Pierson 



For December 1955 and December 1959 these results were verified by the 

 data provided by the British weather ships that are equipped with the Tucker 

 shipborne wave recorder. For November 1961 verification is against the wave 

 records obtained at Argus Island by the U.S. Naval Oceanographic Office. 



Figure 1 shows the significant wave height predicted at four points sur- 

 rounding the British weather ship in December 1959 and the significant wave 

 height obtained from the records obtained by the British weather ship. Four 

 major cyclonic storms passed the weather ship during this period. The waves 

 reached significant heights of 40 feet and decreased after each storm to signifi- 

 cant heights near 15 feet. The predictions are quite good and although not shown 

 the frequency spectra check quite well most of the time. 



Our other results are equally encouraging. The November forecasts were 

 verified in a completely different oceanic area by means of records obtained by 

 a different wave recording system. The data for the November forecasts were 

 not used in developing the procedure, and, although again not shown here, the re- 

 sults are quite good. 



The 180 numbers that describe the directional spectrum show a wide varia- 

 tion of odd forms such as one would expect from sea plus swell, crossed seas, 

 and swell. Most spectra cover a range of directions in excess of 180 degrees. 

 Directional spectra cannot be verified as no data were taken to estimate them. 

 However, the directional spectra cannot be too far off because it would be virtu- 

 ally impossible to obtain the good results that have been obtained for the signifi- 

 cant height and the frequency spectra if the directional spectra were wrong. 



If a fully developed sea should occur at a particular point, the numbers pre- 

 dicted would be obtained by substituting Eqs. (5) and (6) into (7). 



Presently we are developing ways to process 300,000 ship reports so as to 

 produce wind fields for fifteen months of weather data. Forecasts of the direc- 

 tional spectra for these fifteen months will then be prepared. These results will 

 be verified against frequency spectra already tabulated by Moskowitz, Pierson 

 and Mehr. At that time, some statements can be made concerning the overall 

 accuracy of our procedures. 



REFERENCES 



Cartwright, D. E. (1963): The use of directional spectra in studying the output 

 of a wave recorder on a moving ship. Ocean Wave Spectra , Prentice- Hall, 

 Inc. 



Cartwright, D. E., and N. D. Smith (1964): Buoy techniques for obtaining direc- 

 tional wave spectra. Trans. 1964 Buoy Technology Symposium, Marine 

 Technology Soc, Washington, D.C. 



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