scale and intensity, and to a lesser extent on the translational 

 speed of the hurricane. In general, the tjq during the first few days 

 after the hurricane enters the Gulf consists of three components. 

 The first two components (i.e., the Helmholtz mode and the 3.4 day 

 Gulf-Cayman mode) are associated with the volume transport through 

 the ports. The third component is a directly forced response 

 associated with the spatial average value of b (the inverted 

 barometer term) over the Gulf. PATHl tends to give the largest peak 

 7?Q, particularly for larger radius storms (compare HURl and HUR4 

 results) . 



Results from the limited area model and the full model disclose 

 that both the central pressure deficit and the wind induced 

 transports through the ports can excite the Helmholtz mode. However, 

 the relative importance of the two forcing fields in generating tiq 

 depends upon the storms' paths and their evolution. The almost 

 identical tjq obtained from the full and limited area models of 

 hurricane Car la and HUR23 show that the atmospheric pressure gradient 

 through Yucatan Strait was more important in the generation of rj^ 

 than the wind forcing. In contrast, the small Vq response in the 

 absence of wind in deep water for HUR5(L) implies that in this case 

 wind forcing was the major factor in generating tjq. 



The average periods of the Helmholtz mode from this study are in 

 the range of 25-32 hours. Platzman (1972) obtained a free Helmholtz 

 mode with a period of only 21.2 hours. This difference in periods is 

 due to the fact that r?G is composed of both forced and free 

 components. The average period of 28 hours obtained from the 21 day 



194 



