1000 



1200 



1400 



1600 



Time 



Figure 6. Time history of significant wave height and peak spectral 

 period (from band spectrum with nine frequencies per band 

 and 0.0110 hertz bandwidth), South Pass, 17 August 1969. 



band spectra formed by combining variance from a fixed number of adjacent 

 analysis frequencies (see Thompson, 1977, for a more detailed description). 

 Data from Lake Michigan and the Gulf of Mexico fit the above criteria remark- 

 ably well, except for criterion (6). The Lake Michigan data also fall short 

 of criterion (7). In fact, it is questionable whether any data sets in the 

 United States meet all specifications. 



Meteorological conditions responsible for generating waves in the three 

 samples were quite different. National Oceanic and Atmospheric Administra- 

 tion's (NOAA) Environmental Data and Information Service daily surface weather 

 maps indicated that winds over Lake Michigan on 28 October 1976 were from the 

 south and southwest in response to circulation around a large high-pressure 

 center over Kentucky and southern Illinois (Fig. 7). Although the meteoro- 

 logical condition was not particularly severe, the gage happened to be in a 

 continuous recording mode during the episode. The gage signal had consider- 

 able noise contamination during the entire operation at the South Haven site, 

 but a 60-minute sample with relatively little noise was identified for this 

 study. 



24 



