Results 



Since the project began in I96I a total of 27 reports, papers, and 

 manuscripts have been written as a resxilt of the hindcast project, all 

 except one by project or contract personnel. These are listed by authors 

 in chronological order at the end of this report. 



The major pxrrpose of the project - to produce by machine methods a 

 wave spectriun climatology over the Worth Atlantic Ocean - has in general 

 been realized. A series of magnetic tapes containing four times daily 

 wind directions and speeds and wave spectra hindcasts for each of 519 

 gridpoints over the North Atlantic Ocean for 15 months, including the 

 entire year 1959^ has been made available. A new spectral form for 

 fully- developed seas at wind speeds from 20 to kO knots has been 

 developed. This spectral form appears to be an improvement over pre- 

 viously proposed spectral forms. New machine programs have been devel- 

 oped for the production of wind fields from pressi^re gridpoint data and 

 ships weather reports. A better understanding of wind speed profiles 

 and drag coefficients has been indicated from the studies made. A new, 

 improved machine program for producing hindcasts or forecasts of wave 

 spectra at gridpoints over the Worth Atlantic Ocean has been made avail- 

 able. A study of the representativeness of the weather over the Worth 

 Atlantic for the year 1959 compared with seven other years from 1957 to 

 196^ indicates that the 1959 weather was generally normal except for the 

 month of December which was above normal but not anomalous. 



Conclusions and Recommendations 



1, The most serious problem in the present production of accurate 

 machine hindcasts or forecasts of wave spectra appears to be the inability 

 to produce adequate wind fields. Over la^rge expanses of the oceans there 

 is a complete lack of weather observations and even in the shipping lanes, 

 the ships may often be poorly spaced. Discontinuities of the winds, such 

 as along fronts, present a special problem since computer analysis 

 techniques tend to smooth out the discontinuities. 



2. The procedures for the observation of winds and waves should be im- 

 proved and standardized. The winds shoiold be automatically recorded at 

 perhaps several different elevations on weather ships. Anemometers 

 should be located so that the effect of the ship on the wind is elimin- 

 ated. For various tj/pes of ships a standard level above the sea surface 

 should be used for the height of the anemometer, such as' 10 m or 19.5 m 

 depending on the ship size and superstructure. Shipborne wave recorders 

 should be installed at least on the U. S. weather ships and possibly on 

 some of the Wavy ships so that more adequate wave data can be obtained 



in the Western Worth Atlantic. The winds should be recorded and averaged 

 for the same length of time as used for the wave observations, say 15 or 

 20 minutes. A measurement of gustiness, if any, should also be included 

 in the observation. The length of the wave records shoiild depend on the 

 wind speed. For example, when the wind speed is over 35 knots at an 

 elevation of 19 '5 ^} it would be advisable to take continuous recordings 

 of the waves. 



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