Can't get MetO 12z faxes on Archive on Wetter, but 8 hours before this on 19th June 2005 produced similar conditions around Thirsk/Helmsley when a supercell storm wandered up from the SE.
http://www.wetterzentrale.de/archive/2005/brack/bracka20050620.gif
I remember seeing it pass by when I lived in York. Looked like a nuclear mushroom cloud.
Originally Posted by: Arcus