A case of unpredicted deep convection on the Sardinia Island (Tyrrhenian sea) is analyzed. Sensitivity to the improved Initial Conditions using 3DVAR to assimilate conventional, and both GPS and SSMI PW data is performed. Model simulations are carried out using MM5V3 and WRF: the first one at high resolution (1km), whereas the second one at coarse resolution (27km); both models are initialized by using the improved Initial Conditions. WRF is used to verify its ability to overcome the well known MM5 shortcomings to underestimate the rainfall at coarse resolution. The observed rainfall is used to validate both models results.