The development of an operational SWAN model for NGLI

Military operations levy increasing demands for wave forecasts well into the littoral regions and surf zone, and thus drive the need for high-resolution ocean surface wave models. This requires a specialized model that includes shallow-water physics and is stable at high resolution. SWAN (Simulating Waves Nearshore (Booij et al., 1999)) is one such model. Like the larger scale wave models used at the Naval Oceanographic Office (NAVOCEANO), SWAN is a "third-generation" numerical wave model and has no limitations on propagation direction. Input for SWAN typically consists of surface wind, wave spectra boundary conditions, and high-resolution bathymetry. SWAN provides the user a large span of configuration options to fit the needs of varied applications. This paper describes a real-time nowcast/forecast implementation of the SWAN model, designed and tested at the Naval Research Laboratory (NRL) and NAVOCEANO to support the Northern Gulf of Mexico Littoral Initiative (NGLI) Project. NGLI provides an ideal venue for model validation, as it includes an extensive observation system in predominantly shallow and intermediate-depth water. A variety of comparisons are made between SWAN output and in situ data within the NGLI region. Additionally, the accuracy of SWAN's forcing - derived from WAM (Wave Model) and COAMPS (Coupled Ocean/Atmosphere Mesoscale Prediction System) - needs to be evaluated, as does the impact of their accuracy on the SWAN model. Furthermore, logistical issues related to the introduction of this experimental modeling capability into military operations are being investigated and evaluated.