2. Numerical model 

 a) Grid system 



A space- staggered computational mesh is employed in the 

 numerical analogs of the normal mode equations (37) and (38). The 

 grid spacing is taken as 15' x 15' in latitude (A4>) and longitude 

 (A\) . The modal transport per unit width, represented by U, V for 

 east and north components, respectively, is located at the mid points 

 of the appropriate sides of each grid block. The modal water level 

 anomaly, 4/, is defined at the middle of each grid block. Figure 1 

 illustrates locations of these variables whose positions are 

 identified by I, J and time is indexed by n. The grid spacing is 

 taken as the distance between the same variables, thus consecutive U, 

 \|/ values are at half increments of I and consecutive V, i// values are 

 at half increments of J. The depth is stored at every variable 

 location . 



The grid system used in this study is the same as that used in 

 the Gulf of Mexico Tidal Model (Reid and Whitaker, 1981). It 

 nominally covers 70 x 50 grid blocks for the Gulf of Mexico and the 

 northwest portion of the Caribbean Sea (Cayman Sea) as shown in Fig. 

 2. 



The depths of the Gulf of Mexico were digitized from bathymetry 

 charts prepared by Buffler et al. (1984). The Cayman Sea depths were 

 taken from available hydrographic charts. Depth over most of the 

 Cayman, especially near the open boundaries to the east and south, 

 was taken as 4000 m. Figure 3 shows the computer plotted contours of 



17 



