- Tropical Storm Barry is strengthening as it nears the central Louisiana coast. The storm is expected to develop into a Category 1 hurricane and make landfall this morning.
- A hurricane warning is in effect for parts of the state’s coast, including New Orleans.
- The storm could be the biggest test ever for New Orleans’s river levees along the Mississippi. Forecasters warn that the river may reach levels of 19 feet — the highest since 1950.
- New Orleans was hit with flash floods already this week, and the water is likely to keep rising: The National Weather Service has forecast up to 20 inches of rain in parts of Louisiana.
- As the planet and its oceans warm because of climate change, hurricanes are likely to get wetter and slower.
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Tropical Storm Barry is strengthening as it approaches the Louisiana coast. It’s expected to make landfall this morning near Morgan City.
Heavy rains are already battering the Gulf Coast, leaving more than 46,000 people in Louisiana without power. Coastal residents are also getting hit with flash flooding and 70-mph winds. The National Hurricane Center (NHC) still expects Barry to strengthen to a Category 1 hurricane (with sustained wind speeds 73 mph or above) before making landfall. It could bring a storm surge of up to 6 feet.
“The center of Barry will make landfall along the south-central Louisiana coast during the next several hours,” the NHC said at 7 a.m. local time, adding that up to 20 inches of rainfall could cause “dangerous, life threatening flooding over portions of the central Gulf Coast into the Lower Mississippi Valley.”
A hurricane warning is in effect for the stretch of coast from Grand Isle to Intracoastal City. A storm-surge warning is in effect for the area between Intracoastal City and Biloxi, Mississippi, as well as Lake Pontchartrain.
Tornadoes are also possible as a result of the storm.
If the storm does make landfall as a hurricane, it would be only the third time in 168 years (since researchers started keeping track) that a hurricane hits Louisiana in July, 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, and US President Donald Trump has also declared a state of emergency, authorizing federal agencies to coordinate disaster-relief efforts.
The biggest test of Mississippi River levees since 1927
The storm poses a significant threat to much 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 16.7 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. The river is expected to crest at a near-record height of 19 or 20 feet — 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.
“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 slower 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 due to 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 research from Yale Climate Connections.
Water temperatures in the Gulf of Mexico are at near-record levels, Holthaus wrote.
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.
What’s more, storms are also getting more sluggish. Over the past 70 years, the speed of hurricanes and tropical storms has slowed about 10% on average, according to a 2018 study. A slower pace of movement gives a storm more time to lash an area with powerful winds and dump rain, which can exacerbate flood problems.
That’s what happened with Hurricane Harvey, which stalled over Houston in 2017 and dumped unprecedented amounts of rain onto the city for days.
According to meteorologist John Kassell, Tropical Storm Barry is also expected to slow to a crawl for several hours after making landfall, which could contribute to life-threatening flooding that’s expected in southeast Louisiana.