During the cool season the Gulf of Mexico, the south- 

 western part of the Caribbean Sea, the Gulf of Tehuan- 

 tepec on the Pacific side of southern Mexico, and 

 western coastal waters of Costa Rica, are more or 

 less subject to northerly winds which occur as a result 

 of the southward extension into the Gulf of Mexico of 

 strong anticyclones from the Plains States .... North- 

 ers usually have their greatest strength and frequency 

 during the periods from November to February, in- 

 clusive, but conditions favorable to their development 

 may occur as early in the season as October and as 

 late as April. 



The northerly gales of the cooler months which occur 

 in the GulfofTehuantepec are known as Tehuantepecers. 

 The Tehuantepecer results from the anticyclone to the 

 northward. It is frequently, in fact commonly, a wind 

 of greater force than the norther of the Gulf of Mexico 

 which feeds it ... . Its cause is a strong flowing of 

 anticyclonic air through the comparatively low and 

 narrow Tehuantepec Pass, from which it emerges upon 

 the Pacific slope. It then pours violently down to the 

 Gulf of Tehuantepec, and frequently overspreads the 

 entire Gulf. It often continues at sea far southward .... 



The wind direction may be from west-northwest to 

 east, with northwest to northeast as the most common 

 directions .... 



At Salina Cruz the north-northeast wind throughout 

 the year averages force 6, and the north wind averages 

 between forces 4 and 5. . . . 



Figure 2A represents average surface wind 

 roses for different periods of the year for an 

 ocean area centered at 14° N.,96° W., adapted 

 from monthly charts (U.S. Navy, 1955). More 

 winds are observed from the north than from 

 any other direction throughout the year, es- 

 pecially from October through April; the only 

 other winds of any consequence during this 

 period are from the northeast, northwest, 

 and west, the last becoming more frequent 

 in the spring months; the average velocity 

 of north wind is over 16 miles per hour 

 (i.e., over Beaufort force 4) from October 

 through January and over 10 miles per hour 

 (i.e., over Beaufort force 3) from February 

 through April. The period June through August 

 is characterized by light or gentle winds from 

 the north, northeast, and east. May and Sep- 

 tember are months of variable winds, light 

 or gentle on the average. Southerlies are 

 infrequent at all seasons. 



PREVIOUS OCEANOGRAPHIC 

 INFORMATION 



Mean surface temperature 



The Gulf of Tehuantepec is in the thermal- 

 equatorial region of the eastern Pacific, which 



A AVERAGE SURFACE WIND 



o 



20 



JUM-AUG 



FREQUENCY 



(>3,>4 BEaUFOHT) 



FEB-flPR 



98<> 



JUN--AUG. OCT.-JAN. FEa-APR. MAY 8 SER 



B AVERAGE SURFACE CURRENT (schematic chart) 



Figure 2.--Average surface wind and surface current in the GulfofTehuantepec: 

 current diagrams schematic; broken and unbroken arrowsindicate, respectively, currents 

 less than and more than 10 miles per day. 



