 A large tropical wave with minimal convection moved off the coast of Africa near Dakar between August 14 and August 15 . It moved westward , and gradually developed thunderstorms across the wave axis . On August 21 , while located about 450 miles ( 725 km ) east of the Lesser Antilles , convection increased further within the system , though unfavorable upper @-@ level wind shear prevented rapid development . It continued to become better organized , and though a Reconnaissance flight into the system reported strong winds , it lacked a surface circulation . Late on August 21 the wave passed through the northern Lesser Antilles , and subsequent to a decrease in wind shear the system became much better organized on August 22 . A surface circulation formed , and the system developed into Tropical Storm Dean on August 22 near Saint Croix . Dean was upgraded directly to a tropical storm due to the presence of 50 mph ( 80 km / h ) winds in the storm . 
