21+9 

 where D is travel distance, T^ is the period at the end of fetch, m is the 

 mean map factor, t is decay time, Tj is the swell period, H^ "the swell 

 height. H™ the height at end of fe'bch, and a-^ and b^ are ^constants. 

 Swell analyses and forecasts are plotted in the same manner as the waves in 

 Figure h. 



OCEAN CUREIENTS 



The details of this program have been described earlier by the author 

 (Hubert, 1964) . Essentially, the computational procedure accounts for two 

 principal current components -- (l) the "characteristic" or thermohaline 

 flow and (2) the mass transport due to wind and waves. 



Assuming a level of zero current velocity at some depth (Az) , the 

 geostrophic thermal current at the surface is computed from the mean tempera- 

 ture, T, in the layer 



g AZ 

 t = - = Vf X t" 



C f rp 



In practice, the mean temperature is obtained from a weighted combination 

 of a climatological temperature field at 200 meters and the synoptic SST 

 Analysis described earlier. 



The wind-driven current as determined by Witting (1909) is obtained 

 from 



^ = K3 ( f ) ^/^ 



w 3 g 

 where V is the mean geostrophic wind speed for a 36-hour period. 



Figure 5 is an example of a current transport chart (in nautical miles 

 per day) obtained at FNWF on a synoptic basis. As can be seen from this 

 figure, well-known features such as the Gulf Stream, Kuroshio, Equatorial 

 Counter Current, etc., are quite well defined by this procedure. Since the 

 computations are carried out in component (u,v) form, directional fields are 

 also available . 



In order to obtain a single continuous field displaying both direction 

 and speed of the computed currents, a stream function (i/;) analysis is made 

 using methods similar to those employed by Bedient and Vederman (1964) to 

 represent atmospheric flow in the tropics. The vorticity of the current flow 

 is determined from the (u,v) component fields and the Poisson equation 



V2^ = ll . 9£ 

 3x 9y 



is solved for \\) using relaxation techniques. 



