drains primarily through the large eastern opening. 



111. This pattern can be explained by examination of the daily wind 

 pattern. The normal cycle during the study was an increasing breeze in the 

 morning clocking from north to east, with a rapid switch to westward around 

 midday (the sea breeze) and decreasing velocity after sunset (see Plate 54) . 

 These westerlies bracket the time from Higher Low to Higher High Water 

 (Figure 11). The wind shear would influence, and perhaps dominate, this 

 relatively weak flood stage- -at least at the surface. With this initial set, 

 the strong evening ebb from Higher High to Lower Low Water would tend to exit 

 the harbor eastward, even though the winds are lower. A previous current 

 measurement study conducted by NOAA in the summer shows similar trends (Smith 

 1989) . This flow pattern may not be observed at other times without this 

 relative phase relationship between the wind and tide. However, in a physical 

 model study conducted by WES in the early 1970 's that did not include wind 

 effects, the net easterly flow was evident during spring tide conditions, but 

 not at neap (McAnally 1975) . 



112. Another feature predicted by the physical model was a gyre in the 

 Los Angeles Harbor. Figure 8 provides some evidence of a counterclockwise 

 pattern occurring at the surface between 1800 and 2100 hr in the vicinity of 

 Station B, but the predominant pattern is the easterly flow in the outer har- 

 bor associated with ebb conditions. Winds during this interval were generally 

 blowing to the NNE between 5 and 10 knots, decreasing during the night. The 

 flow is less organized and weaker at middepth and bottom, though reversals are 

 evident in the water column. Low-velocity data from a profiling meter are in- 

 herently less reliable than an in situ meter because of the subjective averag- 

 ing by the operator over a shorter interval. There is some evidence that 

 rotational flow is occurring for short intervals, but not as a single, well- 

 defined gyre extending through the water column. Many more data points would 

 be required to characterize the flow pattern in the outer harbor more 

 completely. 



39 



