Soon after becoming a hurricane, Felix developed a well-defined eye as Hurricane Hunters began investigating the storm. Beginning at 1200 UTC on August 11, the hurricane began undergoing rapid deepening, and by the next day, concentric eyewalls were observed, indicative of a strong storm. On August 12, the Hurricane Hunters observed flight-level winds of , suggesting peak surface winds of 140 mph (220 km/h). At that time, Felix was located north of the Lesser Antilles, moving to the north-northwest due to an approaching trough weakening the ridge. After peak winds, Felix weakened due to stronger wind shear and its eyewall replacement cycle. The eye became indistinct and opened on August 13, and it became a minimal hurricane by August 14 with a broad inner core. Late on August 14, Hurricane Felix turned more to the west-northwest, after the trough that previously brought it northward split into two pieces of energy, one moving southward and the other moving northeastward. On August 15, the hurricane passed about 75 mi (120 km) south of Bermuda, and a building ridge was anticipated to allow Felix to continue its trajectory toward North Carolina.