[show abstract][hide abstract] ABSTRACT: A regional ocean forecasting system has been implemented in the framework of the ADRIatic sea integrated COastal areaS and river basin Management system Pilot Project (ADRICOSM). The system is composed of a 5 km horizontal resolution model and an observing system collecting coastal and open ocean hydrological data. The numerical model is based on the Princeton Ocean Model using a SMOLARKIEWICZ iterative advection scheme, interactive air-sea flux computation, Po and other Adriatic rivers flow rates and is one-way nested to a general circulation model of the Mediterranean Sea. In this study the data from the observing system are used only for model validation. The results of the first operational year are shown and the model performance has been assessed based on root mean square (RMS) criteria.