Comparing ERA5 convective environments associated with hailstorms in Poland between 1948–1955 and 2015–2022

Abstract

This study compares the convective parameters between two 8-year periods of hail reporting in Poland: 1948–1955 (period A) and 2015–2022 (period B). The data on hail incidents for period A was derived from hail annuals of the Institute of Meteorology and Water Management, while for period B from the European Severe Weather Database. Period A contains more hail reports (18375) compared to the recent period B (3677). ERA5 reanalysis and thundeR package were used to calculate convective parameters for both periods. Convective environments indicated a more favourable environment for the hail occurrence in period B with larger instability, vertical wind shear and storm-relative helicity. The most widespread event with the largest hailstone ever documented in Poland (14 cm) also occurred in period B, on 24 June 2021. However, the mean number of hail reports per day was higher in period A due to a more effective method of hail reporting. In both periods convective environments were also clearly more favourable for hail in the days with hail exceeding 5 cm in diameter compared to the days with smaller hail and in days with the large quantities of hail reports. This study showed that ERA5 was able to capture convective environments reliably well for events as old as the 1950s.