I think the values are
normally 4°c per 1000ft, or was it metres?

I also suspect the here in the SE, we had a little bit of a home grown
scenario, given the higher temperature and dew point values compared to
the rest of the southern half of the country. Subsequently, between 12
noon and 14:30 the whole thing went "Bang".

So have I got my facts right when I say that the wind shear is the
cooler air aloft moving over a the warmer yet from a different
direction? Also, I would imagine it is this type of shear that can get
the atmosphere spinning and spawn tornado's.

Many thanks
--
Keith (Southend)

'Weather Home & Abroad'
http://www.southendweather.net