23 



A storm may also originate when the Polar Front trails 

 southwestward and approaches the high pressure belt. If 

 this occurs, warm maritime tropical air may be brought in 

 contact with cold polar maritime air resulting in cyclogenesis, 

 usually located about one third the distance between the 

 Hawaiian and Aleutian Islands. If the contrast of the air 

 masses is severe enough, cyclones may be formed which move 

 eastwardly and eastnortheastwardly toward North America. 



These secondary cyclones usually have strong westerly 

 winds behind their cold fronts and heavy to moderate swell 

 is sent on its way toward the southern California coast and 

 may succeed in reaching the area by way of the Santa Barbara 

 Channel. Swell with a 280° source and a 13 second period is 

 representative from such an origin, and the direction and 

 period is believed to be applicable also to those North 

 Pacific storms which assume a southern track. 



Storm tracks are farther south in the winter than in the 

 summer, so there is a greater frequency of significant swell 

 from these storms in the winter. Even in June and July, 

 however, conditions may be such that this type of generation 

 area is important. 



The secondary cyclones mentioned above frequently occur 

 in families so that as many as six similar storms may march 

 across the ocean, all following a similar path. On such 

 occasions, swell continues to arrive uninterrupted, but with 

 fluctuations depending on the vagaries of each storm. At 

 other times the secondary lows are diffuse and contain compli- 

 cated frontal systems. With these conditions the winds are 



