Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

Louisiana Civil Air Patrol

It is difficult to know where to begin with the historic flooding in Louisiana during the past week. There is the sheer volume of water itself—based on rainfall accumulations, an estimated 4 trillion gallons of rain fell across southern Louisiana from the middle of Thursday through Saturday morning. That is roughly the same amount of water discharged by the Mississippi River into the Gulf of Mexico over the course of 80 days.

The rains hit hardest just to the east of Baton Rouge in Livingston Parish, which straddles Interstate 12 and is home to about 130,000 people. Some state officials have estimated that as many as 70 percent of the homes and businesses in this parish—more than 30,000 homes—were flooded. Across the state, officials say as many as 80,000 structures may have flooded. Some 20,000 people had to be rescued from flooded homes and vehicles. Very early damage estimates pegged the storm at $1 billion to $2 billion. At least seven people have died.

Area roadways were also hit extremely hard. The state's Department of Transportation and Development estimates that 30 state roads were washed out, and thousands of miles of state roads were under water as water levels rose on Sunday. Some 1,400 bridges will need to be inspected, as well. From Saturday through Monday large chunks of Interstate 10 and 12, which cross the southern tier of Louisiana, were closed due to floodwaters. As of Tuesday morning, parts of Interstate 10 remained closed due to flooding.

What was it?

So what caused this mess? It was an almost-tropical storm. For much of last week, forecasters at the National Hurricane Center watched a low-pressure system in the northeastern corner of the Gulf of Mexico, which eventually moved inland and slowly tracked westward over Florida, Alabama, Mississippi, and then Louisiana, where it eventually stalled out late last week over the southern part of the state. It had a warm core, like the low-pressure center of a tropical storm. However, by the time the storm looked most tropical on satellite, it had moved over land, and it lacked the surface wind speeds of 39mph or greater characteristic of a tropical storm. As The Weather Channel's hurricane specialist Greg Postel described the system, "It wasn't a tropical cyclone, but it was a cyclone that was tropical."

Perhaps because it was not named, and with the ongoing presidential election and unfolding drama at the Summer Olympics, the Louisiana storm did not garner a great amount of attention from the greater US public this weekend. But in scope it was easily the worst flooding disaster to hit Louisiana in more than a decade, since Hurricane Katrina crashed through the flood barriers in New Orleans.

During the three-day period from Thursday through Sunday morning, according to the National Weather Service, several locations in south-central Louisiana received in excess of 24 inches of rain. A handful of rivers, including the Amite and Tickfaw waterways, crested well above historical high water marks. The measured rain totals over Livingston and some of the surrounding parishes in southeastern Louisiana were the equivalent of a 1,000-year flooding event. "The observed rainfall totals were quite significant and rare," the Lower Mississippi River Forecast Center stated.

The role of climate change

Such storms are not unprecedented. A similar event unfolded in June 2001, when Tropical Storm Allison (which barely met the criteria for a named storm) developed in the Gulf of Mexico and moved inland over the Houston metro area. Six-day rainfall totals for the storm across most of Harris County were 20 to 40 inches, with about half of that coming during a single night and causing catastrophic flooding. Damages were estimated at $5 billion in the densely populated urban area—by far the costliest tropical storm ever to hit the United States.

It is a valid question to ask whether climate change plays a role in these kinds of inland flooding events. Areas of Louisiana and Texas, along the Gulf of Mexico and its rich source of tropical moisture, are already prone to heavy flooding. However, warmer temperatures can help to fuel storms, because warmer air is capable of containing more water vapor than cooler air, and therefore more moisture becomes available to fuel storms over time. This summer's much-above-average temperatures in July and August for the southern United States may therefore have exacerbated some of the flooding in Louisiana.

Listing image by Louisiana Civil Air Patrol