92 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



JANUARY 



AVERAGE SEA LEVEL PRESSURE (INCHES) 

 AVERAGE AIR TEMPERATURE (" F) 

 OVERAGE WATER TEMPERATURE CF) 



WIND; Arrows flt with tke wind Length of arrow aivES percent of total observations to sixteen 



POINTS OF THE COMPASS BarBS SHOW FORCE ON BEAUFORT SCALE. FlQURE IN CENTER OF CIRCLE GIVES 



percentage of light, variable winds. 



to 20 SO 40 50 60 70 80 90 lOO 



Scale of Wind Percentages 



Figure 19. — Average sea level pressure (inches), average air temperature (°F.), and average water temperature (°F.) 



January. 



which have the greatest frequency — greater than 

 30 percent of all observations — in the summer and 

 fall in a band extending from the Yucatan Channel 

 northwestward across the Gulf. Altostratus and 

 altocumulus are common the year-round, their 

 average frequency being from 10 to 20 percent 

 throughout the Gulf. In the summer and fall 

 cumulonimbi are observed about 10 percent of 

 the time in the western and northwestern regions. 



The period of lowest occurrence of rainfall over 

 the open water is in the spring when less than 5 

 percent of the observations show rain according 

 to the Atlas of Climatic Charts of the Oceans. 

 The remainder of the year the frequency is 5 to 

 10 percent over most of the Gulf except for an 

 area around the Yucatln Peninsula where fre- 

 quencies drop below 5 percent in the winter and 

 summer. A study by Kloster reported in the 



