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20. ABSTRACT (Continued). 



variable bathymetry and variable Coriolis parameter. The model domain in- 

 cludes the Gulf of Mexico and the Cayman Sea with a resolution of 15'. A no- 

 flow condition is taken at all solid boundaries and the inverted barometer 

 term is used to stipulate barotropic height anomalies on the open boundaries. 

 Hurricanes Carla (1961) and Allen (1980) are used as historical storms to 

 verify the model by comparing numerical and observed hydrographs. 



A parametric study utilizing three forward speeds, two radii to maximum 

 winds, and five paths characterizing Gulf hurricanes is presented. The 

 results of the study show that volume transports through Florida and Yucatan 

 Straits consisted of in-phase (both in or both out) and out-of -phase com- 

 ponents. The in-phase volume transport excites a volume mode, t]q , in the 

 Gulf of Mexico having periods of about 28 h and 3. A days. The t\q mode of 

 oscillation can produce a forerunner surge for many storm tracks. Although 

 all the model storms generated Hq , not all had an associated positive 

 forerunner. The hurricane path and evolution play important roles in gener- 

 ating a forerunner. 



The out-of-phase volume transport through the ports was found to produce 

 a Gulf-wide quasi-geostrophic tilt mode of about 6.5-day period. Surges 

 on the shelf including the forerunner are primarily a barotropic response. 

 The quasi-linear model transmitted only a fraction of the baroclinic energy 

 onto the shelf. 



Results of a limited area model (no wind in deep water) showed that 

 either wind or pressure forcing generates ng . The limited area model 

 simulations also demonstrate clearly that the use of a simple inverted 

 barometer boundary condition at the shelf break will always underestimate 

 the peak surge at the coast. 



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