Mesoscale meteorological features associated with heavy precipitation in the southern Alpine region

Several episodes of heavy precipitation, which occurred in the region south of the Alps, have been simulated by means of the mesoscale model BOLAM3. E ach case was run at 3 different resolutions, up to 4km grid interval. The q uantitative precipitation "forecast" fields are compared with available rai n data. In general, satisfactory results are obtained in terms of spatial d istribution and timing of precipitation, except in cases in which pre-front al convection is dominant. The diagnostics of phenomena involved in orograp hic precipitation identify the different mesoscale atmospheric features ass ociated with the interaction with topography, like the formation of low lev el jets, convergence zones, rainbands, and organized convective systems. Th ese appear as "ingredients" common to all the cases considered and are show n to be sensitive to orographic forcing, as well as to the latent heat exch ange processes.