Hail Characteristics in the Northwest Part of Croatia

Sa？etak Measuring and registration of hailstone parameters on the ground, because of their temporal and spatial variability and short duration, is very complicated. The necessity to obtain exact and objective hail data motivated the scientific community to construct and use a simple measuring device - hailpad. Installation of the measuring devices - hailpads on meteorological stations in the continental part of Croatia, as well as on the polygon in the northern region called ‘Croatian Zagorje’ in the year 2002, initiated measuring the exact physical parameters of hail in Croatia. This analysis presents measured physical characteristics of hail on the polygon for the time period 2002-2015. The measured values show that the highest hail parameters are recorded in June. Negative trend of relative frequencies of the smallest hailstones diameters (5.0-7.5 mm) is revealed and increase of the highest diameters (7.6-15.0 mm), which indicates possible increase of intensity of thunderstorms over the polygon’s area. Analysis of the hailstone spectrum showed that two-parametric gamma function is the best fit for the hailstones distribution on the ground. These results can be applied for assessment of possible hail damage based on calculation of kinetic energy or number of hailstones and intensity of damage on crop plants in their different phenophases development. For example, insurance companies can create more detailed risk maps of hail occurrence for particular area in order to have high-quality and objective hail damage assessment