National Deployment of the Nearshore Wave Prediction System for Marine Hazard Guidance

The need for high-resolution operational guidance on coastal marine hazards such as waves, rip currents and wave runup has been steadily increasing. To address this, the Nearshore Wave Prediction System (NWPS) has been implemented as an on-demand downscaling of the global WAVEWATCH III Multi_1 model on the National Weather Service’s (NWS) operational supercomputer. The initial implementation was for NWS’s Southern and Eastern Regions, and in Fall 2016 it will be expanded to full national coverage, including also Western, Alaska and Pacific (Hawaii and Guam) Regions. To ensure consistency in their marine forecasting, NWPS is driven by forecaster-developed wind grids compiled locally at coastal Weather Forecast Offices (WFOs). The model runs are configured in real time in the AWIPS forecaster interface, and then submitted to the central supercomputer, where it is processed by the spectral wind wave model SWAN. The simulation incorporates tidal and surge water levels from ESTOFS (extra-tropical conditions) and P-Surge (tropical conditions), and surface currents from RTOFS Global. In Alaskan waters, the system also incorporates ice fields from the daily NCEP sea ice concentration analysis. The forecast guidance provided by NWPS includes fields of bulk wave parameters (e.g. significant wave height, period and direction), as well as partitioned and tracked wave systems. In order to provide detailed guidance on marine hazards such as rip currents and wave runup, unstructured meshes are being developed for ten forecast offices around the country, which feature a resolution of 500 m or less along the inner coastal zone. Wave model outputs along shallow water contours are then used to drive empirical rip current and wave runup models at operationally viable computational times. The presentation will include examples of the operational products of this system, as well as regional and case-specific validation results.