l65 

 ABSTRACT 



Hurricane HILDA crossed the Gulf of Mexico in the period September 30, 

 to October k, 196k, developing to a very severe hurricane in the central 

 Gulf. Sea temperature data available prior to the storm indicated what is 

 probably a typical late summer situation with some surface temperatures 

 running above 30 C. Beginning on October 5j a T-^ay cruise was conducted 

 over the area where hurricane winds had been observed. Using the Bureau of 

 Commercial Fisheries vessel GUS III, four crossing of the hurricane path were 

 made, one where the maximum I50 mph winds were observed, one south of that 

 where the winds had first reached 120, one north where they had decreased to 

 120, and one in shallow water (Uo fathoms), where prior data had been collected 

 by the U. S. Fish and Wildlife Service from their Galveston Biological 

 Laboratory. Bathythermograms were taken regularly to depths of 270 meters and 

 hydrographic casts to 125 meters. All four sections of observations indicated 

 similar patterns of upwelling. During the passage of the hurricane it appears 

 that sea surface temperatures over an area of some 70 by 220 miles decreased 

 by more than 5 C, and that a cyclonic ocean current system was established 

 around this area. The data collected on the GUS cruise appear to be the first 

 systematic oceanographic observations available in such a situation. Although 

 they do not permit a full description of the changes which occurred, they are 

 suitable to serve as a basis for a model from which, for example, total amounts 

 of heat lost to the atmosphere might roughly be estimated. 



INTRODUCTION 



Most of the other papers presented at this Conference have dealt with 

 the influences of the underlying sea upon the atmosphere. This one illustrates 

 an exchange in the opposite direction, a situation where intense atmos- 

 pheric phenomena brought about significant and observable changes in the under- 

 lying sea. Although changes of similar type probably are caused by certain 

 less extreme weather conditions, it is seldom that features as distinct as 

 those created by hurricane HILDA may be observed. 



Figure 1 shows the path of HILDA across the Gulf of Mexico. It may be 

 noted that the most intense stage of the hurricane occurred when it was 

 centered 25O miles offshore in waters of over 1000 fms depth. Thus, the 

 effects of the hurricane upon the sea would quite likely be similar to those 

 resulting from similar storms in the larger ocean basins . Entering the Gulf 

 of Mexico with winds less than 80 mph, the hurricane intensified to the 150- 

 mile stage and the winds again decreased to less than 120 mph during the 

 passage across the Gulf. The width of the zone having winds of hurricane 

 velocity is indicated in Figure 1. The average propagation speed of the 

 storm may be obtained from recorded dates and times. 



