Tropical Storm Erin has formed on a path toward the Caribbean and is expected to strengthen to a hurricane later in the week as it passes by Puerto Rico. Most models forecast the storm turning upward into the Atlantic Ocean, but a few see the storm continuing onward to the U.S. mainland.

Tropical Storm Erin is expected to strengthen into a hurricane later this week in the Atlantic Ocean, according to the National Hurricane Center.

Erin’s long-range track was still the subject of much speculation, with it being too soon to rule out threats to the U.S. Many forecast models suggest the storm, which could become a Category 3 hurricane by late this week, will track westward but then turn to the north and then northeast, keeping it off the U.S. East Coast.