 A tropical wave , which was accompanied by a broad surface low pressure area , emerged into the Atlantic Ocean from the west coast of Africa late on August 26 . Tracking generally westward , the system remained disorganized for the next several days . By August 29 , the system became increasingly organized as showers and thunderstorms concentrated toward the center . Based on Dvorak satellite classifications and scatterometer surface wind data , it is estimated that Tropical Depression Twelve developed at 0000 UTC on August 30 , while located about 1 @,@ 495 miles ( 2 @,@ 406 km ) east @-@ southeast of the northern Leeward Islands . Situated to the south of a subtropical ridge , the system tracked west @-@ northwestward over warm waters . As a result , the depression strengthened into Tropical Storm Leslie by 1200 UTC on August 30 . 
