Clusters of severe storms rolling through the South since Memorial Day have caused widespread flash flooding in Texas and Louisiana. Cars stalled out and were abandoned on flooded highways in Houston and in a single day, rainfall deficits for parched southeast Texas were eliminated. Flights were grounded throughout area airports. According to measurements taken at Houston’s Hobby Airport, this is now the fifth-wettest May on record thanks to the last three days of rain.
In Louisiana, more than a foot of rain in just a few hours on Wednesday caused a dozen caskets to float away from their graves In Belle Rose. About 50 houses and apartments were flooded in St. Landry Parish, while In Ascension Parish, near Baton Rouge, at least 29 homes, three schools and two businesses were inundated. At least one man has drowned in the floods in Louisiana, after police believe he was swept under his car by powerful rising waters in a parking lot. In Lafayette, Louisiana, more rain fell on Wednesday than had fallen in the past three months combined.
In the latest National Climate Assessment, scientists listed an increase in heavy rainfall events as one of the most visible consequences the country will encounter as the climate changes. The southeast is expected to see a 27 percent increase in the amount of precipitation that falls in very heavy rainfall events — the heaviest one percent of events. These rainfall events often cause flash flooding as drainage systems are overwhelmed, and do little to alleviate drought, as soils are unable to absorb large quantities of water all at once.
This change in the distribution of precipitation can be explained through basic physics. As the world’s oceans and air warm up, more water is transferred from the ocean into the atmosphere. That’s because warmer water leads to more evaporation, and warmer air can hold more water. The air holds about 7 percent more moisture for every 1 degree Celsius increase in temperature. That moisture can then be concentrated into fronts, which unleash torrential downpours when they encounter disturbances in the air or land.
Earlier this spring, the southern and eastern portions of the U.S. were hit by devastatingly heavy rains with the panhandle of Florida and southern Alabama getting drenched by more than two feet of rain in 24 hours. On April 30, Pensacola, FL experienced its rainiest day ever recorded, receiving almost as much rain in 24 hours as L.A. has gotten since January 1, 2012. At least 300 people had to be rescued from the waters in Florida, with some people forced to climb up to their roofs or attics to escape the water, and at least one person died after driving a car into the floods. The flooding was the worst the area had seen in 30 years.