Over the weekend, Erin is expected to rapidly intensify all the way to a Category 3 hurricane. By Monday, as the storm steers away from the Caribbean and toward Bermuda, it's now forecast to hit Category 4 with 130 mph sustained winds. Some long-term computer models suggest it could get even stronger and hit Category 5 in the open ocean.

Tropical Storm Erin is on the cusp of strengthening into a hurricane, which it is expected to become later this Friday, as it bears down on the northern Caribbean islands.

Heavy rains were forecast to start late Friday in Antigua and Barbuda, the U.S. and British Virgin Islands, and southern and eastern Puerto Rico. Up to 4 inches (10 centimeters) are expected, with isolated totals of up to 6 inches (15 centimeters), according to the National Hurricane Center in Miami. Forecasters also warned of dangerous swells.