THE ENVIRONMENTS OF SIGNIFICANT CONVECTIVE EVENTS IN THE WESTERN MEDITERRANEAN

The environmental characteristics associated with 313 significant conv ective events in the western Mediterranean are investigated using radi osonde ascents made in Mallorca (Spain). The events are separated into five groups, based on the observed event (hail, heavy rain, ''dry'' s torms, storms with heavy rain, and tornadoes). Classic stability indic es, as well as values of convective available potential energy and hel icity, are considered for each group. These traditional convective ind ices appear not to provide good guidance for discriminating environmen ts associated with each group of events. In order to classify the envi ronments, each sounding is defined by means of 34 variables that descr ibe the thermal and humidity vertical structure, instability, precipit able water, and helicity. A cluster analysis shows that four different vertical structures appear, Each kind of event shows preference for t he environments defined by a cluster. A simple method is presented for sounding classification using the four categories obtained from the c luster analysis, The method looks for the best correlation between a p articular sounding and those defined by each cluster.