VALIDATION OF THE NEARSHORE WAVE PREDICTION SYSTEM FORCED BY GRIDDED TROPICAL CYCLONE WINDS
Alex Gibbs, Pablo Santos, Andre van der Westhuysen, and Roberto Padilla-Hernandez
Recent code enhancements to the National Weather Service (NWS) Tropical Cyclone Wind Tool (TCWT) based on a Collaborative Science, Technology, and Applied Research (CSTAR) project between North Carolina State University and several National Weather Service (NWS) forecast sites provide forecasters a larger degree of flexibility to further refine gridded wind forecasts associated with tropical cyclones through several new techniques that have stemmed from recent research. The TCWT is based on the modified Rankine Vortex algorithm and is used by NWS offices to insert the tropical cyclone vortex within their official wind grids. Some of the recent code enhancements (Santos et al., 2014) include: 34, 50, and 64 knot wind radii adjustments based on multi-regression bias correction equations described by DeMaria et al., 2009, the ability to account for asymmetric tropical cyclones while preserving maximum winds in the inner core, and the ability to use wind reduction factor grids to account for spatially varying land friction induced wind reduction.
The centrally ran Nearshore Wave Prediction System (NWPS-WCOSS, Van der Westhuysen et al. 2016) uses TCWT derived wind grids from each coastal forecast office within the NWS as input forcing. Previous limitations derived from the legacy TCWT introduced significant challenges when used to force the NWPS. Overestimated wind fields derived from the tool would be reflected in the wave model results and would often translate to unrealistically high biases.
The main objective of this paper is to test the following hypothesis: recent advancements to the TCWT support more accurate wave model results. This is tested through evaluation of several field cases that compare the NWPS results between the legacy TCWT and the improved TCWT against real-time observations from nearby buoy stations.
DeMaria, M., J. A. Knaff, R. Knabb, C. Lauer, C. R. Sampson, and R. T. DeMaria, 2009: A new method for estimating tropical cyclone wind speed probabilities. Wea. Forecasting, 24, 15731591.
Santos, P., C. Mattock, J. Lewitsky, and J. A. Gibbs, 2014: TCMWindTool Versus Gridded TCM. Presented at the 2014 NOAA Hurricane Conference. [https://drive.google.com/a/noaa.gov/file/d/0B1Oi6uAD-Z9xOFdhOURxX1JKeFU/view]
Van der Westhuysen, A.J., R. Padilla, P. Santos, A. Gibbs, D. Gaer, G. Dusek, J. Long, H. Stockdon, J. Notchey, and H.L. Tolman, 2016: Implementing the Nearshore Wave Prediction System as a centralized, on-demand marine hazard guidance system. Proc. 96th AMS Annual Meeting, New Orleans, LA.