Numerical Optimization and Validation of the Nearshore Wave Prediction System across the Tropical Atlantic Ocean Driven by the Official Tropcial Analysis and Forecast Branch/National Hurricane Center Gridded Wind Forecasts

The Nearshore Wave Prediction System (NWPS, Van der Westhuysen et al. 2013) has been configured and tested across the tropical Atlantic Ocean basin through the 2013 tropical season in experimental mode. Although this system was primarily designed to provide on-demand, high-resolution nearshore wave guidance consistent with the official National Digital Forecast Database (NDFD) winds locally produced at the coastal Weather Forecast Office (WFO) level, further investigation through a hindcast simulation of Hurricane Isaac (2012) and daily simulations at the National Hurricane Center's (NHC) Tropical Analysis and Forecast Branch (TAFB) over the course of the 2013 tropical season have proven applicable, even for basin-scale oceanic applications. The primary motivation attributed to this development is two-fold: to ensure consistency between the Tropical Cyclone Forecast Advisory (TCM) wind fields and wave heights forecasted by TAFB during tropical cyclone operations and to generate wave boundary conditions for the coastal WFOs running NWPS across a coastal domain within TAFB's Atlantic domain. Initializing each WFO's local wave model grid boundaries with the output of a coarser NHC-TAFB wave model run (forced by the official NHC wind forecast) will help achieve a seamless mosaic of digital marine forecasts between NHC-TAFB and coastal WFOs impacted during tropical cyclone events. This paper presents a description of the system design and purpose, along with the results of a validation period through the 2013 tropical season that compares the NWPS model results against: observations at 14 buoy stations across the Atlantic, Caribbean and Gulf of Mexico, WAVEWATCH III® (WW3) and the ECMWF-Wave models. The numerical modeling challenges faced under operational forecasting constraints and the limitations associated with the gridded TCM Wind fields that are used to force the wave model will be demonstrated through field cases. Future enhancements necessary to further optimize the system will also be discussed.

References:

Van der Westhuysen, A.J., R. Padilla, P. Santos, A. Gibbs, D. Gaer, T. Nicolini, S. Tjaden, E.-M. Devaliere, H.L. Tolman, 2013: Development and validation of the Nearshore Wave Prediction System. Proc. 93rd AMS Annual Meeting, Austin, TX.