San Juan, Puerto Rico — The National Hurricane Center issued a hurricane watch and tropical storm warning for Puerto Rico early Tuesday as Tropical Storm Dorian moved through the Windward Islands. Also early Tuesday, the Dominican Republic government issued a hurricane watch for some parts of the island and a tropical storm watch for portions of its north and south coasts.

The hurricane center, in Miami, recommended that residents of the Virgin Islands keep an eye on Dorian, as well. The center said that, as of 2 p.m. EDT Tuesday, the storm had maximum sustained winds of 50 mph and was forecast to strengthen over the next 48 hours as it moved toward Puerto Rico.

Dorian's center was some 370 miles east-southeast of Ponce, Puerto Rico, and about 70 miles west-northwest of Martinique. The storm was moving west-northwest at 13 mph. Tropical-storm-force winds extended outward up to 45 miles from the center.

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"Slow strengthening is forecast during the next 48 hours, and Dorian is forecast to be near hurricane strength when it moves close to Puerto Rico and eastern Hispaniola," the center said.

Tropical Storm Dorian was pictured off the coast of Venezuela in this August 26, 2019, NASA satellite photo. NASA

The center said tropical storm warnings for Martinique, St. Vincent, the Grenadines and St. Lucia were discontinued. Tropical storm watches were in effect for Saba and St. Eustatius, and tropical storm watches were discontinued for Dominica and Grenada.

A tropical storm warning means tropical storm conditions are expected within 36 hours while a tropical storm watch means tropical storm conditions are possible within 48 hours.

The storm was expected to dump between 3 to 8 inches of rain on the Windward islands, with isolated amounts up to 10 inches. The hurricane center said the rainfall "may cause life threatening flash floods, especially where totals exceed four inches."

Nearly empty shelves that normally have bottled water are seen at a grocery store as Tropical Storm Dorian approaches Cabo Rojo, Puerto Rico, on August 26, 2019 Reuters

In Puerto Rico, people crowded into grocery stores and gas stations to prepare for Dorian, buying food, water and generators, among other things.

Many were worried about power outages and heavy rains on an island still struggling to recover from Hurricane Maria, a Category 4 storm that hit in September 2017. Some 30,000 homes still have blue tarps as roofs and the electrical grid remains fragile and prone to outages even during brief rain showers.

On Monday, Puerto Rico Governor Wanda Vázquez signed an executive order declaring a state of emergency and provided a list of all the new equipment that public agencies have bought since Maria.

"I want everyone to feel calm," she said. "Agency directors have prepared for the last two years. The experience of Maria has been a great lesson for everyone."

She said public schools would close Tuesday afternoon and that at least one cruise ship canceled its trip to Puerto Rico. She said those without a proper roof can stay in one of the 360 shelters around the island.

In St. Lucia, Prime Minister Allen Chastanet announced that everything on the island of nearly 179,000 people would shut down Monday evening. "We are expecting the worst," he said.

Joannes Lamontagne, who lives in the island's southwest region, said by phone that everything at his hotel, Serenity Escape, was already protected.

"I don't wait until it's announced," he said of the storm. "We're always prepared no matter what."

The government of Barbados urged residents of the eastern Caribbean island to remain vigilant even though Dorian appeared to have done little damage as it headed toward the northern Windward islands and Puerto Rico. The government discontinued its tropical storm warning that was up.

Much of Barbados shut down Monday as Dorian approached and authorities urged residents to remain indoors amid reports of electrical outages and other minor incidents.

Also early Tuesday, what the hurricane center described as a poorly organized tropical depression was drifting southeast between the southeast U.S. coast and Bermuda. It was located about 365 miles southeast of Cape Hatteras, North Carolina, and was moving southeast at 2 mph with maximum sustained winds of 35 mph. It was expected to become a tropical storm Tuesday night.