MESOSCALE MODEL SIMULATIONS OF 3 HEAVY PRECIPITATION EVENTS IN THE WESTERN MEDITERRANEAN REGION

A mesoscale numerical model with parameterized moist convection is app lied to three cases involving heavy rainfall in the western Mediterran ean region. Forecast precipitation fields, although not perfect when c ompared to the observations of rainfall, appear to have sufficient inf ormation to be considered useful forecasting guidance. The results ill ustrate that a good simulation for this type of event in a region with complex topography is strongly dependent on a good initialization and prediction of the low-level flow and water vapor distribution. For tw o of the cases that have a marked synoptic-scale contribution, the sim ulations give reasonably accurate predictions of the precipitation dis tribution, although the amounts are generally underestimated. The thir d case exhibits relatively subtle synaptic-scale forcing and is domina ted by isolated convective storms (mostly over the sea) that also prod uced severe thunderstorms (including tornadoes), and the prediction of precipitation is not as promising. Overall, the results are encouragi ng in terms of potential application of mesoscale models operationally in the western Mediterranean region. Additional experiments beyond th e ''control'' simulations have been performed to isolate the influence of orography and water vapor flux from the Mediterranean Sea on the m odel simulations. This factor separation indicates that both effects c an be important contributors to a successful forecast. Suggestions are offered for future efforts in pursuing the application of mesoscale m odels to this forecast problem.