In message , Philip Eden
writes
Unusual line of very sharp showers shows up on the 1300
radar stretching across south Oxon, Bucks and Herts.

I've seen this before, though rarely, when vigorous
cumulus penetrates the overhanging altostratus shield
of an ana-coldfront.

Martin ... mechanism please !!

Philip Eden

Had a short burst of torrential rain in Chalfont St Giles from one of
these showers. The raindrops were about as big as any I have seen.

Norman.
(delete "thisbit" twice to e-mail)
--
Norman Lynagh Weather Consultancy
Chalfont St Giles
England