T oday is the day when Benjamin Franklin supposedly flew a kite in a thunderstorm, to prove that lightning was electricity. We have learned a lot about thunderstorms since 1752, but our fascination with them has not diminished: who can resist the energy in that crackling drum roll, the angry purple clouds and those brilliant fleeting flashes of light?
For nearly 200 years aficionados in Oxford have been measuring thunderstorms. Analysis of this uniquely long record has been published in the journal Weather, and reveals a marked drop in the number of thunderstorms in the Oxford area during the last decade. Curiously the 1920s and 30s were peak thunder years, with an annual average of 20 days of thunder heard. By contrast, the most recent decade averaged just 8.1 days of thunder a year.
Contrary to popular belief, Stephen Burt from the University of Reading has found that hot weather and thunderstorms do not automatically go hand in hand. Analysis of the Oxford data shows that particular weather conditions such as “Spanish plume events” – south-easterlies bringing warm air from the Iberian plateau – are better predictors of thundery days for southern England, and that possibly the reduction in thunderstorms in the last decade is associated with a reduced frequency of these kind of weather patterns.