A tropical storm over the Gulf of Mexico is moving toward the Louisiana coast.
The storm, named Barry, is expected to bring storm surge, heavy rainfall, and wind hazards to the central Gulf Coast over the next few days. It could develop into a Category 1 hurricane by Friday or Saturday and is forecast to make landfall on Saturday morning. For now, maximum sustained wind speeds hover around 40 mph, and the storm is 90 miles southeast of the mouth of the Mississippi river, heading west toward Louisiana.
On Wednesday, New Orleans saw up to 9 inches of rain because of the weather pattern, forcing the National Weather Service (NWS) to declare a flash-flood emergency. Traffic ground to a halt, and New Orleans residents were forced to wade through calf-deep water.
As of 5 p.m. ET on Thursday, the National Hurricane Center (NHC) has issued a hurricane warning for the stretch of coast from Grand Isle to Intracoastal City (which includes New Orleans). A storm-surge warning is in effect from the mouth of the Atchafalaya River to Shell Beach.
If the storm makes landfall this weekend as a hurricane, it would be only the third time in the past 168 years (since researchers started keeping track) that a hurricane hits Louisiana in July, the meteorologist Eric Holthaus wrote in the New Republic. Typically, August and September are peak hurricane season in the Gulf.
Louisiana Gov. John Bel Edwards declared a state of emergency in anticipation of the storm, which could dump as much as 20 inches (approximately 76 centimeters) of rain in the state over the coming days, according to the NHC.
The biggest test of Mississippi River levees since 1927
The storm poses a significant threat to the city of New Orleans, since the Mississippi River, which snakes by the city, has been continuously flooding the surrounding land since January. The water is sitting at a height of 16 feet.
New Orleans has levees in place to keep the river from flooding its banks and swamping nearby neighborhoods. But those levees are only 20 feet high in some places. As of Wednesday, the river was forecast to crest at a near-record height of 19 or 20 feet by Friday afternoon. If that happens, it’d be the highest level the Mississippi has reached in New Orleans since at least 1950, according to the NWS.
In 2005, Hurricane Katrina — one of the deadliest storms in US history — killed more than 1,800 people when storm-surge levees along canals in New Orleans failed. The Mississippi River levees, which were built in 1927, stayed intact during that storm. But this week might prove to be their biggest test ever. Edwards warned that there could be “a considerable amount of overtopping” of levees in Plaquemines Parish, a suburban district southeast of New Orleans.
“Right now 19 feet is the official forecast, and we can manage that,” David Ramirez, the chief of water management for the Army Corps of Engineers’ New Orleans District, told Slate on Tuesday.
But Ramirez added that his team is closely monitoring the lowest points of the levees.
“The levees protect the city up to 20 feet, but 19 is close and doesn’t include waves splashing up and so on. It’s too close for comfort for us. And that surge could be more or could be less,” he said. “If things change and it gets higher, at some point, there’s only so much we can do.”
We’re likely to see more frequent and wetter hurricanes
This past year was the hottest on record for Earth’s oceans and the fourth warmest for the planet.
As ocean temperatures continue to increase, we’ll likely see more coastal flooding because of sea-level rise (since water, like most things, expands when heated) and more severe hurricanes. That’s because a hurricane’s wind speed is influenced by the temperature of the water below. A 1 degree Fahrenheit rise in ocean temperature can increase a storm’s wind speed by 15 to 20 mph, according to Yale Climate Connections.
Water temperatures in the Gulf of Mexico are at near-record levels, Holthaus wrote.
What’s more, as the planet keeps warming, Earth’s atmosphere will be able to hold more moisture. That increases the likelihood of intense rainfall in already wet areas, according to Holthaus.