Remotely-sensed precipitation estimates and regional atmospheric model precipitation forecasts provide rainfall data at high spatial and temporal resolutions with a large-scale coverage, and can therefore be potentially used for hydrological applications for making flash flood forecasts and warnings. This study investigates the performance of the rainfall products obtained from the Hydro Estimator (HE) algorithm of NOAA/NESDIS and the Weather Research and Forecasting (WRF) model, and their use in a hydrological model (HEC-HMS) to simulate the catastrophic flood events which occurred in the Ayamama basin in northwest Turkey during 7-12 September 2009. The WRF model is also run with three-dimensional variational assimilation to obtain improved precipitation forecasts. The precipitation estimates at 4-km from the HE and WRF model, with and without assimilation, were evaluated against raingauge and radar data. The 4-km HE and WRF-estimated rainfall showed capabilities in capturing the timing of the flood events and to some extent the spatial distribution and magnitude of the heavy rainfall. Hydrological modelling based on HEC-HMS is applied using rainfall data from raingauges, radar, HE and WRF model. By use of surface hydrographs obtained from HEC-HMS, the HEC-RAS hydrological model is used to simulate inundation extent. The extent of the inundated areas in the river basin changes according to the peak discharges of the surface hydrographs used in the HEC-RAS module.