6-hr duration). The solid curves represent the distribution for the NWS data 

 (see Figure 19). The Puffin Island data follow the NWS distribution closely 

 in the lower parts of the curves. This is the region where the Puffin Island 

 data are most reliable. This implies that the NWS wind data are a good esti- 

 mate of the Puffin Island wind conditions which would give a good estimate of 

 the open water conditions in St. Paul Harbor and Chiniak Bay at Kodiak. The 

 following section presents the extremal analysis of the winds using the NWS 

 wind data. The extremal curves are recommended for design purposes. 



Analysis of Annual Maxima for NWS Data 



46. The NWS data for 1-, 3-, 6-, 8-, 10-, 12-, 15-, 18-, 21-, 24-, 27-, 

 and 30-hr wind speed averages were searched for yearly maxima for input to the 

 extremal plotting routine, EXPLOT. The resulting plots are provided in Appen- 

 dix C. It is apparent for all but the 1-hr averages that the smaller eight 

 data points have been smoothed out and can no longer be considered extremes. 

 For this reason the points in question were not used when fitting the least 

 squares lines to the data, and therefore, do not affect the resulting extrap- 

 olated wind speeds. Table 18 contains a full listing of the predicted wind 

 speeds for given return periods and hourly averages. The analysis was com- 

 puted for all directions, the offshore exposure (45-180 deg relative to deg 

 from North) and Womens Bay (202.5-247.5 deg) separately as indicated in Appen- 

 dix C and Table 18. The Extremal Type I or Fisher-Tippett I distribution was 

 used in this analysis. The Fisher-Tippett or Extremal Type II distribution 

 results were also computed and found to be unsatisfactory. In general, the 

 chosen extremal model fits the data very well as is demonstrated by the 

 plots. 



Wave Forecasts Based on NWS Wind Data 



47. The long-term (extremal) distributions of wind velocities averaged 

 over varying durations for all directions for 247.5-292.5 deg (Womens Bay), 

 and for 45-157.5 deg (Gulf of Alaska) are presented in Appendix C. This in- 

 formation can be used to derive equivalent significant wave heights and peak 

 spectral periods, given appropriate assumptions of water depth and fetch. 

 Two sectors of interest were defined which correspond to the 7-mile fetch of 



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