Aug 15 (Reuters) - Hurricane Ernesto on Thursday strengthened into a Category 2 hurricane as it barreled toward Bermuda threatening major damage over the weekend from powerful winds and heavy rain, after leaving hundreds of thousands of Puerto Ricans without power.

Ernesto is forecast to strengthen further before it reaches Bermuda late on Friday, a British island territory far out in the Atlantic, the National Hurricane Center (NHC) said.

At 11 p.m. ET on Thursday (0300 GMT Friday) it was 410 miles (660 km) south-southwest of Bermuda as it headed north, packing winds of 100 mph (155 kph).

"Additional strengthening is forecast during the next day or so, and Ernesto could be near major hurricane strength on Friday. Ernesto is forecast to be a large hurricane near Bermuda on Saturday," the hurricane center said.

A major hurricane is a Category 3, 4 or 5 on the five-step Saffir-Simpson Hurricane Wind Scale and is capable of causing devastating or even catastrophic damage.

The storm could produce up to 15 inches (38 cm) of rain that could result in life-threatening flash flooding, the hurricane center said.

Only 11 storms have made direct landfall on Bermuda, an archipelago of 181 islands with a population of 64,000, since records began in 1851.

Hurricanes Gonzalo in 2014 and Fabian in 2003 were the most destructive storms to hit Bermuda in recent memory, causing hundreds of millions of dollars in damage and leaving most of the islands without electricity. Fabian killed 4 people, the first storm to cause deaths on the islands since 1926.

Ernesto became a hurricane on Wednesday after leaving Puerto Rico as a tropical storm, where it battered the island with heavy rainfall. Images and video from the island showed flood waters covering roadways, downed power lines and destroyed homes and vehicles.

As of Thursday afternoon, some 407,000 homes and businesses - about a quarter of all customers on the U.S. territory - remained without electricity, according to LUMA Energy, the Caribbean island's main power supplier. LUMA said it had restored power to 300,000 customers.

Vanessa Toro, a San Juan resident who lost electricity early on Wednesday morning, said she was frustrated that she was still without power even though the storm itself had little impact on her area.

"If the event had been of a large magnitude, one understands the situation a little more, but this storm was not catastrophic," she said. "Then LUMA says it is prepared to deal with these situations, but we are without power 29 hours after the storm."

LUMA Chief Executive Juan Saca said in a radio interview on Thursday morning he expected power to be restored to many customers later on Thursday.

Puerto Rico's power grid is notoriously fragile. In 2022, Hurricane Fiona knocked out power for about 80% of the island's homes and businesses for as long as a month. Five years earlier, Hurricanes Irma and Maria destroyed the island's power grid and caused outages in some areas that lasted nearly a year.

Ernesto was expected to stay well west of the U.S. East Coast as it traveled north over the ocean. However, the storm was forecast to produce life-threatening surf and rip currents across the region, the center said.

Ernesto is the fifth named Atlantic storm of what is expected to be an intense hurricane season. Slow-moving Debby hit Florida's Gulf Coast as a Category 1 hurricane just last week before soaking some parts of the Carolinas with up to 2 feet (60 cm) of rain.

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https://www.reuters.com/world/americas/ernesto-leaves-third-puerto-rico-without-power-it-heads-toward-bermuda-2024-08-15/