Tropical Storm Felix formed over the Windward Islands early Saturday, U.S. forecasters said. At 5 a.m. EDT (0900GMT), the storm was centered about 30 miles (48 kilometers) northwest of Grenada, according to the National Hurricane Center. It had top sustained winds of 40 mph (64 kph), just above the threshold to be a named storm. The government of the Netherlands Antilles and Aruba, in the Caribbean, issued a tropical storm warning for the islands of Aruba, Bonaire and Curacao. The storm was moving westward at about 18 mph (29 kph), and that general motion was expected to continue over the next 24 hours. Felix was expected to move away from the southern Windward Islands later Saturday morning and to pass near Aruba, Bonaire and Curacao by evening or early Sunday morning, forecasters said. The storm was expected to strengthen over the next 24 hours, forecasters said. The Air Force planned to investigate Felix later Saturday morning, they said. Felix is the sixth named storm of the Atlantic Hurricane Season, which runs from June 1 to Nov. 30.