A flash flood swept through the Cornish village of Coverack on Tuesday (News, July 19), bringing back uncomfortable memories of the Boscastle flood disaster in 2004. Cornwall has a long history of violent thunderstorms, unleashing torrents of rainwater sweeping down narrow, steep-sided valleys and tearing through towns and villages.
On June 8, 1957, a flash flood ripped through the Cornish town of Camelford when a thunderstorm dropped 20cm of rain over 24 hours.
“It came with such a rush, like a huge wave,” said one eyewitness.
In one terrifying ordeal a woman who rushed to a phone box to call for help found herself trapped inside the booth by floodwaters. Two fishermen crawled across a parapet on a bridge above the phone box and used a rope to rescue her. Four bridges were damaged or destroyed and 50 homes flooded.
The thunderstorms on Tuesday were an amazing sight across much of southern England and Wales. Skies were ablaze with lightning, thunder cracking and rumbling, and torrential rains and hailstones crashing down.
Advertisement
July tends to be the peak of the thunderstorm season, when lightning flashes reach their most frequent across the UK and Europe. That is because the land tends to reach its hottest, and the heat and humidity fuels thunderstorms, with plenty of lightning, hail and heavy rainfalls.
In the UK there is a pattern in the number of thunderstorms over the summer — most frequent in the southeast, far fewer in the northwest. That is because the southeast tends to be hottest and storms arrive from Europe, which is what happened on Tuesday.
In winter it is a different situation. The land is cooler and as a result there are far fewer thunderstorms, yet it is interesting how the northwest coast of Scotland stands out for thunder and lightning. This is thought to be caused by unstable air sweeping over the sea that rises over the mountainous coastline.