Some intense precipitation events are currently object of intensive study by means of numerical simulations in the framework of MAP (Mesoscale Alpine Program) Project. Among the others, the so called Vaison case, which occurred on September 22nd, 1992 has been selected for this work and the associated meteorological situation has been simulated using the Eta model. The flash flood associated with the intense precipitation resulted in serious damages, so that the correct meteorological forecast turns out to be of fundamental importance in order to try to reduce the dramatic impact of such episodes. This case seems to be a prototype intense rainfall event for the fall season in the Alpine Region. Nevertheless, several different numerical models are giving only partially successful representation of the episode, both in terms of the correct location and amplitude of the observed rainfall and of the actual chronology of the precipitation. The presence of a large amount of rain of convective origin due to the combination of several mesoscale convective systems in advance of a cold front crossing the French region during September 22nd seems to be one of the crucial aspects related to this failure. In this work, the results of Eta model simulations are presented, with a particular reference to the influence of initial conditions on the location of precipitation nuclei and to the simulated temperature and humidity fields with respect to the available observations and the ECMWF analysis
