Tornadoes in France since 1900: A chronology and spatial analysis.

Since 1900, France has recorded annually 22 tornadoes of low to moderate intensity. Here we investigate the spatial distribution and seasonal patterns of these tornadoes, and document some of the meteorological situations in which they have occurred. We further produce (i) a synthesis of the areas where thunderstorms are formed, with the aim of better understanding the environments favourable to thunderstorm development in France; and (ii) a national tornado risk map emphasising areas exposed to tornadoes in relation to population density. The results of this study are based on data from the Météo-France major events repository (BDEM), the European Severe Storm Laboratory (ESSL/ESWD), and the Keraunos database. This combination results in a complete inventory covering the period 1900-2022. The events selected for the study were analysed in a Geographic Information System, and data from different meteorological reanalyses, such as the GPM IMERG (NOAA NCEP/NCP) and ERA 5, were used for defining the formation zones of a selection of tornado events in the highly affected region.

The spatial distribution of tornadoes in France highlights three vulnerable areas: the north (Normandy, Flanders), the Atlantic west (Poitou, Charentes) and the Mediterranean coastal belt (Languedoc, Provence, NE Corsica). Whereas monthly results highlight a systematic concentration of tornadoes during the warmer season, their spatial distribution appears to be a function of topography- and land-cover-related factors. Specific zones of tornadic storm formation over the Bay of Biscay and the Mediterranean Sea also feature prominently, and these are expected to continue generating tornadoes in the future. The high-risk areas include densely populated urban regions, especially in northern France and near the Mediterranean.