Marilyn came from a tropical wave that formed off the African coast to the eastern Atlantic Ocean on September 7 and September 8. Large, low-level winds were included in the wave's circulation. However, little convection existed. The system continued west for a few days at about . On September 12, what was to be Hurricane Marilyn was named Tropical Depression Fifteen after convection increased. TD-15 strengthened quickly, and became Tropical Storm Marilyn six hours later. Four hours later Tropical Storm Marilyn became Hurricane Marilyn.