I took an interest in this after the last discussion here a while ago.I was pretty sceptical about
the attribution of true supercell characteristics to storms in the UK.
Apart from the Wokingham storm other candidates (mostly on circumstantial grounds ) for warm season
type supercells might be the Dover storm ,14 Oct 1964 (Pedgeley,Weather1965 p351 and following
correspondence),the Wiltshire Hailstorm July 1967 (Hardman ,Weather 1968,p404,and the South Coast
Hailstorms June 1983 (Wells specifically calls them 'supercells' based on satellite imagery,Weather
1983,p369)..
The West London tornado,December 1954 parent storm might be a candidate for a low topped
supercell.Radar imagery put the Cb tops around 22,00ft.
Except for the Wokingham storm the lack of diagnostic radar data gives good ground for Will's point
of view .The problem is that when 'Supercell' is mentioned US 'High Plains' storms are conjured up
and these just don't occur in the UK.Better candidates for supercells have been identified in radar
imagery in Switzerland,Italy and France.
On the otherhand,IMO, there is a better case for low topped ,cool season 'mini' supercells in the UK
in analogy to similar storms studied in eg Australia,California and Japan.The storm chase pages
posted for March this year are v interesting and provide good circumstantial evidence.More studies
like this are needed,but how you'd organise a full blown scientific study of them with doppler radar
I don't know.Perhaps the CSIP project will get lucky.In any case it's about time somebody wrote a
review of the case for UK mini supercells .I don't know whether this throws any light on the
problem-
Quarterly Journal of the Royal Meteorological Society - 2004 papers
Vol. 130 APRIL 2004 Part A No. 598
J. HOLDEN and A. WRIGHT - UK tornado climatology and the development of simple prediction tools
p.1009
doesn't appear to be available freely on line

--
regards,
david
(add 17 to waghorne to reply)