88 FREQUENCY OF WAVE CONDITIONS 



swells generated in this way are sometimes reported southward as far 

 as the northern coasts of the Galapagos Islands. 



It also seems likely that the 20-foot seas, or higher, that are reported 

 for the equatorial belt southeastward from the Hawaiian Islands, with 

 4 percent frequency for the year as a whole (p. 21, table 8), actually 

 develop there most often either in September or in February, these 

 being the only months when gales of even moderate intensity (force 7 

 or stronger) are reported there, other than on the rarest of occasions. 

 The reported frequencies, however, of high seas in low and mid- 

 latitudes in the eastern half of the North Pacific in midocean give no 

 hint of the severe cyclonic storms that occasionally blow there in 

 winter; the Pilot Chart shows the tracks of three such that developed 

 to the north of the Hawaiian Islands in the month of February, during 

 the period from 1922 to 1936. 



A corollary of the increasing frequency with which high seas are 

 reported in the northern Pacific, through the autumn, is that the only 

 regions where a low sea is reported as often as 40 percent of the time 

 by February are an isolated pool in the latitude of the northern Philip- 

 pines, of Formosa, and of southern Japan in the west, and the general 

 offing of the American coast, southward from middle California, in 

 the east. This last is also the only extensive area in the North Pacific 

 where a perfectly smooth sea has been reported in winter during 

 so much as one-twentieth of the time, though the few reports received 

 suggest that this may likewise apply along the equatorial belt in the 

 western side of the Pacific, where calm weather is equally common. 



Reports from the Sea of Okhotsk for January or February were 

 not numerous enough to be considered representative. The northern 

 and eastern parts of the Japan Sea are, however, much rougher in 

 winter (high sea 14 to 20 percent) than in summer, as is also the 

 northern part of the South China Sea (high 9 to 15 percent). The 

 sea is, however, as constantly smooth at the entrance to the Gulf of 

 Tonkin in winter as it is in summer, which applies equally along the 

 Bornean coast to the southward, as well as to the waters between the 

 southern Philippines and Celebes. 



The question, "How does the North Pacific compare for roughness 

 in winter with the North Atlantic?" is one often asked. During 

 severe winter gales the sea may be expected to rise about as high in the 

 one ocean as in the other; seas, however, more than 20 feet high have 

 been reported considerably more often along the northern routes in 

 the North Atlantic for the year as a whole (13 percent) than for the 

 North Pacific (9 percent) , the gales of winter being chiefly responsible 

 in each case. On the other hand, the area where high winter seas have 

 been consistently reported during more than one-fifth of the time 

 extends something like 300 miles further southward in the Pacific in 



