Graham Easterling wrote:

At 10:00BST it was warm sunshine - peaked close to 18C around 10:15.
Then Cb developed over the bay at a remarkable rate.

Thunder but no rain (so far) I think it passed over Newlyn. A very
localised affair.


Graham
Penzance

Notice Penzance heliport was reporting only a few clouds at 10:20 (and
17C in a mod/fresh onshore breeze). The cloud did develop very quickly
in the next 15 minutes.

Graham