The key to the severity of impacts in the Leeward Islands and Puerto Rico from strengthening Erin depends on how soon a turn to the northwest occurs with a near-miss versus a direct hit.

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.