(RNN) – Tropical Storm Isaac formed late Saturday afternoon in the Atlantic between Tropical Storm Florence and Tropical Storm Helene.
The National Hurricane Center said the storm is about 1,580 miles east of the Windward Islands, which are in the West Indies.
The storm is heading west at 8 mph and packing maximum-sustained winds of 50 mph.
It's expected to speed up in the next few days as it continues moving westward. It's also expected to strengthen, possibly becoming a hurricane by Monday.
Isaac is the ninth named storm of the Atlantic hurricane season.
Tropical Storm Florence, the sixth named storm, is expected to become a hurricane Saturday night, the NHC said.
The storm could intensify rapidly by Sunday, becoming a "major hurricane" by Monday.
The storm is moving westward at 6 mph. It's about 790 miles southeast of Bermuda, with maximum-sustained winds of 70 mph.
Swells from the storm, which are likely to cause life-threatening conditions, are already beginning to affect the East Coast.
Tropical Storm Helene, the eighth named storm of the season, is 155 miles southeast of Cabo Verde, an archipelago nation off the African coast.
It's moving westward at 13 mph, with maximum-sustained winds of 60 mph.