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.

Tropical Storm Erin is tracking quickly westward through the open Atlantic waters and should become increasingly organized in the coming days, potentially reaching major hurricane intensity this weekend as it tracks just north of the Caribbean islands, where it could bring rain and gusty winds.