Hurricane Harvey makes landfall in Texas

Hurricane Harvey has slammed into the Texas coast as a Category 4 storm with winds of up to 130 miles per hour, the most powerful storm in over a decade to hit the mainland United States.

The hurricane made landfall between Port Aransas and Port O'Connor around 10pm local time and is expected to dump around one metre of rain along the Texas coast and parts of Louisiana as it lingers for days.

While thousands fled the expected devastating flooding and destruction, many residents defied mandatory evacuation orders and stocked up on food, fuel and sandbags.

"We're suggesting if people are going to stay here, mark their arm with a Sharpie pen with their name and Social Security number," Rockport Mayor Pro Tem Patrick Rios told reporters Friday, according to media reports.

"We hate to talk about things like that. It's not something we like to do but it's the reality. People don't listen."

As many as 5.8 million people were believed to be in the storm's path, as well as the heart of America's oil refining operations. The storm's impact on refineries has already pushed up gasoline prices.

As a Category 4 hurricane on the Saffir-Simpson scale, Harvey could uproot trees, destroy homes and disrupt utilities for days.

It is the first major hurricane to hit the mainland United States since Hurricane Wilma struck Florida in 2005.

Donald Trump, facing the first large-scale natural disaster of his presidency, said on Twitter he signed a disaster proclamation which "unleashes the full force of government help" shortly before Harvey made landfall.

In Corpus Christi, a city of 320,000 under voluntary evacuation, strengthening winds buffeted the few trucks and cars that continued to circulate on the streets.

The storm toppled wooden roadwork signs and littered the streets with pieces of palm trees as white caps rocked sailboats in their docks.

The NHC's latest tracking model shows the storm sitting southwest of Houston for more than a day, giving the nation's fourth most populous city a double dose of rain and wind.

"Life-threatening and devastating flooding expected near the coast due to heavy rainfall and storm surge," the NHC said.

Louisiana and Texas declared states of disaster, authorizing the use of state resources to prepare.

The city of Houston warned residents of flooding from close to 20 inches (60 cm) of rain over several days.

Houston Mayor Sylvester Turner advised city residents not to leave en masse, saying "no evacuation orders have been issued for the city." Chaotic traffic from a rushed evacuation in 2005 with Hurricane Rita proved tragic. "Calm and care!" he said in a tweet.

Thousands stranded on cruise ships

Cruise ships carrying thousands of passengers were stranded in the Gulf on Friday as Hurricane Harvey, a Category 4 storm, came ashore in the middle of the Texas coast, closing the Port of Galveston.

Carnival Corp said that three of its ships were unable to return Galveston as scheduled and that two of them would be forced to divert instead to New Orleans, where they would pick up fresh supplies.

The cruise line said passengers could get off those two ships in New Orleans but advised against that in a statement posted on its Facebook page.

"Given the severity and projected path of the storm along with potential challenges guests may encounter attempting to travel back to Galveston independently, we are strongly encouraging them to remain on board as we intend to return the ships to Galveston as soon as feasible," Carnival said.

A third ship, the Carnival Breeze, will extend its stay in Cozumel, Mexico, and begin sailing back to Galveston this weekend, the company said.

The next scheduled cruises on all three ships will be shortened and customers will receive refunds, the company said.

"We will continue to remain in close contact with port officials regarding their plans to re-open once the storm has passed," spokeswoman Christine de la Huerta said.

Royal Caribbean International said that its Liberty of the Seas cruise ship had departed Cozumel, Mexico on time on Friday and was still scheduled to return to Galveston on Sunday.

"However, we will return to Galveston only when it is safe to do so," Royal Caribbean spokesman Owen Torres said.

The port's interim director, Peter Simons, told the Houston Chronicle newspaper that officials there were still trying to determine if ships could safely return on Sunday.

"We're working with the cruise lines, the Coast Guard and the pilots to see what can be done to bring the cruise ships in as quickly but as safely as possible," Simons told the paper.

The Chronicle reported that a total of 1.73 million passengers left on cruises in 2016 from the port at Galveston, where an expanded cruise terminal opened last year.