Abstract/Summary

The long instrumental meteorological records from the Radcliffe Observatory site in Oxford (where records commenced in 1772) are well known, and have recently been documented to 2018 by Burt and Burt (2019). Less well-known, and still largely in manuscript or paper format, are the non-instrumental records also maintained by the Observatory which documented the occurrence of fog, snowfall, thunderstorms and the like. Records of thunderstorm occurrence at the Radcliffe Observatory, by date, are complete between 1828 and 1986, excluding the years 1936 to 1970 for which only monthly totals are available. Since 1986 a reliable private record of thunder frequency from Oxford, very close to the Radcliffe Observatory site, has been used to extend the record to 2019, forming a record of almost two hundred years of thunderstorm frequency for the city – a record probably unique anywhere in the world. This newly digitized record, made available for the first time, is examined for long-term (decadal) trends in thunderstorm frequency, and by Lamb Weather Type. Comparisons are made with other long-period records from west London, around 75 km south-east of Oxford. Reasons to account for the marked reduction in thunderstorm frequency in the last decade are suggested.