Tropical Storm Ernesto heads to USVI, Puerto Rico

Tropical Storm Ernesto was gaining strength as it swirled in the Atlantic Ocean Tuesday, just days after Debby finished its trek along the U.S. East Coast. Ernesto is expected to hit near or over the Virgin Islands and Puerto Rico on Tuesday evening, the National Hurricane Center says.

As of 2 p.m. ET, forecasters said Ernesto had maximum sustained winds of 60 mph and was moving at 18 mph. It was expected o be near or over the U.S. and British Virgin Islands by Tuesday evening and pass to the northeast and north of Puerto Rico Tuesday and Wednesday.

A hurricane watch is in effect for the U.S. and British Virgin Islands, and the islands Vieques and Culebra. A tropical storm warning is in effect for St. Kitts, Nevis, Montserrat and Anguilla, as well as Guadeloupe, St. Martin and St. Barthelemy, Sint Maarten, the U.S. and British Virgin Islands, Puerto Rico, Vieques and Culebra.

Forecasters expect the storm will strengthen and become a hurricane by early Wednesday.

CBS News senior weather producer David Parkinson said "rain will be a far bigger player than wind" when it comes to Ernesto.

The storm is expected to produce between 4 and 6 inches of rain over the Leeward and Virgin Islands, and 3 to 6 inches, and maximum amounts of 10 inches, over Puerto Rico. Storm surge levels could rise as much as 3 feet and bring "large and destructive waves." The Leeward Islands could also see "considerable flash flooding and mudslides," the National Hurricane Center said.

"Some models have been suggesting a foot is possible given the topography, so can't rule out higher totals," Parkinson said. "... The U.S. remains outside of the risk zone for direct impacts, but rip currents and larger waves will be a concern along the eastern seaboard."

Ernesto marks the fifth named storm so far of the Atlantic hurricane season, which has already proven to be historic after Beryl reached record strength at the beginning of the season in above-averge temperatures of the Gulf of Mexico. NOAA has predicted an above-normal season, with 17-25 named storms, eight to 13 hurricanes, and four to seven major hurricanes.

The fifth-named storm typically does not occur until Aug. 22 , according to NOAA.