By Ivelisse Rivera and Tyler Clifford
SAN JUAN, Puerto Rico (Reuters) -Tropical Storm Ernesto threatened on Tuesday to bring heavy rainfall, dangerous storm surges and strong winds to the U.S. and British Virgin Islands and Puerto Rico, leading the U.S. territory to close schools and prepare for power outages.
Hurricane conditions were possible as the storm passes over or near the Virgin Islands, Culebra and Vieques on Tuesday evening on a route that would likely bring it just northeast of Puerto Rico, the National Hurricane Center said.
It was packing sustained winds of 65 mph (105 kphour) as of Tuesday night, when it was centered 60 miles (96 kilometers) east-northeast of San Juan and moving to the northwest at 17 mph (28 kph).
A storm is considered a hurricane when its sustained winds reach 74 mph (119 kph), which could come early Wednesday morning.
President Joe Biden late Tuesday approved an emergency declaration for Puerto Rico, which facilitates federal support for the island in any recovery.
Ernesto will strengthen further after passing over Puerto Rico and veering north into the Atlantic, the hurricane center said. Later it is expected to buffet Bermuda, but the center said it was too early to forecast the impact it would have on that British island territory.
"We anticipate a rapid intensification ... over the next 12 hours to potential Category I hurricane," said Daryl Jaschen, director of the U.S. Virgin Islands Emergency Management Agency, during a briefing. He said the territory could get up to 8 inches (20 cm) of rain.
Airports and seaports were closed on Tuesday afternoon, Jaschen said. Schools will also remain closed through Wednesday.
Ernesto is the second named Atlantic storm in a week. Slow-moving Debby hit Florida's Gulf Coast as a Category 1 hurricane last week before soaking some parts of the Carolinas with up to 2 feet (0.6 meter) of rain.
LUMA Energy, the private operator of Puerto Rico's transmission and distribution system, said on X it had activated its emergency operations, mobilized crews ahead of the storm, and advised residents to brace for power outages. The company said on its website that just after 10 p.m., nearly 11,300 clients were without power.
Joseph Niskar, a lawyer who moved to Puerto Rico from Michigan after Hurricane Maria struck the island in 2017, said he was preparing for extended periods without water or electricity.
"I bought a generator big enough to run my refrigerator and fans to keep cool, but will need gasoline that can be hard to get because a lot of people wait until the last minute and there can be long lines," Niskar said.
Like Debby, Ernesto's greatest threat is torrential rain, which could spur flash floods and landslides, especially in the mountainous interior of Puerto Rico and nearby Caribbean islands.
Total rainfall in some spots in Puerto Rico could reach up to 10 inches (25 cm), the NHC said. Storm surges could bring water levels as much as 3 feet (1 meter) above ground level on Puerto Rico's eastern coast and in the Virgin Islands.
On Monday, Puerto Rico Governor Pedro Pierluisi activated more than 200 National Guard members and expedited food benefits for families ahead of the storm's arrival. Government workers were given the day off, with the exception of essential personnel. Officials also postponed the first day of school from Tuesday to later in the week.
Puerto Rico, with its fragile power grid, has a history of highly destructive storms. In 2022, Hurricane Fiona knocked out power for about 80% of the island's 1.5 million homes and businesses for as long as a month.
Since Fiona, Congress has approved $1 billion in funds to modernize and stabilize the grid in Puerto Rico.
Five years earlier, Hurricanes Irma and Maria destroyed the island's power grid and caused outages in some areas that lasted nearly a year.