Observed versus forecasted precipitation in the South East Alps

Intense precipitation events are common on the SE slopes of the Alps and th e climatological maximum of precipitation is located in the area of the Jul ian and Carnic Alps. Mesoscale intensification of rainfall in the area is e xplained. Two cases of intense precipitation were studied with fine mesh me someteorological modelling using the ALADIN-SI model and verifying its resu lts with all available ground-based raingauge measurements. For the first c ase of 5-8 November 1997 mesoscale topographically induced direct lifting w as the main reason for precipitation intensification in the area. For the s econd case of 3-5 November 1998 this forcing was further modified by a meso front moving along the eastern edge of the Alps in the opposite direction t o the Row at upper levels. In the predicted precipitation the: most noticea ble feature was the shift of the forecasted precipitation fields by some 20 km with respect to the measured one leading to overestimation at the SW si de, and underestimation at the NE side of the mountain ridge. The role of d iscrepancy sources of differences between the forecasted and raingauge prec ipitation are evaluated.