to obtain a smooth profile. The observed windspeed varies in a systematic way 

 from about 65 percent of the computed windspeed at the outer edge to almost 90 

 percent of the predicted value near the zone of maximum windspeed. Reasonably 

 good agreement between the theoretical and observed windspeeds has 

 been obtained in only a few storms . This lack of agreement between the 

 theoretical and observed winds is due in part to the elementary nature of the 

 model, but perhaps equally to the lack of accurate wind records near the 

 center of hurricanes. 



Parameters obtained from fitting this model to a large number of storms 

 were given by Myers (1954). Parameters for these other storms (and for 

 additional storms) are given by Harris (1958). Equation (3-57) will require 

 some form of correction for a moving storm. 



This model is purely empirical, but it has been used extensively and 

 provides reasonable agreement with observations in many storms. Other equally 

 valid models could be derived; however, alternative models should not be 

 adopted without extensive testing. 



In the northern hemisphere, windspeeds to the right of the storm track are 

 always higher than those on the left, and a correction is needed when any 

 stationary storm model is being used for a moving storm. The effect of storm 

 motion on the wind field decreases with distance from the zone of highest 

 windspeeds. Thus the vectorial addition of storm motion to the wind field of 

 the stationary storm is not satisfactory. Jelesnianski (1966) suggests the 

 following simple form for this correction, 



Rr 



U (r) = V (3-58) 



SM 2 2 F 



R + r 



where Vp is the velocity of the storm center and %M(r) is the convective 

 term which is to be added vectorially to the wind velocity at each value of 

 r . Wilson (1955, 1961) and Bretschneider (1959, 1972) have suggested other 

 correction terms. 



3. Prediction Techniq ue. 



The best method for calculating wave conditions in a hurricane is to use a 

 numerical model such as discussed in Chapter 3, Section VIII, 6; however, for a 

 slowly moving hurricane, the following formulas can be used to obtain an 

 estimate of the deepwater significant wave height and period at the point of 

 maximum wind : 



H = 5.03 e 



Rap 

 4700 



0.29 a V, 



1 + 



w 



Metric units 



(3-59a) 



H = 16.5 e 



RAp 

 100 



0.208 a V. 



1 + 



V^ 



R 



English units 



(3-59b) 



3-83 



