SURFACE SYNOPTIC CIRCULATION AND DAILY PRECIPITATION IN CATALONIA

Catalonian daily precipitation patterns were obtained by means of S-mo de Principal Component Analysis (PCA) applied to subsets built up acco rding to synoptic surface airflow. Daily data from November to April 1 990-1994 from 45 raingauge sites in Catalonia without missing data wer e used. Eight circulation classes for days in this period were conside red. A Precipitation Activity Index (PAI) was calculated for each stat ion and class, leading to the determination of the highest activity re gions for each subset. In addition, we determined which circulation ty pe produced most precipitation at each station of the network. Separat e PCAs were performed for each of the eight classes considered and the first four Varimax rotated solutions were interpreted for each circul ation type. The physical meaning of the rest of the factors were omitt ed as they were associated with local behaviour. Finally, some conclud ing remarks on the cyclogenic properties of the Western Mediterranean Basin and the diversity of the extracted patterns are presented and su pported by the authors experience in forecasting in Catalonia.