isothermal bubble occupies an area approximately 65 kilometers lon^ bet- 

 ween the slope and the northern ed^e of the Gulf Stream. Maximum thick- 

 ness of the bubble was approximately 155 meters. Also of interest is the 

 increase in layer depth from less than 32 meters inshore of the northern 

 edge of the Gulf Stream to about 65 meters within the Gulf Stream. 



Table 1 



Variability of Near-Surface Thermal Structure 



(percent) 



Subsurface 

 Temp . Max . 



No. 

 Obs, 



warm ( i ai'C) 40 



boundary (19° to Zl^C) 41 



cool (< 19°C) 38 



Zero Layer Depth 

 Shallow * Deep* Shallow Deep Other* * 







5 



10 



70 



5 



5 



20 



37 



32 







26 



7 



56 







27 



*Shallow: water depth less than 150m 

 Deep: water depth greater than 500m 

 **Includes all other thermal structures, regardless of depth 



A profile on 12 and 13 October along 36°56'N between 73°W and 75''W 

 (figure 15) delineates the cold wedge adjacent to the slope and the 

 associated temperature inversion to the east. The structure of these 

 features is less complex than that of the sections taken in the warm 

 water to the south. The widths of the cold wedge and the interval between 

 the wedge and the cold parcel to the east are about 24 and 20 kilometers, 

 respectively. The inversion was tracked for approximately 92 kilometers 

 without reaching the eastern boundary. Near-surface water less than 10° C 

 was observed only in the wedge. Layer depth in deepwater (mean 28 meters) 

 was slightly deeper than over the shelf (mean 23 meters). 



Weather observations recorded every 6 hours at Chesapeake Light Station 

 are shown in figure 16 for 1800Z 17 September to 2400Z 13 October. Portions 

 of the record corresponding to Phases I and II are indicated along the 

 time scale. Phase I was characterized by variation in the air temperature 

 from a low of 19.5°C to a high of 23.0°C, little or no wind, and moderate 

 cloud cover. Phase II was characterized by variation in air temperature 

 from a low of 17.5°C to a high of 21.5°C, relatively high winds, and pre- 

 dominantly overcast skies. Frontal passages are indicated by increase in 

 both wind speed and cloud cover. Evacuation of the light station from 

 earlv 16 September to late 17 September precluded weather observations 

 during Hurricane Uoria. 



Heat budget computations were made by the James (1966) method for the 

 5 days that SANDS remained in the area of the warm water. Table 2 gives 

 the computed values for each of the factors involved in heat exchange 

 across the air-sea interface in the warm water and in the surrounding 

 cold water. Each water tvpe was assigned a representative SST for compar- 



