17 April a flight covered the St. Lawrence ice outside Cabot Strait 

 and followed the ice limits bounding the navigable steamer track 

 into the gulf as far as a line from Brion Island to Heath Point on 

 Anticosti Island. 



Third Cruise, "Modoc," 17 April to I May, 1946 



The Modoc departed Argentia, Newfoundland, at 1230 G. c. t. on 

 16 April 1946 for ice patrol. The Tampa was met and relieved as 

 surface patrol vessel at 44°15' N., 50°05' W., at 1805 G. c. t. on 17 

 April 1946. 



No cyclonic disturbances with a definite frontal system passed 

 through the ship's position during the period of this cruise. Weak 

 pressure drops and rises indicated that several low-pressure troughs 

 passed not far away. The first 4 days of the cruise the wind was 

 variable, shifting from southerly to northeast and back. Force 8 

 winds were encountered enroute to patrol after which the wind 

 averaged force 4. From the 21st through the 26th the wind was 

 steadily from the southeast gradually building up until the maxi- 

 mum of force 9 was reached on the 25th. The absence of any 

 wind shift indicated the frontal system of the low pressure area 

 was not near the Modoc. The wind force subsided and the direc- 

 tion became southerly during the last few days of the cruise. On 

 the 30th the wind swung to the northeast with force 3. The sky 

 was cloudy to overcast during the first 3 days, and from the 20th 

 until the 26th dense fog of varying depths was encountered. Dur- 

 ing the daylight hours of the 23d, with the wind increasing to 

 force 8, the fog cleared. During the last 3 days it was partly 

 cloudy to cloudy. Precipitation occurred for short periods on 

 the 17th, 25th, and 30th. During the first half of the period air 

 temperatures averaged from 38° to 44 °F. and during th6 second 

 half from 60° to 69 °F. with sea temperatures from 4° to 7° lower. 

 Pressures rose from the beginning of the cruise until it reached 

 1,032 millibars on the 18th after which five pressure drops occurred 

 reaching minima on 20, 21, 23, 25, and 29 April. The lowest 

 barometer was 1,018 millibars which occurred on the 25th. Other- 

 wise pressures ranged between 1,020 and 1,035 millibars. 



At 1100 G. c. t. on 1 May 1946, the Tampa relieved the Modoc 

 which then set course for Argentia, Newfoundland, arriving there 

 on 2 May 1946. 



A summary of the water temperature, ice, and obstruction re- 

 ports received during this cruise follows : 



Number of ice reports received 36 



Number of vessels furnishing ice reports — - 28 



Number of water-temperature reports received — - 827 



Number of vessels furnishing water-temperature reports ..— 19*0 



Number of obstruction reports received — 3 



Number of vessels furnished special information - - - 45 



135 



