SAN JUAN, Puerto Rico (Washington Post) - Hurricane Maria roared ashore on Puerto Rico on Wednesday (Sept 20) as the strongest storm to strike the island in more than 80 years while panicked residents fled to high ground and huddled in shelters hoping to withstand powerhouse winds that have already left death and devastation across the Caribbean.

"On the forecast track, (Maria) would be the most destructive hurricane in Puerto Rico history," tweeted Mr Eric Blake, a forecaster at the Hurricane Centre.

Mr Michael Brennan, another Hurricane Centre forecaster, tweeted late on Tuesday that he was "starting to run out of adjectives for" Maria, the second huge hurricane to plow through the Caribbean this month. "Horrifying," Mr Brennan wrote.

Already, Maria has roared over islands to the east with winds of more than 257kmh and downpours that triggered flooding and landslides. In the French island of Guadeloupe, officials said at least two deaths were blamed on Maria, and at least two people were missing after a ship went down near the tiny French island of Desirade.

Maria's force was clear from its first brush with land. In a breathless series of Facebook posts late on Monday, the prime minister of the island nation of Dominica, Mr Roosevelt Skerrit, described furious winds that tore off the roof of his official residence. "My roof is gone. I am at the complete mercy of the hurricane. House is flooding," he wrote.

Puerto Rico was spared the full force of the Category 5 monster Irma earlier this month. Yet the storm came close enough to knock out power for about 1 million people on Puerto Rico and weaken its hurricane defenses.

"This is going to be an extremely violent phenomenon," Puerto Rican Governor Ricardo Rosselló told the Associated Press as Maria approached. "We have not experienced an event of this magnitude in our modern history."

Before dawn, Maria was 80.4km south-east of San Juan and churning to the north-west at 16.1kmh. Its maximum sustained winds of 249.4kmh were down slightly from late Tuesday. But that meant little for Maria's ability to threaten anything in its path.

"Maria is an extremely dangerous Category 4 hurricane... and it should maintain this intensity until landfall," the Hurricane Centre said.

The Hurricane Centre warned that the rain - possibly exceeding 63.5cm in some places - may "prompt numerous evacuations and rescues" and "enter numerous structures within multiple communities", adding that streets and parking lots may "become rivers of raging water" and warns some structures will become "uninhabitable or washed away".

Along the coast, the Weather Service describes"extensive impacts" from a "life-threatening" storm surge at the coast, reaching 6 to 9 feet above normally dry land. The highest storm surge is likely to occur just north and north-east of where the centre makes landfall, which could target south-east Puerto Rico.

Puerto Rico is very vulnerable to hurricanes, but it has been lucky as well. The last hurricane to make landfall was Georges in 1998. Just one Category 5 hurricane has hit Puerto Rico in recorded history, back in 1928. The last time a Category 4 storm struck the island was in 1932.

To the north, the remnants of Hurricane Jose brought pounding surf and 104.6kmh winds to southern New England. Tropical storm warnings were issued for the coast from Rhode Island to Cape Cod.

Jose was also watched closely for its spillover effect on Maria. It could help in keeping Maria away from the US mainland by drawing it to the north-east. However, if Jose weakens too quickly, Maria could drift closer to the US coast by the middle of next week.

Residents of San Juan, the capital city, appeared to be heeding officials' warnings to get ready, with many preparing since the weekend with a growing sense of unease and resignation.

At a gas station in Barrio Obrero, Mr Manuel Rivera sat huddled in the back of a red Jeep on Tuesday afternoon surrounded by water jugs full of gas.

His friends filled them one by one to ensure they would have enough fuel for the generator at their home. They had electricity for now, but they expected it could be gone by nightfall.

"The power leaves when it wants to," Mr Rivera said. After Irma, his home was without power for about a week.

Grocery and convenience stores had run out of water and ice. Neighbourhoods were quiet, save for a few cars on the roads and the sound of people banging boards across their windows.

"Of course I'm nervous, but I feel prepared," said Mr Wilfredo Torres, 36, one of the men installing corrugated steel storm windows outside the post office in the Miramar neighbourhood. "There's another storm coming. Maria is coming, and there's nothing you can do. You have to prepare and then wait and see."

A family from Bayamon braved the winds for a brief walk along Avenida Munoz Rivera on the waterfront, bored after being cooped up in their house all day setting up for the hurricane.

"Everyone is calm but tense," said Mr Jorge Velez, out with his wife, Ms Arleen Santini, and their son, Ricardo, 6. "I've seen David, Hugo and Ortensia. But what Maria brings is double the force."

With that, drops began to fall from the sky, and the strengthening winds tilted the palm trees along the waterfront.

Mr Velez and his family rushed to their white SUV, dodging the rain and heading back home for the night.

Fear also rippled across Vieques, a tiny island off Puerto Rico's east coast that is home to about 9,500 residents, many of whom live below the poverty level and are accustomed to dealing with some measure of hardship. Many there evacuated during Irma and opted to stay put for Maria but are now having second thoughts.

"I regret not leaving," said Ms Marie Rivera, 56, whose parents live on Puerto Rico's main island. "I'm not sure when I will be able to see my family again. I'm starting to get a little anxious now."

Irma left many here without power for days. In an unfortunate twist, some residents of Vieques had stocked up on critical supplies in advance of Irma only to donate what they had left to harder-hit areas such as Tortola and St. Thomas. Residents rushed to restock before deliveries to the island stopped and the power flickered off yet again.

President Trump on Sunday declared emergencies in the US Virgin Islands and Puerto Rico in advance of Maria.

The Federal Emergency Management Agency has embedded workers across the US territories in the Caribbean, including in parts of the US Virgin Islands affected by Irma, to ensure residents have food and water before the storm.

The US military is expected to assist Puerto Ricans after the storm hits, but is mostly steering clear beforehand to avoid being caught up in it and unable to help, military officials said.

Recovery efforts in Puerto Rico could be hampered by long-standing financial problems that led the territorial government to file for a form of bankruptcy in May.