Progress on the IOOS COMT Wave, Surge and Inundation Modeling Testbed for Puerto Rico and the US Virgin Islands

The operational modeling of storm surge and inundation in U.S. Caribbean and Pacific islands poses many challenges. Wind waves play a more dominant role in driving the storm surge in these steep, reef-fringed environments than for milder-sloped coastlines along the mainland. Since Puerto Rico and the U.S. Virgin Islands are frequented by hurricanes and are well-instrumented, it is an ideal region for model inter-comparison. This project, which forms part of U.S. IOOS’s Coastal and Ocean Modeling Testbed (COMT), aims to evaluate a number of coupled wave and surge models for potential operational implementation at NOAA’s National Hurricane Center and San Juan Weather Forecast Office. The coupled wave-surge models compared are ADCIRC-SWAN and SLOSH-SWAN, and additionally the unstructured version of WAVEWATCH III is tested. To assess infra-gravity waves over the fringing reef and onto the beach, the phase-resolving models BOSZ and FUNWAVE are compared. The field cases considered are Hurricane Georges (1998), Hurricane Irene (2011) and Superstorm Sandy (2012). The results show good skill in the prediction of surge levels and wave heights in the high-resolution, state-of-the-art ADCIRC-SWAN model, but at a high computational cost. By comparison, the simplified SLOSH-SWAN model shows generally comparable results at a lower computational cost, but is still prohibitively expensive for operational application. A number of sensitivity tests are discussed to show the influence of wind forcing, and physics and numerics settings. The phase-resolving models capture the infra-gravity band of the wind-wave spectrum, which is absent in the coupled phase-averaged models. An important operational outcome of this testbed is the production of Maximum Envelope of Water (MEOW) and Maximum of Maxima (MOM) fields over Puerto Rico, and the recommendation to implement a more efficient, simplified wave model for coupled surge calculations.