The operational forecast for IOP2b showed failure in reproducing the rainfall. During the campaign a larger amount of data than the usual operational one was recorded. These data are at higher space and time resolution. An analysis of the impact of the increased resolution both in space and time is performed. A new set of mesoscale Initial and Boundary conditions are generated by assimilating the data using Objective Analysis and ECMWF data analysis as First Guess. Sensitivity to the enhanced data resolution is performed using the MM5V3 and the results are compared with both a simulation performed without using assimilation and the observations.