continues high. Pressures are slightly higher in the Icelandic 

 low pressure cells and fewer intense cyclones develop or move 

 along the Atlantic Arctic Front. With the eastward shift of the 

 Arctic Anticyclone, the winds become more variable along the 

 northern Alaskan coast. 



During the summer months, the pressure gradients are weakest 

 over the entire arctic region, and the winds are quite variable. A 

 separate anticyclonic center occurs to the east of Greenland, while 

 the principal Arctic Anticyclone continues its eastward movement 

 along the eightieth parallel, to approximately the 150°-155° W. 

 meridians, but with greatly diminished intensity. Winds are pre- 

 vailingly northeasterly along the Alaskan and Siberian coasts, and 

 north to northwest over the Canadian archipelago. While few in 

 number, cyclonic storms may penetrate any section of the arctic 

 at this season. The weather in the Canadian archipelago is domi- 

 nated by semi-permanent cyclonic activity with centers located in 

 Baffin Bay and northwest of Ellesmere Island. 



The low pressure center which is semi-permanent over Baffin 

 Bay is a natural result of the blocking effect of the Greenland 

 plateau on the migratory storm centers moving in from the west 

 and southwest. Most of these migratory centers originate as 

 waves on the North American Polar Front. Some, however, result 

 from the regeneration of old Pacific Ocean occluded systems, while 

 a few are developed from various low pressure centers connected 

 with the Aleutian Low. 



The most common track of low pressure centers approaching 

 Baffin Bay in summer is produced by migratory centers originating 

 in southern Canada, east of the Rocky Mountains. These centers 

 move eastward and occlude in the area immediately to the west of 

 Hudson Bay, then gradually curve northeastward across Hudson 

 Bay and extreme northern Quebec, and finally move across Baffin 

 Island and over Baffin Bay. The area of major deepening of low 

 pressure centers on the above course is in the vicinity of and just 

 to the west of Hudson Bay. Hence, the slowest forward move- 

 ment of the centers is in this area. 



The speed of advance after leaving the Hudson Bay region is 

 approximately 25 knots, gradually slowing to 5 to 15 knots over 

 Baffin Bay, where the blocking effect of the high altitudes of the 

 plateau of Greenland is felt. The migratory lows which develop 

 as regenerations of old Pacific occluded systems originate in west- 

 ern Alberta Province, along the eastern side of the Canadian Rock- 



93 



