 A large tropical wave , which eventually became Erika , moved off the coast of Africa on August 31 . Shortly after leaving the coast , it displayed a large low @-@ level circulation , though as it tracked westward , the circulation failed to contract significantly . It slowly organized , and by September 3 the convection within the circulation had sufficiently organized for the system to be classified as Tropical Depression Six , while located about 1150 miles ( 1850 km ) east of the southernmost Lesser Antilles . The depression moved west @-@ northwestward at approximately 20 mph ( 32 km / h ) under the influence of a well @-@ established subtropical ridge , and late on September 3 the system intensified into a tropical storm . At that time , the National Hurricane Center in Miami gave the storm the name of Erika . 
