The origin and course of severe thunderstorm outbreaks in Poland on 10 and 11 August, 2017

Abstract This study documents the evolution of severe thunderstorm outbreaks that occurred on 10 and 11 August, 2017 in Poland. This study used cloud-to-ground lightning-strike data from the PERUN lightning detection network managed by the Polish Institute of Meteorology and Water Management – National Research Institute. In the description of storm phenomena the authors also applied synoptic maps, meteorological radar data, vertical atmosphere soundings and meteorological data from the station in Poland. The aim of this study was to trace the causes of the upward movement of supercells including the Mesoscale Convective System day by day, and to examine relationships between lighting distributions on 10 and 11 August, 2017. In Poland, on August 10, 2017, 154,524 cloud-to-ground flashes (CG) occurred, and 56,510 CG flashes the next day. On August 10, around 18% of all flashes had a positive current, but 29% the next day. The spatial distribution of the lightning in Poland was computed for 10×10-km grid cells. Based on the map analysis it was found that on those two days most of the positive flashes occurred in Greater Poland and Kuyavian-Pomeranian voivodeships, as well as on the border of Opolskie and Lower Silesia.