12 



packed field ice until shortly after tracks F became efTective on May 

 16. On the other hand, only a few bergs were reported along the 

 Newfoundland coast. The prevaihng westerly winds and their effect 

 on field ice are believed to be partly responsible for the lack of ice in 

 tliis vicinity. Navigation in the St. Lawrence River and Gulf of St. 

 Lawrence was delayed, the first vessels passing up the Gulf on April 

 20. The Straits of Belle Isle were open to navigation on June 15; 

 however, bergs were reported along tracks G until late August. Ice 

 Patrol was inaugurated on March 24 and discontinued on August 23. 



SUMMARY OF WEATHER CONDITIONS— ICE PATROL AREA— 1939 



An unusually liigh percentage of westerly winds prevailed tlirough- 

 out the winter and late spring of 1939. This condition aided the 

 Labrador Current in the delivery of field ice and bergs along the north- 

 eastern shoulder of the Grand Banks, increased the normal amount of 

 ice, and assisted m prolonging the season. As usual, fog conditions 

 seriously handicapped the scouting activities of the patrol during the 

 summer months. Beginning in late May the cold fronts tend to dis- 

 sipate on arrival in the Grand Banks region, and only those fronts 

 that have a particularly heavy push of polar air behind them survive 

 long enough to cross the area. This frontal dissipation results in an 

 almost continuous flow of moist tropical air and the generation of fog. 

 During the month of August the percentage of fog decreased rapidly 

 and there was less tendency for the cold fronts to dissipate. Tliis 

 change probably developed as a result of the warming of the surface 

 waters by solar insolation. It is believed that conditions tliis season 

 were less boisterous than usual, and the percentage of liigh winds was 

 below normal. 



COMMUNICATIONS 



There is no doubt that the most important feature of Ice Patrol 

 is its radio communication system and efforts are constantly being 

 made to improve it. 



To facihtate copying of the ice broadcasts by vessels using the 

 various routes, information pertaining to ice or other menaces to navi- 

 gation south of latitude 45° N. was transmitted first, followed by 

 information for vessels using lanes north of that parallel. As a rule 

 there is much less ice south of latitude 45° N. and in dividing the 

 broadcast much time is saved for operators on vessels using southern 

 routes. 



As in the past, broadcasts were transmitted twice, first at the rate 

 of 15 words per minute, and retransmitted at the rate of 25 words per 

 minute. It is believed that rebroadcasting in tliis manner permits 

 the slower operators to correct errors or fill in groups missed on the 

 first broadcast. If the first broadcast was made at the faster rate, 

 less-experienced operators probably would not be able to copy any of 



