Erin formed in the eastern Atlantic Ocean on Monday and is strengthening as it moves westward. The NHC said there is still uncertainty about what impact it could have on states like Florida on the U.S. East Coast, as well as the Bahamas and Bermuda.

As of the latest update, issued at 4 a.m. CDT Thursday, Tropical Storm Erin was located about 990 miles east of the Leeward Islands and was on a path to the west at 17 mph. (The next update will come later this morning, and updates will become more frequent once watches and warnings go into effect for the storm.)

Tropical Storm Erin is expected to become a major hurricane this weekend, the National Hurricane Center said on Thursday, Aug. 14.