engleski

Testing waterspout forecasting indices over the Adriatic sea using ALADIN model

Waterspouts are severe mesoscale phenomena that can cause great damage to lives and property. Many waterspout events have been recorded in Croatia over the past several years, especially during the summer months. This motivated us to test and develop some forecasting tools that will help forecast waterspout events. Two forecasting indices are most often cited in the literature: the Szilagyi Waterspout Index (SWI) and KHS – Index to calculate risk of (water)spout development. For the SWI a combination of three parameters correlates strongly with waterspout events: difference between water temperature – 850 mb air temperature, convective cloud depth and 850 mb wind speed. The KHS index is based on four parameters: vertical wind shear 0-3 km, 0-500 m lapse-rate, average humidity in the first kilometer and 10 m wind speed. In this study we test these two indices on several case studies. The SWI and KHS are calculated from the Aladin model used operationally in the MHS of Croatia. During the 2010 19 days with waterspouts observed along the Adriatic coast were identified. For all 19 events short description about time, location, synoptic situation (weather type and thermodynamic environment) is given as well as yes/no for the value of both indices. Results of a detail analysis of 4 waterspout events are presented. The research shows that most of the waterspout events were thunderstorm related ; however, for those that are not (fair-weather) more than just common thermodynamic instability indices are needed. Our study shows that SWI and KHS indices improve the waterspout forecast.

waterspouts; forecast indices; ALADIN

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