MARINE METEOROLOGY OF THE GULF OF MEXICO, A BRIEF REVIEW 



By Dale F. Leipper, Department of Oceanography, Agricultural and Mechanical College of Texas 



The best general summary of the weather over 

 the Gulf of Mexico in nontechnical langjuage is 

 probably that prepared by the United States 

 Weather Bureau for the United States Coast Pilot 

 (1949).  There are a number of articles on the 

 general circulation of the atmosphere and on 

 meteorological processes without specific reference 

 to the Gulf of Mexico which, nevertheless, pertain 

 to this region as well as to all similar regions. It 

 will not be attempted to review such articles in 

 the present summary. Two references of this type 

 are Holmboe, Forsythe, and Gustin (1948), and 

 Byers (1944). In addition, there are some publi- 

 cations such as Riehl (1947) which deal with the 

 general weather in the low latitudes and are 

 helpful in understanding the Gulf of Mexico 

 weather more completely. 



EXTRATROPICAL CYCLONES 



Saucier (1949) has analyzed the frequency and 

 behavior of extratropical cyclones originating on 

 or near the northwestern coast of the Gulf of 

 Mexico over a 40-year period. These cyclones 

 have marked effect upon the weather of the Gulf 

 as well as upon that of much of the eastern United 

 States. They occur on the average about 10 

 times per year with a maximum number of 19 

 occurring in 1899 and a minimum of 2 in 1916. 

 The high frequency of these storms appears to 

 result from the influence on the general circulation 

 of the warm moist surface provided by the Gulf 

 of Mexico, the cold continental air to the north, 

 and the mountains to the west. It was found that 

 the cyclones seldom occurred immediately after 

 a deep cold air mass penetrated the entire Gulf 

 of Mexico but were most common when it remained 

 north of the Gulf coast. The storms may begin 

 as early as October. The maximum number 

 occurs in January. Very few occur later in the 



' Contribution from the Department of Oceanography of the Agricultural 

 and Mt'chanieal College of Texas, Oceanographic Series No. 20. Based in 

 part upon work done under the sponsorship of the Office of Naval Research 

 and the .\ir Force Cambridge Research Center. 



2 References are listed at the end of the chapter. 



spring than April. The regions of formation, 

 directions of motion, and the characteristics of the 

 intensification of the 388 cyclones studied are 

 discussed. 



THE GENERAL AIR CIRCULATION AND 

 SOME OF ITS CONSEQUENCES 



The Bermuda atmospheric high pressure cell 

 dominates the circulation over the Gulf, partic- 

 ularly during the spring and summer months. 

 In the late summer there is a general northward 

 shift of the circulation and, as shown in figure 17, 

 the Gulf comes under the more direct influence of 

 the equatorial low pl-essure belt. The constancy 

 of the Bermuda high tends to maintain steady 

 circulation and to govern the climate during the 

 summer. Summer conditions are illustrated in 

 figure 18. No isotherms appear for average water 

 temperature (sea surface temperature) since the 

 waters are nearly uniform at about 84° F. as 

 illustrated in the chapter on physical oceanog- 

 raphy.' The air temperatures on the average are 

 also quite uniform and high. The southerly posi- 

 tion of the Bermuda cell brings about the south- 

 east-northwest orientation of isobars across the 

 Gulf and leads to a predominance of southeasterly 

 winds, as shown by wind arrows. The winds 

 tend to become more soullu>rly in the northern 

 part of the Gulf. In this region there are prac- 

 tically no northerly winds in summer and only a 

 relatively few from the east or the west. In 

 the more southern parts of the area the predomi- 

 nance of the easterly and southeasterly flow is 

 even more marked. 



With a typical summer circulation in the Gulf 

 and the uniform average sea surface temperature, 

 there would be expected only a minimum lunnber 

 of local weather features over the water which 

 are the type caused within the Gulf by air flow 

 toward successively warmer or cooler water sur- 

 faces. However, on a larger scale the relatively 



I See Physical Oceanography of the Gulf of Mexico, p. 119. 



89 



