off Louisiana currents were to the north or east with the 

 northerly current generally restricted to nearshore waters 

 and the eastward movement restricted to the deeper 

 waters over the shelf. The strength of this eastward flow 

 was apparently greater in 1962 than in 1963 as evidenced 

 by the recovery of bottles as far away as Florida within 30 

 days after release. In 1963, bottles were also recovered in 

 Florida but time adrift exceeded 30 days and the 

 recoveries therefore are not shown in Figure 5. 



Current velocities varied throughout the study area 

 with values ranging from 3 to 12 km/day along the Texas 

 coast and averaging 7 km/day. Onshore currents along 

 the Louisiana coast ranged from 1 to 9 km/day with an 

 average of 3 km/day. Monthly velocities were similar be- 

 tween years. 



The influence of the prevailing southerly wind so char- 

 acteristic of the summer in the northwestern Gulf of 

 Mexico was readily apparent at Brownsville and 

 Galveston for June and July of both years. Surface water 

 currents off Texas were observed flowing either directly 

 downwind or slightly to the right of the prevailing wind 

 direction. Off Louisiana, however, the wind direction 

 varied between years. In 1962, air flow was to the east 

 whereas in 1963 it was more to the north. This variation 

 generally supports the stronger eastward movement of 

 surface waters off Louisiana in 1962. 



August. — Drift bottles were released during this time 

 period only in 1963, and their movements indicated still 

 another transitional period in current direction and 



velocity (Fig. 6). Surface currents, rather than moving 

 alongshore and to the north, had shifted to onshore 

 toward the west; velocities had slowed to a rate of 2-3 

 km/day, a marked decrease from those velocities 

 observed in the June-July period. 



At Brownsville and Galveston winds were generally 

 southeasterly. At New Orleans, winds were variable, as 

 evidenced by the relatively small resultant vector, and 

 were northwesterly. 



September-December. — The release and recovery of 

 drift bottles indicated that surface currents had returned 

 to the dominant flow noted in January-February, i.e., a 

 general west to southwesterly flow (Figs. 7, 8). Several 

 features of the circulation pattern, however, should be 

 noted. First, recoveries of bottles in the vicinity of 

 Brownsville, Texas, in 1962 indicated a westerly onshore 

 movement that dissipated as the season progressed. 



Second, the onshore component of the prevailing 

 southwest current was not as apparent in 1963 as in 1962. 

 Few bottles released in the study area were recovered 

 within 30 days, and of those that were, most were 

 released at nearshore stations. Whether this was due to 

 the lack of areal coverage or the total number of bottles 

 released is not known, but the results were similar to 

 those observed in December 1962 (Fig. 8), a period when 

 a large number of bottles were released and areal 

 coverage was extensive. This absence of recoveries may 

 indicate either an along- or offshore movement of surface 

 waters. 



BEAUFORTS 



Figure 6.— Surface circulation deduced from recoveries of drift bottles released in August 1963 in the northwestern Gulf of Mexico. (Arrows 



indicate direction of flow; numbers indicate average km/day). 



10 



