Numerical value 



D" = D) 



Thus, the corrected vj"ave height is 5-3 feet, but period and 

 travel tirae remain unchanged . 



Remarks on Forecasts 



Estimates of the probable decrease and increase of the swell 

 have to be based in part upon a prognosis of weather conditions. 

 Usually the forecaster need not construct a prognostic map but can 



50 



