forcing is available for hurricane Allen than for hurriccUie Carla. 



Hydrographs from the Mexican stations {Figs. 44-46, p. 89 - 91) 

 reveal almost no response except for tjq for the entire period 

 considered. The computed water level at Progreso shows a response to 

 the barometric pressure drop during the passage of the center of 

 Allen between 1800 GMT 7 August to 0006 GMT 8 August. However, the 

 observed hydrographs have no indication of this perturbation. This 

 circumstance also occurs in the simulation of hurricane Carla (cf . 

 Fig. 28, p. 70). It is not yet appreciated why the Mexican coast is 

 passive to these two hurricanes. 



The slow oscillation found at Key West and St. Petersburg in the 

 Carla simulation is also present. It is noticeable again at all 

 stations from Key West to Appalachicola . 



The maximum computed water level occurs at grid point (4,33) 

 which is the location of the sample point for the Port Isabel 

 hydrograph. This simulated peak surge is of the order of one meter 

 higher than the recorded peak. This is to be expected considering 

 the difference in locations of the simulated and actual hydrographs 

 (cf. Fig. 29, p. 72). In addition to reduction of the magnitude of 

 wind speed at the actual tide station by South Padre Island, the 

 volume responses inside the Laguna Madre will be small because of the 

 constricted opening. These factors contribute to a higher computed 

 water level at this station. A slower retreat in the observed 

 hydrograph is due possibly to the trapping of water inside the 

 embayment . 



92 



