Texas coastal residents urged to leave in 'strongest possible terms' as Hurricane Harvey intensifies in the Gulf

— -- The National Hurricane Center has issued an advisory instructing Texas residents along the Gulf of Mexico coast to "rush" their storm preparations as Hurricane Harvey "rapidly" intensifies.

All preparations for residents along the middle Texas coast should be completed today, the National Hurricane Center said. The storm is expected to make landfall around 1 a.m. Saturday.

The coastal city of Corpus Christi has so far not implemented mandatory evacuations, but Mayor Joe McComb called for people to leave in the "strongest possible terms."

“We could mandate it but people have to make a decision on their own," McComb said.

The state announced mandatory evacuations for seven counties: Calhoun County, San Patricio County, Refugio County, Brazoria County, Jackson County, Victoria County and Matagorda County. Nueces County, where Corpus Christi resides, has not received an evacuation order.

Most of the flights in and out of Corpus Christi International Airport for Friday have been canceled, according to FlightAware.

United Airlines will operate its last flight out of Corpus Christi at 7 a.m. Friday, and Southwest Airlines will operate its last flight at 10:40 a.m., the airport announced on Facebook.

Police and fire personnel will bunker down during the storm and will likely not be able to provide emergency services, Corpus Christi Police Chief Mike Markel said.

All non-essential personnel and their families have been ordered to evacuate from the Naval Air Station in Corpus Christi and the Naval Air Station in Kingsville, which are both training air bases. The stations are in the process of moving aircraft -- some to hangers and some to the Naval Air Joint Reserve Base in Fort Worth.

Three Air Force Reserve C-5 transport planes have been moved from the Lackland Air Force Base in San Antonio to Biggs Army Airfield in Fort Bliss. There are plans to move four additional C-5s tomorrow, but that plan could be adjusted depending on the storm. The Coast Guard said shallow-draft vessels capable of making rescues in flooded urban areas are en route to Texas and Louisiana.

The Coast Guard also upgraded the alert status in local ports to "yankee" -- which means inbound ships must seek alternate ports and certain ships looking to leave port must do so by 10 a.m. on Friday.

Louisiana Gov. John Bel Edwards issued a statewide emergency declaration ahead of Hurricane Harvey, saying there is potential for it to move back into the Gulf of Mexico and hit Louisiana after it makes landfall in Texas.

A spokesperson for FEMA said the state is working with the city of New Orleans to make sure its drainage pumps are working. The state has no plans to issue evacuation orders at this time.

The outer bands of the storm are expected to bring 7 to 10 inches of rain to southwest Louisiana, Edwards said. The National Guard there has purchased more than 500,000 sandbags to prepare, he said.

As of 4 a.m. CT, the hurricane was about 180 miles southeast of Corpus Christi. The NWS upgraded Harvey to a category 2 storm, with maximum sustained winds of 105 mph, at 4 a.m. local time on Friday. It was moving north-northwest at 10 mph, according to the National Hurricane Center.

The hurricane is expected to hit Texas as a Category 3 storm, forecasters say. The state hasn't been hit by such a powerful storm since Hurricane Bret in 1999.

Harvey may cause a life-threatening storm surge of up to 12 feet, with waves as high as 20 feet along the Texas coast. Perilous flash flooding and 115 mph gusts of wind are also possible.

How to prepare for the hurricane

Before the storm

When prepping for a hurricane, it's important to "hide from the wind and run from the water," National Hurricane Center meteorologist Daniel Brown told ABC News earlier this month.

Emergency managers are encouraging residents who may be affected by the hurricane to monitor the weather forecast for their area and listen to the directives given by emergency officials, said Lt. Craig Cummings, spokesperson for the Texas Department of Public Safety in Houston.

Cummings encouraged people to have an emergency kit with essentials such as important documents, medications and supplies, including food, water, batteries, a flashlight and a battery-powered radio.

Some stores in Corpus Christi are already running out of supplies.

"We're out of bread and we're out of water right now," Julie Canales, an employee at the claims department in the Corpus Christi Sam's Club, told ABC News. "We’ve been stocked every day, but as soon as we get it it’s gone within an hour between truck [deliveries]."

Coastal Hardware in Corpus Christi has already run out of sand bags and kerosene lanterns, store manager Jennifer Wimsett told ABC News. People are improvising by buying topsoil and filling up trash bags with them, she said.

It is also important to have a paper map for after the storm passes in case cell phones service goes down and people traveling are forced to take unfamiliar routes due to the flooding.

During the storm

Residents should fill bathtubs and other large containers with water to help with washing or filling toilets in case the water is shut off, according to safety tips recommended by Farmers Insurance.

During the storm, people should stay indoors and away from windows and glass doors. At the height of the storm, seek shelter in an interior room, according to the insurance company's tips.

The company also recommends that people who live in temporary structures like mobile homes or in high-rise building be prepared to evacuate.

After the storm

Drivers should not venture into flooded waters, Cummings said. It only takes about 2 feet of water for a car to be swept away in floodwaters and only about two inches of water to for an adult to be swept away, he said.

About 50 percent of all flash flood fatalities nationwide involve vehicles, according to Cummings.

"If someone is in an area that is beginning to flood, it's essential that they get to higher ground and be looking for an evacuation route out of the area," he said.