A numerical study of sea level and current responses to Hurricane Frederic using a coastal ocean model for the Gulf of Mexico

Abstract

A three-dimensional, nonlinear, primitive equation ocean general circulation model is used to study the response of the Gulf of Mexico to Hurricane Frederic. The model has free surface dynamics and a second order turbulence closure scheme for the mixed layer. Realistic coastlines, bottom topography and open boundary conditions are used in the study. The model has a vertical sigma coordinate with 18 levels, and a horizontal resolution of 0.2 ° × 0.2° for the entire Gulf. The study focuses on hurricane generated sea level, current, and coastally trapped wave (CTW) responses of the Gulf. Time series of sea levels from U.S. coastal tide gauge stations and the numerical model simulation of sea levels and currents on the shelf are used to study sea level, current and CTW responses. Both model sea levels and observations from tide gauge stations show a westward progression of the surge as a CTW response. The results of the study of sea levels and currents indicate that CTW propagate to the west with phase speeds of 7‐10 m s ‐1 . There is also a strong nonlinear interaction between the Loop Current and hurricane induced currents. The surface current attains a maximum of ~200 cm s ‐1 in the eastern Gulf. The model surface elevation at several locations is compared with tide gauge data. The current meter data at three moorings are also compared with the model currents. The model simulations show good agreement with observed data for the hurricane induced coastally trapped wave, storm surge, and current distribution in the Gulf.