Consistent tropical cyclone wind and wave forecasts for the U. S. Navy

A new algorithm to generate wave heights consistent with tropical cyclone official forecasts from the Joint Typhoon Warning Center (JTWC) has been developed. The process involves generating synthetic observations from the forecast track and 34, 50, and 64 kt wind radii. The JTWC estimate of maximum wind radius is used in the algorithm to generate observations for the forecast intensity (wind), and the JTWC estimated radius of outermost closed isobar is used to assign observations at the outermost extent of the tropical cyclone circulation. These observations are then interpolated to a high-resolution latitude-longitude grid covering the entire extent of the circulation. Finally, numerical weather prediction (NWP) model fields are obtained for each forecast time, the NWP model forecast tropical cyclone is removed from these fields, and the new JTWC vortex is inserted without blending zones between the vortex and the background. These modified fields are then used as input to the WAVEWATCH wave model to generate waves consistent with the JTWC forecasts. The algorithm is applied to several important events near Japan with mixed results. Overall performance of the new algorithm is dependent on the JTWC tropical cyclone forecast performance, which has generally outperformed those of the NWP model over the last several years.