due to multimodal directional distributions where modes are widely separated. 

 This condition causes A^„ to become quite large. 



221. If the data are restricted to unimodal cases, the incidence of 

 broad spreads is reduced, as evidenced in Figure 28. Most of the directional 

 distributions are unimodal at the low frequencies (Figure 23) so the spread 

 distributions are little changed. At high frequencies, however, the effect of 

 eliminating multimodal distributions is to cause spread distributions to 

 become more like those at middle frequencies. The range of spreads is from 

 about 10 to 60 deg, and peaks in the distributions are in the range from about 

 35 to 40 deg. 



222. In summary. Figures 25 to 28 indicate that low- frequency wind 

 waves tend to arrive from the shore normal to slightly south of shore-normal 

 directions, and their directional distributions tend to be slightly narrower 

 than the bulk results of Figure 16. Ranges of peak direction and directional 

 spread tend to increase with increasing frequency. High-frequency wind waves 

 tend to arrive from anywhere on the (180-deg) horizon and, for full 180-deg 

 directional distributions, can have a characteristic spread of energy up to 



90 deg. Wave fields with unimodal directional distributions tend to display a 

 similar behavior in peak direction but a more uniform behavior of directional 

 spreads from frequency to frequency. Unidirectional wave fields are extremely 

 rare (in this data set) at any wind wave frequency. Overall, the directional 

 spread properties at each frequency, especially in the unimodal cases, is not 

 very different from the bulk properties shown in Figure 16, 



93 



