Ifore complicated sea surface patterns also may be encountered 

 when the wind blows in violent squalls. The effect of violent 

 squalls in gales is— as every seaman or everyone who has observed 

 the sea in the more stormy parts of the oceans knows — a rather rapid 

 increase of the waves. There are more breakers to be observed and 

 the sea surface is covered with more white foam patches taking on 

 the appearance of more fierceness. But it seems that at first mainly 

 the smaller superimposed waves are increased in their size. Over- 

 taken by longer and faster running waves they pile up the crests and 

 fall forward in foaming breakers (see Chapter II, section 6). The 

 sizes of the largest waves produced by squally wind may correspond 

 to a wind velocity somewhat higher than the mean wind velocity or 

 about the average velocity of the wind within the squalls. 



Furthermore, we have to take into account that the time average 

 of the wind velocity for the most part is not constant over the whole 

 fetch. This leads to further complications and makes the practical 

 wave forecast much more difficult, especially if there is an increase 

 of wind velocity to the windward of the retch. Consider, for example, 

 a locality of observation on the western part of a low in the North 

 Atlantic Ocean within the region of NW or NNW winds. It occurs that 

 this region westward of the cold front has a large extension and 

 the wind direction is approximately the same in this sector, but 

 the wind velocity may be 2 Bft. degrees or more higher in the north- 

 ern part than at a given point of observation in the southern part. 

 From this northern region "dead sea" arrives at the point of obser- 

 vation, perhaps not even as high as in its region of origin, but 

 high enough to disturb the interference patterns of local sea at 

 the southern end of this fetch. It may happen that these more 



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