Similarly, in Runs 4 and 5 (Figs. 19 and 20), spectral energy values Increased 

 during those runs due to the favorable relative headings. During Run 6 (Fig. 21), 

 peaks definitely shifted to lower period values, reflecting the low period wave values 

 at the surface. 



V. SUMMARY OF RESULTS 



Table 4 compares values derived from the measured surface wave height spectrum 

 to similar values obtained by the hindcasting methods outlined in H. O. Pub. No. 

 603. Significant wave heights obtained by hindcasting are lower than values obtained 

 from the measured digital wave spectra. In addition, the highest periods from hind- 

 casting are 7.8 to 8.8 seconds while the highest periods from the measured spectra are 

 12.0 to 14.4 seconds. Wind speeds are plotted on the Northern Hemisphere synoptic 

 sea-level maps in increments of 5 nautical miles per hour. For fully-developed condi- 

 tions, a significant wave height of 3.2 feet and a wave period band of 1 .5 to 7.8^ 

 seconds occur when the wind speed is 14 knots; at 18 knots (fully developed) a signifi- 

 cant wave height of 6.1 feet and wave period band of 2.5 to 10.0 seconds would occur, 

 Thus, a 4-knot increase in wind speed (an increase of about 5 miles per hour) results in 

 a significant wave height increase of 3 feet and an increase of 2.2 seconds at the high 

 end of the wave-period band. In addition, high period swell of very low amplitude 

 from many different sources, whose contribution could be detected in a measured wave 

 spectrum, could never be hindcasted from the present oceanic weather maps. Thus, 

 data presented in Table 4, from two different sources, appear to be fairly consistent. 



TABLE 4. SUMMARY OF RESULTS DERIVED FROM SURFACE WAVE SPECTRA 

 (DIGITAL) AND COMPARISON TO HINDCAST WAVE DATA 



Run 

 No. 



Values from the Measured 

 Wave .Spectra 



H 



1/3 

 (Ft) 



T-Band 

 (Sec) 



Values from HIndcast 

 Wnye Data 



H 



1/3 

 (Ft) 



T-Band 

 (Sec) 



4-2 



5.5 



2.5-14.4 



3 



4-3 



5.4 



2.5-14.4 



3 



4-4 



5.6 



2.5-14.4 



3 



4-5 



5.1 



2.5-14.4 



4 



6-1 



6.3 



2.4-12.0 



5 



6-2 



5.6 



2.4-12.0 



5 



6-3 



6.0 



2.4-12.0 



5 



6-4 



6.7 



2.4-12.0 



5 



1.5-7.8 

 1.5-7.8 

 1.5-7.8 

 2.0-8.3 

 2.0-8.8 

 2.0-8.8 

 2.0-8.8 

 2.0-8.8 



38 



