CR 71:91-109 (2016)  -  DOI: https://doi.org/10.3354/cr01432

ABSTRACT: Climatological analyses of hailstorms, as phenomena of local or regional occurrence with associated damage, depend strongly on the quality and density of meteorological observations. Documentary sources, both historical and modern, including insurance company records, can be used to complement existing meteorological data or extend them into the period prior to continuous meteorological observations. This paper employs such aids to compile a long-term hailstorm chronology for the summer half-year (April-September) in South Moravia (Czech Republic) based on derivations from various types of documentary evidence together with systematic meteorological records. Although the first single hailstorm record dates back to 17 August 1435, the number of hailstorms detected only increases significantly after the 18th century. Documentary sources favour reports of particularly damaging hailstorms, so frequency increases with the number of surviving documents; obviously, this can never achieve the coverage maintained in the period of organised meteorological observations. The best temporal coverage of hailstorm days during the summer half-year in South Moravia starts in 1925 and expresses an overall decreasing trend of -0.05 d per 10 yr up to 2015, more marked after 1961 (-1.4 d per 10 yr). Particularly damaging hailstorms, on 20 June 1848, 1 July 1902, 10 July 1902 and 19 July 1903, are described. Finally, uncertainties in the hailstorm chronology are discussed, and differences related to various aspects of hailstorm days detected from documentary and meteorological data in three 40 yr periods are analysed.

KEY WORDS: Hailstorms · Hailstorm days · Damaging hailstorms · Documentary data · Meteorological observations · Fluctuation · South Moravia