Would-be Tropical Storm Barry is still a day or more away from forming, let alone making landfall. But the developing system’s impacts are already being felt on Wednesday morning in New Orleans.
Residents of the Big Easy woke up to tornadoes and water spouts touching down in the city and on Lake Pontchartrain, and to heavy rain. The National Weather Service also issued a flash flood emergency—the most severe form of warning—for the city, as well as watches along portions of the Louisiana Gulf Coast as trains of thunderstorms rippled over the area. The rain is already backing up sewers and flooding streets in the city below sea level, and the flooding crisis could worsen as soon-to-be Tropical Storm Barry ramps up.
As of late morning, rain gauges that are part of Weather Underground’s network have picked up 10 inches of rain on Wednesday alone. Those are unofficial measurements, but the scenes emerging out of New Orleans show large portions of the city flooded out. That includes the iconic French Quarter and Lower Garden District, relatively “high” neighborhoods that sit 2-3 feet above sea level, as well as neighborhoods sitting closer to or below sea level like the Bywater. The flash flood emergency issued by the National Weather Service extends north and west of the city with the agency warning that “[t]his is a life threatening situation. Seek higher ground now!”
While the floodwaters are obviously an extremely worrisome situation, reports of at least one waterspout and a tornado are adding to the weather-fueled calamity. The University of New Orleans tweeted that a tornado had touched down on campus and office workers and commuters with a view of Lake Pontchartrain caught site of a waterspout roaring across open water.
All of this is part of a series of storms that ripped across the Midwest, hit the Gulf of Mexico and are now forming into a tropical cyclone. The National Hurricane Center gave the currently organizing area of thunderstorms a “near 100 percent” chance of becoming a tropical cyclone in the next 48 hours and is likely to be a hurricane by Friday. The storm will have ample opportunity to ramp up as it feeds on the warm waters of the Gulf of Mexico while lumbering west.
The initial forecast from the National Hurricane Center is calling for 6-12 inches of rain with locally higher amounts of up to 18 inches. Right now, New Orleans is on the edge of the cone of probability for where the storm will likely make landfall, which is likely somewhere to the west (there’s also the caveat that the track can shift in the coming days). But that actually puts the city in a dangerous place since rain is likely to keep falling as the storm mirrors the coast before turning northward. The strongest storm surge usually forms on the northeast quadrant of tropical cyclones, which is right where the city sits according to the current forecast. Right now, the National Hurricane Center is calling for 3-5 feet of storm surge and watches have gone up for New Orleans and other parts of Louisiana’s coastline.
Couple the surge with the days of heavy rain ahead and already swollen Mississippi River still discharging this spring’s Midwest floodwaters and you have a dangerous recipe for compound flooding. That’s what happened during Hurricane Florence last year when heavy rains fell inland in North Carolina while up to 9 feet of storm surge pushed into the coast, backing up rivers. The one-two punch meant standing water with nowhere to go.
Climate change is both pushing seas higher and churning the hydrological cycle into overdrive with more extreme rain events. What’s likely to unfold along the Gulf Coast in the coming days is a prime example of both of these phenomenon and the nasty ways they can interact. As of Wednesday morning, the Mississippi River in New Orleans is forecast to crest on Saturday at 20 feet. The levees that separate the city from the river stand at an average height of 20 feet. Katrina tested the storm surge levees with catastrophic results. Now potential Barry and the spring flooding will test the city’s river flood protection in a way it hasn’t been tested. This is a dire situation, and one that’s playing out not just in New Orleans but across the U.S. with increasing regularity.
“We have had high-water events in hurricane season but we’ve never had an elevation forecast like this,” Army Corps of Engineers spokesman Ricky Boyett told NOLA.com.