From today's WSJ:

By Talal Ansari and
Arian Campo-Flores
Updated Aug. 28, 2019 2:08 pm ET

Dorian became a hurricane as it headed toward the eastern coast of Puerto Rico on Wednesday afternoon, where residents had prepared for a lashing of heavy rains and high winds only two years after the island endured Hurricane Maria’s devastation.

As of midday Wednesday, the storm had maximum sustained winds of 75 miles an hour with even higher gusts, according to the National Hurricane Center.

Puerto Rico’s main concern is heavy rainfall, which could provoke flooding and landslides, said Roberto García, a National Weather Service meteorologist in San Juan. But for the islands of Vieques and Culebra, off Puerto Rico’s eastern coast, strong winds could prove a more-significant factor, he said.

After making landfall in Puerto Rico, Dorian is forecast to grow into a Category 3 hurricane as it heads toward the east coast of Florida.

“All indications are that by this Labor Day weekend, a powerful hurricane will be near the Florida or southeastern coast of the United States,” the NHC said.

Carlos Acevedo, commissioner of Puerto Rico’s emergency management agency, said the National Guard was prepared to move supplies to affected areas. He said he had spoken to many of the territory’s mayors, some of whom requested generators, tents and other equipment.

Mr. Acevedo said 23 shelters were open across Puerto Rico, and a smattering of residents had begun to show up. Power and water service largely were functioning normally, he said. The island’s ports had been closed, and some airlines had canceled flights.

“To the citizenry, remain calm,” Mr. Acevedo said.

Late Tuesday, President Trump approved an emergency declaration for Puerto Rico ahead of the storm, ordering federal assistance to supplement local response efforts.

Puerto Rico Gov. Wanda Vázquez declared a state of emergency on Monday. The entire island is under a hurricane watch, as well as tropical storm and flash-flood warnings, according to the National Weather Service in San Juan.

The NHC said it expects four to six inches of rainfall on the island, with up to 10 inches in isolated areas, and warned of possible “life-threatening” flash floods and rip currents.