It has been suggested that many of the " extra tropical " cyclones 

 following a southerly path from near the head of the Gulf of California 

 eastward toward the lower Mississippi Valley are actually hurricane 

 residuals, reduced in intensity by long travel over land. 



Desirable Research 



Present knowledge permits a qualitative description of the hurricanes 

 of the area just west of the Mexican mainland, but does not furnish the 

 specific quantitative information necessary for accurate tracking or 

 forecasting of these Pacific hurricanes. The need for additional data is 

 known to the weather services of both the United States and Mexico, 

 and extensions of the services are now under way in both countries. 

 International co-operation, which has been excellent for several decades, 

 is now so good that both services function as a single unit during times 

 of emergency. 



Detailed study of the played-out remnants of these hurricanes, to 

 determine their effects many miles from the supposed " point of 

 extinction," appears desirable. Present knowledge, which leaves much 

 to be desired, suggests, but does not prove conclusively, that many of 

 the unpredicted squalls which cause so much damage in the western 

 United States are either hurricane residuals or are caused by these 

 residuals acting either as a " trigger," or " last straw," on pre-existing 

 instability, usually in Tropical Maritime air which has invaded the 

 region between the Rocky Mountains and the California Sierras. 



Because of the sparsity of population in man}' parts of the region 

 concerned use of automatic, unattended weather stations, reporting by 

 wire or radio, appears economically desirable, as does the use of " radar 

 tracking." 



x\cknowledgments 



During the progress of this study valuable assistance in the field was 

 received from local residents in all social and economic categories ; the 

 extremes being represented by Juan Tomas, aged and decrepit chief of 

 the allegedly cannibal Seri tribe on Tiburon Island, and Sr. Alberto 

 Celaya, Comisario of the prosperous Sonoita Oasis, in Sonora, Mexico. 

 Discussions of the problems of desert weather and cKmate with the staff 

 of the Desert Botanical Laboratory, in Tucson, Arizona, were found 

 most helpful. During the preparation of this report a large amount of 

 information was supplied the writer by the Servicio Meteorologico Mexi- 

 cano and the United States Weather Bureau. This assistance, some of 

 which required considerable special work, is here gratefully acknowledged. 



Cartographic Referenxes 



Geographic nomenclature in this paper follows, wherever possible, 

 that in Bartholomew, John, The Oxford Advanced Atlas. Oxford 

 University Press, 1942. 



Details of coastal waters, and descriptions of the various islands, are 

 contained in H.O. 84, Sailing Directions for the West Coasts of Mexico 

 and Central America, Washington (D.C.), 1937, eighth edition. 



Land features adjacent to the hurricane area are mapped on a scale 

 of 1/1,000,000 in the U.S. Coast and Geodetic Survey's Western 

 Hemisphere Pilotage Charts (available from U.S. Coast and Geodetic 

 Survey, Washington, D.C.) Code APC 3; IIM, Death Valley; 12M, 



29 



