The principal objective of the European Project FLASH (Observations, Analysis and Modeling of Lightning Activity in Thunderstorms, for use in Short Term Forecasting of Flash Floods) is the improvement of flash flood forecasting. With this aim, the Spanish contribution is centred in the integration of radar and raingauge data, lightning data and MM5 outputs into the hydrological model RIBS (Real-time Interactive Basin Simulator). Eleven case studies which affected the coastal region of Catalonia, between 2000 and 2006, have been selected. This region is characterized by great vulnerability due to concentration of the major part of the population, tourism and agricultural activities. This contribution shows the data and methodology as well as some preliminary results obtained within the project.