GULF OF MEXICO 



Figure 7. Part of NOAA daily surface weather 

 map, 0700 e.s.t., 28 October 1976. 



Winds in the Gulf of Mexico during 17 August 1969 were due to Hurricane 

 Camille which passed almost directly over the gage. The track of the hurri- 

 cane center is shown in Figure 3. The center was 23 kilometers west of the 

 gage at its nearest point. The data record used in this study was collected 

 on an offshore platform as part of the oil industry's Ocean Data Gathering 

 Program. Patterson (1974) and Earle (1975) have reported on this unique data 

 record. The 60-minute sample selected for detailed analysis in this study 

 represents the highest energy wave conditions, recorded just prior to failure 

 of the gage. 



The data sample from the Oregon-Washington coast represents swell gener- 

 ated by circulation around a large low-pressure center located just south of 

 the Aleutian Islands (Fig. 8). The low-pressure center was fairly stationary 

 in this location for several days. Using the known swell period and the dis- 

 tance between the low and the gage (2,400 kilometers), the traveltime between 

 the two points can be estimated coarsely as 60 hours (U.S. Army, Corps of 

 Engineers, Coastal Engineering Research Center, 1977). Thus, the circulation 

 shown in Figure 8 for 1700 P.d.t., 14 October 1979, was almost certainly 

 responsible for generating the swell measured along the U.S. coast on 17 

 October 1979. Figure 9 shows evidence of a low-pressure system approaching 

 the measurement site but these local winds did not visibly affect waves until 

 after 1600 P.d.t. on 17 October. Many comparable swell episodes are probably 

 available from this gage. This particular episode was selected because it was 

 well documented as a result of another unrelated, unpublished study. 



The west coast data sample is least effective of the three field data sam- 

 ples in meeting desired criteria; the data were taken in relatively shallow 

 water compared with the other samples. The data are not continuous, waves are 

 not steep, and criteria (6) and (7) are unfulfilled. However, the waves are 

 expected to be very well focused in direction. The waves have been free from 

 direct wind action for a long time. Any fundamental instability operating on 

 the waves can be expected to have asserted itself after such a long time, a 



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