Effect of wind resolution on spectral wave modeling in the Hawaii region

Abstract

Hawaii is affected by wind waves and swells throughout the year. The wave conditions are currently provided by four NDBC deep-water buoys in the open ocean and three UH near shore buoys as well as the third generation spectral wave (WW3) model operated by NOAA at the global level. This study examines the implementation of a high-resolution regional WW3 model to supplement the existing data in Hawaii. The global WW3 model is replicated at UH to provide spectral boundary conditions for the Hawaii domain, which covers the six major islands of the state at 3-minute resolution. The use of interpolated Global Forecast System (GFS) winds as well as fifth generation mesoscale model (MM5) winds as input is examined. Two case studies of approximately two weeks long each are chosen based on the local wind and global wave characteristics. These events have a range of wind speeds, ground swells, and wind waves. Comparisons of the wind fields with satellite data shows that the interpolated GFS winds are not able to pick up the small scale wind perturbations and localized wind patterns created by the island's steep topography. A wave analysis quantifies the difference between Hawaii WW3 results obtained with interpolated GFS and MMS as the forcing. Since the local trade winds can generate strong swells, an adequate wind field is needed to drive the Hawaii WW3 model. These procedures to hindcast wave events can be implemented to forecast waves in the future and provide Hawaii with detailed wave data.