The violent tornado on 24 June 2021 in Czechia: damage survey, societal impacts and lessons learned.

A violent tornado occurred in Czechia on 24 June 2021, killing 6 and causing at least 576 injuries. There were more indirect than direct injuries. The tornado was rated IF4 using a draft version of the International Fujita scale. This was the first violent tornado in Czechia and one of only 17 violent, i.e. (I)F4 or higher, tornadoes that occurred in Europe since 1950. The tornado reached the width of 3.5 km, the widest on record in Europe. The case presents an important opportunity to investigate the impacts of such strong tornado in the area, where they are rare, no tornado warnings are issued and where the building standards are different from the typically investigated tornadoes in the United States. We discuss challenges in organizing the damage survey, which took 3 days and involved meteorologists from 3 countries. A wind damage survey guide to aid mitigating these was written by the European Severe Storms Laboratory and initiated the development of a wind damage surveying app. The damage survey showed that most of the inhabited buildings built using heavy masonry and rigid ceilings did not collapse in IF2/3 winds, but only with IF4 winds. Eyewitness reports collected after the tornado show that many people were not aware of the risk associated with the tornado. Eventually, most people tried to shelter in the most secure part of the house, but it was often too late. This case highlights the need for a better communication of tornado risk to the public in Europe.