Hurricane Safety and Preparedness

Potential Gulf Coast Landfall Could Be a Rainfall Flood Disaster

At a Glance

Any excessive rainfall along the Gulf Coast could lead to serious flooding concerns.
Depending on the track of 99-L, the drought-stricken Southeast could finally pick up some much-needed rain.

Invest 99-L may be several days away from any impact to the United States, if at all, but one potential impact may turn serious, regardless of the ultimate intensity of this tropical cyclone wannabe: flooding from heavy rainfall.

(MORE: Invest 99-L Forecast)

A sizable swath of the Gulf Coast has been soaked with heavy rainfall recently, first and foremost, the catastrophic flooding in southern Louisiana.

In just a few days' time, parts of Louisiana received over 30 inches of rain. Through Aug. 23, it has been the wettest August on record in Baton Rouge, with 27.23 inches of rain. It's the second-wettest August for Lake Charles and the third-wettest for New Orleans.

(MORE: Why the Louisiana Flood Happened, And 4 Other Things to Know)

August 2016 rainfall along the north-central and western Gulf coast through August 25. — August 2016 rainfall along the north-central Gulf Coast through August 25, 2016.
(Data: NWS)

But it's not just Louisianans who've been inundated with rain lately. Parts of central and southeastern Texas are also pacing toward a top-5 wettest August on record, through Aug. 23.

For Austin, it's currently the third-wettest August, with 6.58 inches of rain through Aug. 23. For Houston, it's the fourth-wettest, with 9.14 inches.

Farther to the east, over a foot of rain has fallen in Pensacola through Aug. 23, making it the eight-wettest August there. Cross City, Florida, has received over 15 inches of rain for the month and is currently experiencing its second-wettest August.

August 2016 rainfall along the northeast Gulf Coast through August 25, 2016.
(Data: NWS)

In South Florida, Naples is currently experiencing its wettest August on record, with 13.39 inches of rain through Aug. 23. Miami has already picked up over 10 inches of rain this August, making it their eight-wettest August on record.

Since virtually the entire Gulf Coast is already saturated from recent heavy rains, any additional big rain events, such as what we might see from this current system, would quickly trigger flash flooding.

According to National Weather Service's flash flood guidance, all it will take is 2 1/2 to 4 inches of rain in six hours or less to cause a flash flood along the Gulf Coast states. Invest 99-L, or potentially Tropical Storm or Hurricane Hermine, would likely produce much greater totals than that over a six-hour period.

(MORE: 3 Things We Know About Invest 99-L and 3 Things We Don't Know Yet)

Good News for the Southeast Drought Area?

While the excessive rainfall may be bad for areas along the Gulf Coast, 99-L or Hermine (or its remnants) could bring much-needed rainfall to the drought-stricken Southeast.

Drought relief, if any, would be dependent on the exact track of this system, which still remains uncertain.

Southeast Drought Monitor. Red areas indicate areas of extreme drought, the second-worst drought classification.
(USDA/National Drought Mitigation Center)

Parts of northeastern Alabama, northern and western Georgia and west-central South Carolina are currently in an extreme drought, the second-worst category, according to the National Drought Mitigation Center.

Flash flooding would still be possible in these areas if too much rain falls too quickly, so residents of the Southeast also need to monitor the forecast closely over the next several days, but the good news is that this rain would help alleviate the drought conditions this summer has brought.

Now is the time to prepare or refresh your hurricane plan, before the next storm strikes.

MORE ON WEATHER.COM: Louisiana, Mississippi Floods