Tide-surge-wave modelling and forecasting in the Mediterranean Sea with focus on the Italian coast

A tide-surge-wave modelling system, called Kassandra, was developed for the Mediterranean Sea. It con- sists of a 3-D finite element hydrodynamic model (SHYFEM), including a tidal model and a third gener- ation finite element spectral wave model (WWMII) coupled to the hydrodynamic model. The numerical grid of the hydrodynamic and wave models covers the whole Mediterranean with variable resolution. The comparison with coastal tide gauge stations along the Italian peninsula results in a root sum square error for the main tidal components equal to 1.44 cm. The operational implementation of the Kassandra storm surge system through the use of a high resolution meteorological model chain (GFS, BOLAM, MOLOCH) allows accurate forecast of total water level and wave characteristics. The root mean square error for the first day of forecast is 5 cm for the total water level and 22 cm for the significant wave height. Sim- ulation results indicate that the use of a 3-D approach with a depth-varying loading factor and the inclu- sion of the non-linear interaction between tides and surge improve significantly the model performan in the Italian coast.