Weather Conditions on the Pacific Coast 

 infrabar disappears. The most marked hyperbar 

 is the one over the Pacific extending from latitude 

 25* N to 40° N and from longitude 125° to 160" W. 

 There is also a marked continental hyperbar. It 

 has been found (McAdie, 1914) that typical wet 

 winters on the coast of California occur when the 

 Aleutian infrabar is displaced eastward, overlying 

 in part the continent west of a line drawn from 

 Alberta to central California. And, as further il- 

 lustrating the control of weather, it is found that 

 dry winters occur with a displacement north and 

 west of the normal center of the Aleutian infrabar 

 and a westward extension of the continental hjper- 

 bar. In summer the Aleutian infrabar practically 

 disappears and the oceanic hyperbar moves north 

 with the result that the winds are northwest and 

 the days and nights rainless, although fogs (day) 

 are prevalent. 



Compared with other sections of the United 

 States the Pacific Coast south of Cape Mendocino 

 has few storms. The zone of maximum storm fre- 

 quency lies north of latitude 45°, and California, 

 therefore, is practically out of the storm belt. In 

 the extreme south there is, however, a storm track, 

 that of storms of the Sonora type, and during July, 

 August, September and occasionally other months 

 storms are not infrequent. Such storms seldom 

 aff'ect the weather north of the Sierra Madre. In 

 the central and northern portions of the State, there 

 are few storms in June, July, and August. In a 

 period of 64 years only 13 disturbances have been 

 recorded. In September the frequency increases 

 and in the 64-year period 14 storms have been 

 noted. The most noteworthy of these early storms 

 was that of September 22-26, 1904, which stands 

 unparalleled in the history of summer and early 

 fall rains. At San Francisco, for example, the rain- 

 fall amounted to 129 millimeters (five inches). In 

 October the number of storms reported amounts 

 to 40; November, 60; December, January and Feb- 

 ruary, about 200 each; March much less, and April 

 and May about as in November. Occasionally there 

 will be a winter month without a single storm, as 

 in December, 1876, and February, 1864.* 



• In a recent publication of the Weather Bureau (Bowie 

 and Weightman, Storms of the United States), there is given 

 in table 1 the number of lows for various sections for a 



geriod of twenty years. Storms of the North Pacific type 

 ave occurred as follows: January, 53; February, 48; March, 

 44; April, 33; May, 27; June, 16; July, 14; August, 12; Sep- 

 tember, 23; October, 28; November, 48; December, 53. This 

 table, however, is misleading for California, as many of 

 these storms pass far north of the State. The storm fre- 

 quency is much less for the central and southern portion 

 of the Pacific Coast than indicated in these figures. 



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