Long-term changes in the frequency and intensity of thunderstorms in Latvia

Thunderstorms are the most hazardous meteorological phenomena in the summer season in Latvia. However, so far not much has been known about the climatic characteristics of thunderstorm distribution and intensity in the country, and how these have changed with changing climate. Therefore, the aim of this study was to analyse the spatial and temporal distribution of thunderstorms in Latvia during the period 1960-2015 by using surface observation data from 14 major weather stations. To assess the severity of thunderstorms and suitability of the existing warning system, the frequency and distribution of thunderstorm intensities according to the national warning and hazard criteria was analysed. The results of our analysis show significant decrease in thunderstorm frequency in Latvia since 1960, however indicators of an increase in thunderstorm severity were also found, which reveals and emphasizes the complex nature of convective atmospheric phenomena also on climatic scales.