Forecasters say Tropical Storm Erin, which formed in the eastern Atlantic Ocean on Monday, is expected to become the Atlantic's first hurricane of the season. The storm formed just west of the Cabo Verde islands, off the western coast of Africa, and was moving west, the U.S. National Hurricane Center in Miami said.

The Atlantic hurricane season generally spans from June to November. According to NOAA, the likelihood of above-normal activity is 50% in the current season.

The hatched areas on the National Hurricane Center's tropical outlook map indicate "areas where a tropical cyclone — which could be a tropical depression, tropical storm or hurricane — could develop," said National Hurricane Center Deputy Director Jamie Rhome.