FOREWORD 



This study was conducted by the Department of Oceanography at Texas A&M 

 University, Reference 85-2-T. The research was conducted through Texas A&M 

 Research Foundation Project 4667. 



This study was motivated by the fact that existing storm surge models 

 which are generally restricted to a limited reach of the continental shelf 

 do not adequately simulate the forerunner surge. In the Gulf of Mexico the 

 forerunner stage of a surge event (which can have an amplitude as large as 

 1 m) can precede the peak surge by more than 24 hours. 



It is common practice, in employing coastal surge models for design 

 purposes, to start computations with an initial non-zero constant water 

 level field over the shelf in recognition of the influence of forerunners. 

 This procedure makes no allowance for initial flows or gradient thereof 

 which must exist during the forerunner stage. On the other hand, starting 

 local coastal models well in advance of the arrival of the hurricane at the 

 shelf break cannot simulate the forerunner surge since the latter is ex- 

 cited by mechanisms acting over the adjacent deep basin seaward of the 

 coastal zone being modeled. 



The objectives of this research were to determine for the Gulf of 

 Mexico the space and time scales of forerunners, examine possible excita- 

 tion processes, and evaluate the role of baroclinic modes in surge events 

 at the coast and shelf break. A numerical approach was used in this study 

 which modeled hurricane-forced responses of the barotropic and first baro- 

 clinic modes over a computing domain representing the Northwest Cayman Sea 

 and Gulf of Mexico. The inclusion of the baroclinic response adds a degree 

 of realism lacking in previous studies on hurricane effects in the Gulf of 

 Mexico. 



