The images of Laura's destruction in Santo Domingo 3:59
(CNN) - The Gulf Coast will be hit by a couple of hurricanes this week, bringing torrential rains, fierce winds and fierce storm surges.
Marco went from a tropical storm to a Category 1 hurricane on Sunday. It is estimated to make landfall off the Louisiana coast on Monday.
Then there's Tropical Storm Laura, which is also expected to become a hurricane before making landfall in the United States on Wednesday night or early Thursday, also on or near the Louisiana coast.
"The unprecedented issue here is that it is the same state 48 hours apart," said National Weather Service meteorologist Benjamin Schott.
"In modern meteorological history ... never before has there been anything like this where possibly two hurricanes struck miles apart over a 48 hour period."
The imminent threat of Hurricane Marco prompted mandatory evacuations Sunday in Plaquemines Parish, Louisiana, and Grand Isle, Louisiana.
And Marco and Laura's doublet means "there may not be much scope" for rescuers or power restoration teams to respond to casualties between the two storms, Louisiana Gov. John Bel Edwards explained.
'Life-threatening storm surge'
"Ultimately, the big concern will be storm surge," said CNN meteorologist Allison Chinchar.
The National Hurricane Center (NHC) has warned of a "potentially deadly storm surge" as Marco approaches the Gulf Coast.
The NHC issued a storm surge warning for coastal cities from Morgan City, Louisiana, east to Ocean Springs, Mississippi.
"A storm surge warning means there is a danger of life-threatening flooding from increased water moving inland from the coast for the next 36 hours," the hurricane center said.
Marco is expected to bring a storm surge height of 1.2 to 1.8 meters for Biloxi, Mississippi and Grand Isle, Louisiana, Chinchar said.
New Orleans at risk
"Since New Orleans is not on the coast, it will be more affected indirectly through Lake Pontchartrain, which is expected to have swell heights of 0.6 to 1.2 meters," Chinchar said.
That, combined with 4 to 6 inches of rain, means New Orleans could flood Monday.
"New Orleans is especially at risk because it is essentially shaped like a bowl," Chinchar said.
"Thanks to the drainage system they have installed, the city can act as a sieve, allowing the water to flow," he explained. "But when it rains a lot in a short period of time, the drainage system can get overwhelmed and that strainer acts more like a bowl and floods the city."
Marco and Laura will unload torrential rain
Tropical Storm Laura caused flooding Saturday in Salinas, Puerto Rico.
Marco is estimated to bring "an enormous amount of rain, not just to Louisiana, but to areas of Mississippi, Alabama and even Florida," Chinchar noted.
"Then you have Laura making her way to the Gulf, shortly after Marco makes landfall," he said.
"Even on Monday and Tuesday, Key West, Miami, would have some of those outer bands of Laura that will produce very heavy rains and very gusty winds," said Chinchar.
On Sunday Laura hovered over the Dominican Republic, "throwing a lot of rain there," she said.
By the time Laura reaches the coast of the United States, it is expected to be a Category 2 hurricane, with maximum sustained winds of at least 96 miles per hour.
Laura is expected to have an impact in many of the same areas that Marco will affect.
CNN Meteorologist Haley Brink contributed to this report.
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