Change of Thunderstorms and Tornadoes

Abstract

In this chapter, on the basis of meteorological observation series from 47 meteorological stations for the years 1951–2018 and data from the Scientific Station of the Climatology Department of the Jagiellonian University in Kraków for the years 1901–2018, the analysis of the long-term variability and annual course of the thunderstorms occurrence in Poland was undertaken. The results of research on the occurrence of tornadoes in Poland for the years 1810–2018 were also presented, and the data used in the analysis come from the European Severe Weather Database (ESWD) and historical sources. Additionally, long-term changes in meteorological conditions leading to the occurrence of thunderstorms and tornadoes were identified. For this purpose data from the ERA5 reanalysis were used. The results obtained revealed that the period of thunderstorm activity during the year became longer than at the beginning of the periods under consideration and shifts towards the first months of the year. It was also found that in the period 1951–2018 in the eastern part of the country can observe signals of an increase in the frequency of days with thunderstorms, while in the western part trends are rather downward. However, long-term variability of the thunderstorms occurrence during the period of over 100 years does not indicate a clear tendency of changes and only in the cool season the trend is increasing and statistically significant. It was also determine that tornadoes are really rare phenomena, but always occurring in Poland. Each year, on average 5 weak tornadoes, 1–2 significant tornadoes (up to F4 in Fujita scale) and 4 waterspouts are reported. At the same time, it has been shown that with the ongoing climate change, environmental conditions are becoming consistently more conducive for severe convective phenomena occurrence in Poland.