Abstract.A coastal forecasting system was implemented to provide wind wave forecasts over the whole Mediterranean Sea area, and with the added capability to focus on selected coastal areas. The goal of the system was to achieve a representation of the small-scale coastal processes influencing the propagation of waves towards the coasts. The system was based on a chain of nested wave models and adopted the WAve Model (WAM) to analyse the large-scale, deep-sea propagation of waves; and the Simulating WAves Nearshore (SWAN) to simulate waves in key coastal areas. Regional intermediate-scale WAM grids were introduced to bridge the gap between the large-scale and each coastal area. Even applying two consecutive nestings (Mediterranean grid → regional grid → coastal grid), a very high resolution was still required for the large scale WAM implementation in order to get a final resolution of about 400 m on the shores. In this study three regional areas in the Tyrrhenian Sea were selected, with a single coastal area embedded in each of them. The number of regional and coastal grids in the system could easily be modified without significantly affecting the efficiency of the system. The coastal system was tested in three Italian coastal regions in order to optimize the numerical parameters and to check the results in orographically complex zones for which wave records were available. Fifteen storm events in the period 2004-2009 were considered.

Abstract. The coupling of a suite of meteorological limited area models with a wave prediction system based on the nesting of different wave models provides for medium-range sea state forecasts at the Mediterranean, regional and coastal scale. The new system has been operational at ISPRA since September 2012, after the upgrade of both the meteorological BOLAM model and large-scale marine components of the original SIMM forecasting system and the implementation of the new regional and coastal (WAM-SWAN coupling) chain of models. The coastal system is composed of nine regional-scale high-resolution grids, covering all Italian seas and six coastal grids at very high resolution, capable of accounting for the effects of the interaction between the incoming waves and the bathymetry. A preliminary analysis of the performance of the system is discussed here focusing on the ability of the system to simulate the mean features of the wave climate at the regional and sub-regional scale. The results refer to two different verification studies. The first is the comparison of the directional distribution of almost one year of wave forecasts against the known wave climate in northwestern Sardinia and central Adriatic Sea. The second is a sensitivity test on the effect on wave forecasts of the spatial resolution of the wind forcing, being the comparison between wave forecast and buoy data at two locations in the northern Adriatic and Ligurian Sea during several storm episodes in the period autumn 2012-winter 2013.

The Mediterranean Coastal Wave Forecasting (MCWAF) system has been operational at the Italian National Institute for Environmental Protection and Research (ISPRA) since September 2012. The principal aim of the system is to provide medium-range wind-generated wave forecasts for the Mediterranean on a regional and coastal scale. The detailed information about the sea state near the shore also allows the use of the results to be applied to coastal investigations related to the wave climatefor example, making estimates of wave power and identifying biological habitats.

This paper describes a research aimed at developing a high-resolution nearshore wave forecasting/hindcasting system for the Italian coasts. Data recorded by buoys located in shallow water are compared with hindcasted data. The model uses the results of the well-tested large scale meteorological forecasting system named 'Idro-meteo-mare' (SIMM) managed by ISPRA, the Italian Agency for the Environmental Protection and Research, as wind input for WAM and SWAN models. Two different approaches are used for the Adriatic and the Tyrrhenian/Ligurian Sea. In the first eastern basin two/three SWAN nested grids have been used, while in the second western basins two WAM nested grids and a finer SWAN grid have been used. Both methodologies have shown a good accuracy and and a reasonable level of efficiency.