The climatology of supercell thunderstorms across Poland based on multisource data

Abstract

Each year supercell storms in Europe are responsible for significant property damage and cause injury and death to people. Storms that have a deep persistent rotating updraft are capable of generating particularly violent phenomena - flash floods, large hail and strong wind gusts of convective origin.Supercells are also responsible for producing the strongest tornadoes with intensity of even F4-F5 in Fujita scale as evidenced over the recent decades across Europe, including Poland. Despite significant hazards posed by these types of storms, no research on climatological aspects of supercell thunderstorms in Poland has been carried out so far. The goal of this work was to study spatial and temporal characteristics of supercell thunderstorms in Poland between 2008 and 2022. In order to accomplish this task, a vector-tabular database of supercell thunderstorms over Poland was created, based on a manual analysis of 10-minute interval radar data accompanied by severe weather reports from the European Severe Weather Database (ESWD). The typical radar-derived signatures of supercells (e.g. bounded weak echo region, velocity couplet, hook echo) and/or long, continuous paths of high radar reflectivity with deviant motion were one of the main identification criteria. Identified supercells were classified into 3 groups, based on the confidence of their detection from plausible events to those producing significant severe weather. Manual evaluation of 15 years of radar and ESWD data allowed to analyse in the climatological context supercells track widths and lengths, storm duration, spatiotemporal frequency, accompanying hazards and characteristics such as right- or left-moving movement propagation. Moreover, ERA5 reanalysis was used to study accompanying atmospheric environments of identified supercells. An addition of lightning data from the PERUN network enabled also to evaluate non-supercell storm environments to show differences with supercells.