A COMPARATIVE-STUDY BETWEEN 2 CASES OF EXTREME RAINFALL EVENTS IN CATALONIA

A diagnostic study of the synoptic aspects of two cases of heavy rain producing floods in Catalonia (northeast corner of the Iberian peninsu la) is presented. The diagnosis consists in the determination of the a rea where large scale circulation induces favorable conditions for dev elopment of thunderstorms. We identify these conditions as upward quas i-geostrophic forcing, convergence of water vapor at low levels and co nvective instability in the lower troposphere. A composite chart showi ng where the three synoptic mechanisms overlap determines the area. Lo cal studies of instability are carried out from upper air data given b y the radiosonde ascents of Palma de Mallorca, looking for both the Co nvective Available Potential Energy and Bulk Richardson number and its temporal evolution during the events.