Environment & Energy

hatrack

(59,587 posts) Tue Oct 25, 2022, 08:00 PM Oct 2022

Late-Season Storm Smacks London W. Hurricane Winds; Temps There +/- 10F Above Seasonal Avgs.

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A broken line of thunderstorms formed over the northern end of the Bay of Biscay along France’s west coast during the afternoon hours, expanding into a broken line oriented northwest to southeast as it crossed over northwestern France. As the storms progressed northeast, they tapped into anomalously warm and humid air and intensified.

The Associated Press reported 60 homes were damaged in Conty and O-de-Selle, France, about 40 miles south of where the tornado occurred. It’s unclear if the damage was associated with an earlier tornado from the same thunderstorm or the result of straight-line winds. Intermittent minor wind damage occurred in Belgium and the Netherlands, too.

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Temperatures over the past five days have run about 10 degrees above seasonal norms for this time in France and across the U.K. That allowed for the buildup of sufficient CAPE, or Convective Available Potential Energy — or fuel — for strong storms. What was needed was a trigger. Meanwhile, a dip in the jet stream filled with high altitude cold air, low pressure and spin, was parked over the northeast Atlantic at the same longitude as Iceland. Around that broader trough, smaller shortwaves, or more localized disturbances, have been rotating.

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A French storm chaser captured a photo (below) depicting a rotating thunderstorm, known as a supercell, which appears to have produced a tornado. On the right beneath the storm, dark curtains of rain and hail can be seen cascading to the ground in the downdraft region of the storm. Toward the left, or south, a brighter rain-free region can be seen. That’s the updraft region, characterized by upward-moving air spiraling into the storm.