On August 22, a tropical wave moved off the coast of Africa, and it moved westward across the Atlantic Ocean and Caribbean Sea without developing significantly. On September 1 the wave axis entered the Gulf of Mexico, and upon doing so convection steadily organized around a low-level center of circulation. The system moved northward and developed into Tropical Depression Twelve on September 3 while located about 300 miles (480 kilometers) west of Tampa, Florida. Embedded within a slow mid-latitude trough, the depression moved eastward and strengthened into Tropical Storm Henri on September 5.