Historic August 2016 Flooding in Louisiana After 2+ Feet of Rain Sends Rivers to Record Levels (RECAP)

(NEWS + PHOTOS: Evacuations, Rescues as Deadly, Torrential Rains Flood Louisiana, Mississippi)

At least four locations in Louisiana saw more than 2 feet of rain, with the highest amount being 31.39 inches near Watson. Record flooding was observed on at least eleven river gauges in Louisiana.

(MORE: Before and After Images of the Flood)

Historic Flooding Recap

Here are some of the notables about this flood event.

Rainfall Totals

The highest storm total report was 31.39 inches near Watson, Louisiana, according to NOAA.

This total was higher than from any tropical cyclone or remnant in Louisiana since 1950, though an August 1940 hurricane wrung out 37.50 inches on Miller Island, according to NOAA/WPC forecaster and tropical cyclone rainfall guru, David Roth. 

Here are some additional totals from NOAA: 

• 27.47 inches near Brownfields, Louisiana
• 24.75 inches near Denham Springs, Louisiana
• 22.84 inches near Gloster, Mississippi
• 21.60 inches at Lafayette, Louisiana
• 19.14 inches in Baton Rouge, Louisiana (Record daily rainfall on Friday and Saturday)
• 14.43 inches in Panama City, Florida

Lafayette, Louisiana, had two consecutive days with 10 inches or more of rainfall Aug. 12 and Aug. 13. Prior to that, dating to 1893, that happened only one other day in Lafayette.

River Levels

At least 11 river gauges saw record crests in Louisiana, some by a large margin. Here's a recap:

• Comite River at Comite Joor Road: Record crest set by 3+ feet on Aug. 14
• Comite River near Olive Branch: Record crest set on Aug. 13
• Amite River at Magnolia: Record crest set by 6+ feet on Aug. 13
• Amite River at Denham Springs: Record crest set by nearly 5 feet on Aug. 14
• Amite River Basin at Bayou Mancha Near Little Prairie: Record crest set on Aug. 14
• Amite River at Bayou Manchac Point: Record crest set on Aug. 14
• Amite River at Port Vincent: Record crest set by almost 3 feet on Aug. 14
• Amite River at French Settlement: Record set on Aug. 14
• Tangipahoa River at Robert: Record crest set on Aug. 13
• Tickfaw River at Holden: Record crest set on Aug. 13
• Tickfaw River at Liverpool: Record crest set on Aug. 12

The Vermillion River at Lafayette, Louisiana, crested at its highest level since an August 1940 hurricane, about 7.5 feet above flood stage and about 6 feet above the March 2016 flood.

How the Flood Happened: Described as "Like an Inland Tropical Depression"

Deep, tropical moisture in combination with low pressure near the earth's surface and aloft were the main ingredients that fueled the serious flooding in Louisiana and adjacent parts of southwest Mississippi.

On the morning of Aug. 12, NOAA's Weather Prediction Center said this when talking about the heavy rain event: "The best description of this system is that of an inland sheared tropical depression."

The rainfall it produced was indeed very similar to what one would expect from a slow-moving tropical depression or storm since rainfall potential is related to the forward speed of those types of systems.

Rainfall totals in the double digits from slow-moving tropical depressions or storms can wreak extreme havoc on a region. Rivers can rise rapidly and easily exceed flood levels by a wide margin, inundating homes and businesses and in some cases making travel impossible. We saw all of that happen in Louisiana and southwest Mississippi.

(MORE: Tropical Storms Can Be Destructive and Deadly)

More evidence for how this situation was similar to an inland tropical depression is the amount of moisture that was in the atmosphere.

A weather forecast discussion from the National Weather Service in New Orleans on Aug. 12 said that the moisture content in the atmosphere was higher than what has been observed there during some tropical cyclones. It was even close to an all-time record for the area, they added.

When that much moisture is available in the atmosphere, thunderstorms can produce excessive rainfall of several inches in a single hour, leading to astronomical totals over time.

While no one likely forecasted 24+ inches of rain ahead of this event like we saw in southeast Louisiana, this is the type of thing that can happen on a very localized scale in situations like this one.

The moisture was pulled in by the aforementioned surface low pressure system which actually intensified as it moved from near the Alabama coast to northwest Louisiana Aug. 11-13, according to Dr. Jeff Masters of wunderground.com. 

PHOTOS: Louisiana, Mississippi Floods - August 12-13, 2016