LOUISIANA — After slamming Cuba twice in less than 24 hours, Hurricane Ida is expected to rapidly strengthen before pummeling Louisiana on Sunday, forcing evacuations in New Orleans and the surrounding coastal region on the eve of the 16th anniversary of Hurricane Katrina.

On Saturday morning, Ida was moving away from Cuba and into the Gulf of Mexico, where it is expected to intensify over the next 24 to 36 hours prior to landfall across the Louisiana coast on Sunday afternoon or evening. Recent satellite imagery showed the storm is becoming better organized.

Ida is anticipated to reach at least Category 4 strength before landfall, the National Hurricane Center said, maintaining its earlier forecast.

"Ida is expected to be an extremely dangerous major hurricane when it approaches the northern Gulf Coast on Sunday," National Hurricane Center forecasters said Saturday morning. At 8 a.m. ET, the storm sustained winds of 85 mph.

Officials throughout the state implored people to evacuate, with some issuing mandatory orders to do so. News footage from the area showed traffic backed up heading out of New Orleans.

In text alerts Saturday, New Orleans officials urged residents to "leave by this morning if you can."

"If you're staying, gather supplies, charge devices, lower fridge temp & secure outdoor items today," the message said.

State officials also texted residents: "Get ready for Ida."

"Louisianans have until nightfall," the text warned, adding that Ida will "bring serious impacts across the state."

New Orleans Mayor LaToya Cantrell issued a mandatory evacuation of all city areas that are outside its flood protection system, and urged other residents to evacuate voluntarily or shelter in place.

"The city cannot issue a mandatory evacuation because we don't have the time," Cantrell said Friday at a news conference, speaking about areas inside the levee system. "We do not want to have people on the road, and therefore, in greater danger because of the lack of time."

A dangerous storm surge of 10 to 15 feet is expected from Morgan City, Louisiana, to the mouth of the Mississippi River on Sunday as Ida makes landfall, the NHC said.

The storm surge, coupled with winds as strong as 150 mph, could leave some parts of southeast Louisiana "uninhabitable for weeks or months," according the to the latest hurricane statement from the National Weather Service in New Orleans.

The statement warned of "structural damage to buildings, with many washing away" as well as winds that could bring "widespread power and communication outages."

Flooding rains could cause "numerous road and bridge closures with some weakened or washed out" along with "some structures becoming uninhabitable or washed away."

Hurricane conditions are likely in areas along the northern Gulf Coast beginning Sunday, with tropical storm conditions expected to begin by late Saturday night or early Sunday morning. These conditions will spread inland over portions of Louisiana and Mississippi Sunday night and Monday.

Rainfall can amount to 8 to 16 inches, with isolated maximum totals of 20 inches possible across southeast Louisiana and southern Mississippi through Monday — which will likely lead to significant flash and river flooding impacts.

A hurricane warning remains in effect from Intracoastal City, Louisiana, to the mouth of the Pearl River and includes Lake Pontchartrain, Lake Maurepas and New Orleans.

In Louisiana, a tropical storm warning was in effect from Cameron to west of Intracoastal City and the mouth of the Pearl River to the Mississippi-Alabama border. Tropical storm warnings and watches are also issued stretching east to the Alabama-Florida border.

The city is anticipating impacts from damaging winds of up to 110 mph, according to Collin Arnold, director of the New Orleans Office of Homeland Security and Emergency Preparedness.

If Ida makes landfall in Louisiana, it would be the fourth hurricane to do so since last August and Louisiana's third major hurricane landfall in that span.

Sunday, which is the forecast landfall day, is also the 16th anniversary of Hurricane Katrina, a devastating Category 3 storm with winds near 127 mph that caused severe flooding to cities along the Gulf Coast, from New Orleans to Biloxi, Mississippi.

More than 1,800 people were killed in the Gulf region directly or indirectly from the storm and in the days after, according to a NOAA report.

"August 29 is an important date in history here," Collins told CNN Saturday. "A lot of people remember what happened 16 years ago. It's time to hunker down tonight and be where you need to be."

In Washington, an administration official told CNN that President Joe Biden is "being briefed regularly on the storm's trajectory." Biden spoke with the governors of Louisiana, Alabama and Mississippi on Friday.

Hospitals in New Orleans will not evacuate and instead shelter in place while Ida makes its way through the region, the city's health department director Dr. Jennifer Avegno said.

Capacity at nearby hospitals in Texas and Florida is "extremely limited," Avegno said, as COVID-19 hospitalizations are on the rise. She added that the city's hospitals are familiar with plans during storm season.

"I would ask our residents, if you do not need to go to the hospital this weekend, if you do not have a life-threatening emergency, please do not go," Avegno said. "This is not the time to go to the hospital for a routine thing that could wait until later."

Before entering the Gulf, Ida made landfall twice over Cuba as a Category 1 hurricane. First forming as a tropical storm in the Caribbean on Thursday, Ida hit Cuba's Isla de la Juventud, or Isle of Youth, on Friday afternoon, the US National Hurricane Center said.

A second landfall occurred in western Cuba around 20 miles (30 km) east of La Coloma, according to satellite images, radar data and NOAA Hurricane Hunter data.

More than 4 inches of rain were recorded in Pinar del Rio, according to the Cuban Meteorological Institute. Jagüey Grande Matanzas experienced around 2.4 inches of rain and the Isle of Youth had 1.89 inches, the institute said. Havana recorded 0.94 inches.

Isolated instances of 5 to 15 inches of rain in some parts of western Cuba are expected, according to hurricane center forecasters.

"These rainfall amounts may produce life-threatening flash floods and mudslides," the hurricane center said. Swells generated by Ida are expected to affect the western part of the island through Saturday morning. — CNN