 On August 11 , a tropical wave moved off the west coast of Africa , and , encountering favorable conditions , quickly spawned Tropical Depression Four , roughly 520 miles ( 835 km ) west @-@ southwest of Cape Verde . The depression moved briskly westward , south of a deep layered ridge , and was upgraded to Tropical Storm Dean on August 14 . The storm continued to strengthen overnight as it gained organization , and became the first hurricane of the season on August 16 . On August 17 the eye of the hurricane passed into the Caribbean between the islands of Martinique and Saint Lucia as a Category 2 hurricane . 
