Stastical Studies on Thunderstorm Situations in the Netherlands

Abstract

Records from a network of volunteer thunderstorm observers in the Netherlands are used with routine synoptic and upper-air data to investigate relations between storm severity and almost simultaneous (just prior) meteorological parameters. The latter are derived from fields of the meteorological variables. The ?2 test and screening regression show that the ratio of storm associated with lightning damage to the total number of storms increases significantly with the surface wet-bulb potential temperature (? sw) and the instability index (?T), but the relations are rather weak. Hail frequency increases monotonically with the instability index, but is bimodally distributed with respect to the potential temperature. Hailsize-windshear relations are barely significant. Additional information provided by parameter combination over that in a single best predictor is limited by fairly strong correlations between wind velocities at 700 and 500 mb as well as by correlations among the surface wet-bulb potential temperature, the stability index and the saturation deficit (D). Stratification of the data according to synoptic situation and the use of nonlinear functions of the variables improve some of the relations.