Severe thunderstorm climatology in the Balearic Islands (2010-2023)

This article presents the first systematic climatology of severe thunderstorms (ST) in the Balearic Islands (Spain) between 2010 and 2023. Thanks to severe weather reports and observations from 111 weather stations, an extensive database was constructed involving 43 severe thunderstorms affecting the islands during 41 severe storm days. A thunderstorm was considered as severe when producing at least one of the following  phenomena: hail with diameter ≥ 2 cm, straight line winds ≥ 90 km/h or a tornado over land. Annual, monthly, seasonal, fortnight, spatial and hourly distributions were analyzed. Autumn months account for 48.8% of all ST, with the highest frequency seen in October. Distribution by fortnights shows a maximum of 7 ST in the second half of August. Convective straight line winds were the most common severe phenomena in ST affecting the Balearic Islands and occurred in 41.9% of all ST. Hourly distribution shows a maximum in the morning hours, between 10 and 12 AM. Spatial distribution shows a maximum incidence in the biggest island (Mallorca) with a mean of 2.6 ST/year. The South of Mallorca followed by the central part of the island are ST hotspots within the archipelago. For every severe thunderstorm day, the mean SST and anomaly of the Balearic Sea were identified using daily reanalysis from 12 UTC on ERA5. The vast majority (84%) of ST that make landfall in the islands are maritime. Peak ST activity occurred with SST in the range of 25-26ºC. Extremely severe thunderstorms showed a maximum with SST between 27 and 28ºC.