38 



cated that the depression was deepening and intensifying as it traveled 

 eastward. The winds backed still further during the 18th and finally 

 later in the day, gradually abated in force as the disturbance moved 

 out into the North Atlantic and all influence had disappeared. Track 

 E, Figure 5, is an excellent example of the birth of a cyclonic vortex 

 in the atmosphere, probably materially aided by the presence of 

 warm and cold masses of water along the southern border of the Nova 

 Scotian continental shelf. This particular cyclone had its birth over 

 the northern edge of the warm and cold water where the current 

 curves up in the great oceanic bight west of the Grand Banks. Track 

 E is an example of developments that may take place in the atmos- 



FiG. 6.— The general distribution of atmospheric pressure from April 7-16, during the nine days of 

 which there was an unseasonable stagnation in the movement of "highs" and "lows" 



phere over an ocean but where due to the scantiness of data, winds 

 sometimes even of considerable intensity can not be explained by 

 reference to the generalized weather map. 



The distribution of pressure following the events described above 

 took the form of a huge high pressure area extending from Newfound- 

 land southward over the Atlantic States to Florida. This mass of air,^ 

 however, gradually shrank in extent until on the 19th it centered over 

 the Carolinas and by the 20th it had retreated completely to join the 

 more or less prevailing "high" in the direction of Bermuda. 



An expansive area of low pressure which had lain motionless since 

 April 7 (for a period of about two weeks) over the Southwestern States^ 

 began to move about the 20th and simultaneously with the removal 

 of the high pressure described in the preceding paragraph. Its track 

 F, Figure 5, from April 18 to 20, is shown crossing northward to Lak 



