Implementation of synoptic patterns to the Iberian Peninsula in autumn

The objective weather-type system of Synoptic Objective Processes (PSO) by Fernández y Díaz (2003), based on surface atmospheric pressure and 500 hPa topography according their temporal evolution along 3 days, has been applied to the Peninsular Spain and Balearic Islands. The advantages of this classification respect to the subjective ones and its capacity to reflect suitably the weather-types influencing over the study area in fall are exposed. The synoptic diversity of the area during the months of September and October are summarized by means of 20 PSOs. Their frequency and return period are calculated. The features of each PSO are put in relation with the probability of rain ant its daily mean amount.