 A tropical wave , which likely spawned Hurricane Isaac , entered the eastern Caribbean Sea on September 27 . The system slowly organized while tracking westward and later moved to the north @-@ northwest around Hurricane Keith . Eventually , the system moved northward into the Gulf of Mexico and the Straits of Florida . The system interacted with a frontal boundary while crossing Florida on October 3 and October 4 , which caused torrential rainfall . Satellite imagery indicated the development of a circulation near Orlando . Because of its structure , the system became a subtropical depression at 1200 UTC on October 4 . About six hours later , the subtropical depression emerged into the Atlantic and low @-@ level circulation gradually moved toward the deep convection while tracking eastward . By 1200 UTC on October 5 , the subtropical depression was reclassified as Tropical Storm Leslie . While fully tropical , Leslie strengthened slightly and peaked with winds of 45 mph ( 75 km / h ) . However , it soon began interacting with a cold front and transitioned into an extratropical cyclone on October 7 , while located northwest of Bermuda . 
