Storm initiation in MDT risk area in France – Jul 18, 17:10 UTC

New wave of storm initiation is now ongoing in the Bay of Biscay. Several thunderstorms are visible in EUMETSAT VIS imagery as of 16:30 UTC. Current surface data indicate surface temperatures in the 28-32 °C range and dewpoints in 20-23 °C range in SW France, whle T/Tds in NW France are a degree or two lower. Very high instability is in place. Backing easterly and southeasterly winds combine with a strong SSW mid-level jet to produce a highly sheared environment with strongly veering vertical wind profiles. Conditions are favourable for organized thunderstorms, particularly supercells. Storm coverage is expected to increase as a MCS forms during evening hours, moving across the Bay of Biscay into NW France and further north into during the night. Main threats with these storms include torrential excessive rainfall and consequent flash flooding as well as severe wind gusts, large hail and a possible tornado.

16:30 UTC VIS EUMETSAT image of France. Source:

SBCAPE forecast valid for 19Z. Source:

See our previous entry for general discussion on today’s setup in W France. This region was issued a MDT risk area in Day 1 severe weather outlook for today. Today is the first day in a 4-day active pattern over CNTRL Europe and CNTRL-E Mediterranean/Balkans.