Tropical Storm Erin is forecast to strengthen into the first hurricane of the Atlantic season by Saturday morning and then become a major Category 3 hurricane by Sunday morning as it passes north of Puerto Rico. But as of now, Erin is not expected to pose a direct threat to the U.S.

Tropical Storm Erin formed in the eastern Atlantic Ocean on Monday, forecasters said. The storm could strengthen to become the Atlantic's first hurricane of the season.