NORTH PACIFIC 87 



within which a high sea is reported during more than 20 percent of 

 the time expand, by February, to include the whole vast area south- 

 ward to the latitude of southern Japan in the west and to that of Lower 

 California in the east (to about latitude 25° N.), excepting only for 

 the smoother tongue that still intervenes between it and the United 

 States coast, in the east, as just noted. 



The southern limit of this tumultuous region does not differ much 

 in position anywhere across the Pacific from the corresponding 

 boundary of the area where severe winter gales have been reported 

 on more than 5 days out of 100 during past years. Indeed, it is only 

 where the frequency of gales of force 8 is greater than 10 percent that 

 consistent reports have been received of high seas with frequency 

 greater than 35 percent from any part of the North Pacific at any time 

 of year. 



The autumnal roughening of the ocean is also accompanied by a 

 reversal in the relative frequencies with which the sea runs high in the 

 coastal belts of the two sides of the Pacific in mid-latitudes ; in summer, 

 this happens more often along the California coast than along the 

 Japanese (pi. IX), whereas in February the reverse is true (12 to 

 31 percent high along the Japanese islands, 3 to 14 percent high from 

 southern California to Puget Sound) . 



The greater frequency of high seas in the waters between Japan, 

 Korea, the China coast, and the Philippines in February (0 to 28 

 percent) than in August (0 to 13 percent) reflects the general increase 

 that takes place there through the autumn in the average strength of 

 the wind, rather than the effects of typhoons, for these seldom develop 

 there in winter. The expansion that takes place from summer to 

 winter of the area within the Northeast Trade Wind Belt, where a 

 9-foot sea is more than an exceptional event (see the contours for 

 10 percent "high," pis. IX and XIII), has a similar cause. And gales 

 of moderate strength (force 7 or higher) blowing more commonly in 

 winter (up to 10 percent) off southern Mexico, than in summer, are 

 no doubt responsible for the fact that high seas are reported a little 

 more often off the Central American coast from Costa Rica northward 

 (up to 7 percent) in February than in summer ( 1 to 3 percent) . Well- 

 known examples are the rough seas generated in the Gulf of Tehuan- 

 tepec by the gales, known locally as "Tehuantepecers,"' that blow out 

 from the land there in late autumn and winter at times when cold 

 air masses are flowing in sufficient strength southward from the North 

 American continent, and along the western side of the Gulf of Mexico, 

 to be funneled, as it were, across the Isthmus of Tehuantepec. 28 The 



w See Hurd, 1929, Monthly Weather Review, vol. 57, No. 5, p. 192, for a readable account 

 of these "Tehuantepecers." 



