WIND WAVES AND SWELL 

 PRIKCIPLES Ih FORECASTING 



Prepared for the Hydrographic Office, U. S, Navy 



by 



The Scripps Institution of Oceanography 

 University of California 



INTRODUCTION 



Study of the problem of forecasting sea and swell was started 

 at the request of the Army Air Forces and is being continued under 

 the direction of the Hydrographic Office, U. S. Navy. 



Four problems of forecasting are involved: (1) forecasting 

 the length and height of the swell in the open sea, (2) forecast- 

 ing the swell reaching exposed or partially exposed anchorages, 

 (3) forecasting the height of breakers and the araount of surf on 

 any given beach, and (4) forecasting the state of the sea in any 

 given ocean area. The first problem involves two steps: (a) de- 

 termination of height and period of the waves which emerge from 

 any given wind area and which may arrive as swell on a distant 

 coast, (b) determination of the travel time and the decrease of 

 height of the waves as they proceed from the wind area. For the 

 second and third problems an additional factor is involved, namely, 

 the determination of the transformation of the waves as they enter 

 into shallow -vater and wash the beach. The fourth problem involves 

 tv/o steDs: (a) determination of the highest waves found under giv- 

 en v-/ind conditions and (b) establishment of the relation of these 



