Improving hail identification in the Ebro Valley region using radar observations: Probability equations and warning thresholds

In order to identify hail into thunderstorms identified with radar data, different kinds of techniques are use based. This paper will evaluate some of these methodologies for the case of the Ebro valley (NE Spain), in order to obtain the best method to identify hail at surface. To achieve this end, an analysis of the 2004 and 2005 hail seasons has been undertaken using C-band radar, MM5 meteorological model outputs and ground observations provided by two hailpad networks. These data were integrated, identifying, characterizing and tracking the convective cells, and obtaining for each one different hail probability equations by means of various radar techniques. Kinetic energy flux was found to be the best parameter for distinguishing between hail and no-hail precipitation, although there was found to exist no significant difference between the various methods used. Moreover, the high correlations between radar parameters obtained by means of cell analyses led us to reduce the initial number of variables in new radar parameters. These new variables are defined and provide new improved models of the intensity of the storm.