For example, a fast moving hurricane, which is generated inside the 

 Gulf might have an associated initial peak of tjq which is nearly in 

 phase with the primary shelf surge. 



A supplementary question addressed in the present study concerns 

 the surge behavior at the shelf break. This is at least as important 

 as the forerunner behavior for limited area models. In many 

 applications of surge models the domain of the model is limited to a 

 section of the continental shelf extending seaward from shore to the 

 shelf break (about 200 m depth) . A common boundary condition 

 employed in such limited area models is to set the water level (77) 

 equal to the local value of b for a given time during the traverse of 

 the hurricane through the model domain. The present study in which 

 the whole Gulf of Mexico (and part of the Cayman Sea) is modeled, 

 shows that the water level at the shelf break can depart 

 significantly from b at the shelf break. Moreover, this departure 

 (7?-b)g has a behavior differing from that of ijq and generally of 

 larger magnitude. For example, large scale (Rmax = 60 Ion) hurricane 

 simulations along PATH4 yield larger values of irj-h) ^ than do those 

 along PATHl; this is just the opposite behavior of tjq for these two 

 paths . 



In order to gain some further insight with respect to the shelf 

 break condition, three hurricane runs (HUR5, HUR23 and Car la) were 

 repeated with the winds turned off in the deep region of the Gulf and 

 Cayman Sea (i.e., for depths greater than H-j^) . This is equivalent to 

 having a limited area shelf model (including all shelves in the 

 system) but allowing wave energy to radiate into the deep Gulf. 



196 



