southern Mexico and Guatemala in February are caused by northerly winds from the Carib- 

 bean. There are large regions in the southeastern portion of the area where there is greater 

 than 80 percent frequency of winds equal to or less than 5 m/sec. This and other areas 

 where there are a high percentage of light winds are generally out of the major influence of 

 the trade winds. In the areas where trade winds are strong, light winds usually represent 

 only 10 to 30 percent of the total. Although high velocity winds are not common to most 

 of the area, hurricane-force winds (> 33 m/sec) caused by strong tropical cyclones have 

 been reported as far north as 30°N (once in 6 years) and more frequently south of Baja 

 California in the vicinity of 20°N, 1 1 5°W (12 times in six years) and to the west towards 

 Hawaii (Figures C.5 tlirough C.8). Wind velocities in these areas in excess of 50 m/sec have 

 been reported (62 m/sec winds were measured in Hurricane Maggie, 480 kilometers south of 

 Baja California in 1974, Ref. 44). Strong local winds are frequent during the winter in the 

 Gulf of Tehuantepec and along the Central American coast (17°N to 8°N). These winds 

 reach gale strength during periods of high pressure over the Caribbean and Gulf of Mexico. 

 Local nearshore gale-force winds associated with violent thunderstorms are relatively com- 

 mon along the west coast of Mexico and Central America during the summer months. 



Figure 30 gives a summary of environmental data for the central northeast Pacific, 

 including percent frequency of wind velocity > 1 7 m/sec for two Ocean Weather Stations 

 (OWS N, 30°N, 140°W, and OWS P, 50°N, 145°W) and four quadrangles in between. The 

 value of the OWS data is that the weather observation ships were continuously manned by 

 professional observers for over twenty years (including periods of severe weather). Other 

 data sources are usually from ships of opportunity and have a fair weather bias because most 

 ships tend to avoid bad weather (Ref. 27). It is apparent from Fig. 30 that there is a marked 

 reduction in frequency of gale-force winds from OWS P south to OWS N. At OWS P gale- 

 force winds occur more than 10 percent of the time during January through March and 

 October through December. The peak months are November and December where gale- 

 force winds blow over 20 percent of the time. At OWS N, winds of greater than 17 m/sec 

 occur near 1 percent of the time in January, February, and December and occur rarely, if 

 ever, between June and September. Areas 1 through 4 show intermediate frequency struc- 

 tures. Figures 3 1 and 32 are monthly persistence graphs of gale-force winds for OWS N and 

 P. These graphs depict the cumulative percent frequency of hours of duration of the event 

 (winds > 17 m/sec) equal to or less than the number of hours intersected by the soHd curve; 

 and also depict days interval between events equal to or less than the number of days inter- 

 sected by the broken curve. 



At OWS N winds of 1 7 m/sec or greater are of short duration, and there is generally 

 a long period of time between the events. There are very few winds of high velocity during 

 May and October. At OWS P, winds of 17 m/sec or greater are not uncommon during any 

 month; the longest duration of event and shortest period between events occurs January 

 through April and September through December (Fig. 32). Persistence graphs of low- 

 velocity winds (>2.5 m/sec) will give an estimate of total wind energy available if wind 

 powered energy sources are considered for upwelhng apparatus. Figures 33 and 34 present 

 persistence graphs for winds >2.5 m/sec for OWS N and P, respectively. 



In summary, the most severe persistent winds are in the northern portion of the 

 survey area and frequently are associated with extratropical storms in the fall and winter. 



23 



