During the last four decades, as a result of careful studies by the 

 Servicio Meteorologico Mexicano, our knowledge of these west-coast 

 hurricanes has been considerably augmented. Within the last fifteen 

 years, as the smaller coastwise vessels have been equipped for radio 

 communication, and the settlements on the Sonoran coast and in 

 peninsular California have been linked to central Mexico by wire and 

 radio, the number of reports of hurricanes, locally known as cordonazos, 

 franciscos, or chubascos{^), has more than tripled, so that the Mexican 



Meteorological Service is now able to plot the trajectories of some major 

 hurricanes in the eastern Pacific with gratifying accuracy. A sample 

 chart, showing trajectories of tropical cyclones in this area during the 

 year 1936, substantially as plotted by the Servicio Meteorologico 5lexi- 

 cano, comprises Fig. 1. 



History 



Probably the earliest records of Mexican west-coast hurricanes are 

 those to be inferred from the non-arrival of the annual Manila Galleon (6) ; 

 and from the fragmentary reports of " tempestades " to be found in the 

 " Documentos Para La Historia De Mexico (7) ". One such description, 

 written in 1730, probably by Cristobal de Canas, missionary at Arispe, 

 Sonora, indicates that hurricane behaviour was known, and at least partly 

 understood, prior to that year (8). 



Later findings, ably summarized by Hurd(9), show a definite increase 

 in the number of hurricanes reported as the amount of sea travel in the 

 eastern Pacific increased, so that during the past four decades an average 

 of slightly more than six hurricanes has been reported annually. The 

 present hurricane reporting situation, although much improved over 

 even ten years ago, is still far from satisfactory, and has been ablj' 

 summarized by Hurd " the ' accidental ' encounter of a ship with a violent 

 tropical cyclone in these waters continues, for scarcely a year passes in 

 which some storm owes the only record of its existence to the passage 

 of a single vessel across its path." 



If and when the radar tracking procedures, now used in the Caribbean, 

 are expanded to cover also the Mexican coastal waters, this shortage 

 of information will be rectified. 



Frequency of Tropical Cyclones 



Temporal distribution of tropical cyclones in Mexican west-coast 

 waters is still problematical, for the aforementioned lack of data makes 

 any estimate subject to a large possible error. By adaptation of the 

 physicists' " mean free path " computations, it appears that about 

 fourteen such disturbances occur in an average year, there being a possible 

 error of plus or minus two in this figure. 



(^) These terms, the first two of which are local variants of " El Cordonazo de 

 San Francisco " (the lash of St. Francis), are applied to almost any violent mnd- 

 storm, whether it is a true hurricane or merely a violent local squall. The term 

 hurricane, variously pronounced, is also employed in the same general sense ; and 

 the term ciclon tropical (tropical cyclone) is commonly used by Mexican meteorolo- 

 gists. There are also a multitude of local terms, derived in pai't from American 

 Indian languages, by which hurricanes are designated. [Hurricane is probably 

 derived from one of the Carib dialects, its original meaning being evil spirit, or 

 bad medicine.) The term typhoon is heard occasionally in some areas near the 

 Gulf of California, it apparently having been learned from Japanese fishermen. 



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