Climatology of severe hail precursors in Czechia

The severe hail observation in Czechia is limited to observations from weather stations and reports from the public. More comprehensive information can be obtained from weather radar measurements. A method based on single-polarisation techniques has been developed to detect severe hail causing significant damage on the Czech territory. However, this is limited by the period of radar measurements. Insight into the climatology of severe hail is gained by studying the environmental conditions suitable for large hail development.

The ALADIN/PERUN reanalysis includes outputs describing the convective environment. The reanalysis has high horizontal (2.3 km) and temporal (1h) resolution in the 1991-2020 time span. The environmental parameters CAPE, CIN and wind shear are tested in this work as precursors of severe hailstorms. Precursor values that can be used to develop a climatology of hail hazard in Czechia are obtained by comparison with radar-based hail detections from the warm parts of the 14 years from 2007 to 2020. The presence of precipitation ice in convective precipitation as identified by the ALADIN/PERUN reanalysis will also be examined.

In addition, case studies of hailstorms in the vicinity of the mountain meteorological observatory at Milesovka, where more focused radar data are available, are prepared and the precursor values are discussed.