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.

Tropical Storm Erin is expected to begin strengthening and is likely to become a hurricane in the next 48 hours. See storm tracker.

Tropical Storm Erin continues to move quickly west, and is expected to become the first hurricane of the Atlantic season.