SHELF-SEA RESPONSE TO TROPICAL STORMS ALONG THE WEST-COAST OF MEXICO

The shelf-sea response to tropical storms along the west coast of Mexico is investigated using a layered ocean model forced by a travelling circular storm. Simulations using a straight coastline with a narrow continental shelf show that the response is typified by a cyclonic eddy along the storm track with inertial oscillations in the deep ocean and a trapped wave pulse at the coast. The coastal wave has typical phase speeds of 1.5-2. 0 m s-1, alongshore scales of 500-1000 km, and cross-shore scales of 100-200 km. Test runs indicate that the coastal response is a function primarily of the intensity and duration of alongshore winds near the coast, and of the propagation speed of the storm relative to the free coastal-trapped wave phase speed. Atmospheric pressure anomalies appear to play a minor role in generating the coastal wave. Model runs using realistic bathymetry and storm parameters for two hurricanes during the summer of 1984 are compared with current, temperature and pressure observations in the Gulf of California. The model results are in good agreement with observed wave properties with typical surface displacements of 20 cm, alongshore current speeds of 0.5 m s-1, and upper interface displacements of 30 m. Wave generation for the two 1984 storms occurs primarily in the vicinity of Cabo Corrientes where storm winds are reported to be the strongest. The cape geometry in this region may also contribute to the enhanced response.