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 may near Puerto Rico and the Dominican Republic before likely turning north as a hurricane, sparing the U.S.

The National Hurricane Center said Tropical Storm Erin is expected to begin strengthening today, Aug. 13 and become a hurricane Friday, Aug. 15, and a strong Category 3 hurricane by Sunday, Aug. 17 as it moves out of an area with dry area and "marginal" sea surface temperatures.