Comparison of the rj^ (i.e., at the shelf break) from these runs with 

 their counterparts for the fully forced model shows that there 

 remains a significant difference (of order of 0.4 m) in the peak 

 values . 



The primary conclusions of this study can be summarized as 

 follows: 



(1) The surge on the shelf including the forerunner 



is primarily a barotropic response; very little of the 

 baroclinic energy generated within the deep water regions is 

 transmitted onto the shelf . 



(2) The forerunner, when it occurs, is associated primarily 

 with the Gulf -wide modes contained in t}q (the spatial 

 average of the Gulf water level at a given time); this is a 

 volume mode which exhibits periods of about 28 hours and 3.4 

 days. 



(3) Forerunners are always associated with tjq, but not all 

 hurricanes which excite tjq have an associated forerunner. 

 Regardless of whether or not forerunners exist, tjq can, if 

 properly phased, affect the magnitude of the pesik surge. 



(4) Limited area shelf models (at least within the Gulf of 

 Mexico), which enploy the seaward boundary condition tj = b 

 (or the generalization of this which allows outward 

 radiation of free waves) will always underestimate the peeik 

 surge at shore; the underestimate can amount to as much as 

 10 percent. 



197 



