# August 2023 mid-south U.S. floods

In a three-day period from August 2–4, 2023, significant flooding occurred across northwestern Tennessee, southwestern Kentucky, and southeastern Missouri in the United States. Two flash flood emergencies were issued, and water rescues and evacuations were prompted, including rescues at a mobile home park in Union City, Tennessee. Downtown Hickman, Kentucky, was impacted by a mudslide which led to a road closure for a road leading to the town.

## Meteorological history

In the early morning hours of August 2, convection developed across northern Missouri in an increased low-level convergence zone, precipitable water values around 2 inches, and a moist, moderately unstable airmass with most-unstable convective available potential energy (CAPE) around 2000 j/kg. The strengthening low-level convergence zone paralleled a west-northwesterly flow aloft, allowing training convection to occur. The convection then merged into a mesoscale convective system several hours later with the convection spreading from southwestern Iowa to southeastern Missouri with abundant moisture and convective instability, along with a strong low-level convergence zone, sustaining the convection, causing heavy rainfall across portions of eastern Missouri and southern Iowa. Shortly thereafter, the mesoscale convective system then expanded into eastern Nebraska, caused by a low level jet, as additional convection developed with a thermodynamic advection occurring. The low level jet then moved to the east and weakened, which caused the convection to dissipate.
Thereafter, on the evening hours, a frontal boundary over central Kansas, along with a humid and moist airmass and instability in southern Missouri, allowed convection to develop and produce heavy rainfall across central Missouri, and west of the Greater St. Louis area as a high risk of excessive rainfall was issued. Training showers and thunderstorms developed across portions of southeastern Missouri and southern Illinois along an elevated convergence axis zone as it moved southeastward towards southwestern Indiana and western Kentucky.
On August 3, mesoscale convective vortex was present along the training convection which caused flash flooding across southeastern Missouri, southern Illinois, western Kentucky, and northwestern Tennessee as the mesovortex moved southeastward. Areas along an isentropic lift above a surface front received heavy rainfall across western Kentucky, southern Illinois, and southeastern Missouri, and high precipitable water values from 2 to 2.4 inches and convective instability between 1000 and 2000 j/kg also supported heavy rainfall. Late in the morning, a second mesoscale convective system moved through areas that had already received flash flooding, causing additional heavy rainfall as the MCS weakened and moved southeastward. Additional factors, including a convergence boundary, precipitable water values around 1.8 inches, and moisture/convective instability all contributed to rainfall rates around 2 inches (51 mm) per hour and causing flash flooding.
In the early morning hours of August 4, additional showers and thunderstorms developed in a corridor extending from central Missouri to northern Alabama due to an increased convective instability, a surface stationary front located over Memphis, Tennessee, and a deep-layer mean flow which resulted in repeating rounds of thunderstorms that moved southeastward over the same areas which had already received heavy rainfall. The convective activity led to flash flooding across Union City, Tennessee, and soon moved into portions of northern Alabama, causing flooding across roadways in the state and in Oneonta, Alabama.

## Impact

Water rescues and evacuations occurred at a mobile home park in Union City, Tennessee, where more than two dozen people were rescued, including by boat. Union City was also flooded. Search-and-rescue operations were conducted in Obion County, Tennessee. Businesses, including a Lowe's store, were flooded in southwest portions of Union City. Flooding forced Obion County Schools to cancel classes on August 4. The National Weather Service in Memphis, Tennessee called the flooding in Union City and surrounding areas "catastrophic". A portion of Interstate 40 was closed. 11.49 inches (292 mm) of rain fell in Union City, which prompted a flash flood emergency. Firefighters in Rives pumped out floodwaters, and utilized drones to display the flooding situation. Roads in Dyer, Jackson, and Trenton were flooded, and Jackson, Madison, and Gibson counties in Tennessee had roads were flooded as well. Flooding also occurred in Weakley, Crockett, and Greene counties in Tennessee. Memphis was also under a flood advisory. St. Francois State Park was temporarily closed due to flooding.
Flash flood emergencies were issued for Union City, and Hickman, Kentucky. Mudslides also occurred in downtown Hickman, sliding onto roads, which led to closures, including a closure on Kentucky Route 94, a road which led to downtown Hickman. Several evacuations occurred in Fulton County, Kentucky.
Portions of Missouri received heavy rainfall, including Columbia, Missouri, receiving 3.77 inches (96 mm) on August 3, breaking a 113-year record. Portions of Sikeston and Chaffee flooded, with the latter location including nearby a high school. Roads were flooded across numerous counties in Missouri. The Missouri River 340 ended as a result of heavy rain, which caused the river's water level to rise, posing a hazard. Hundreds of power outages occurred across the state. Water rescues and flooded roads also occurred in Kirksville, inundating vehicles and stranding drivers. Gerald received nearly 4 inches (100 mm) in 30 minutes according to the Gerald-Rosebud Fire Protection District, flooding basements and cars and prompting a water rescue. U.S. Route 50 was flooded.
In Alabama, roads, including U.S. Route 231 and Alabama State Route 75, in Oneonta were flooded, forcing emergency management to rescue several people from their cars. Floodwaters also entered businesses in Oneonta.

## Aftermath

The Obion County Emergency Management Agency will partner with an agency in Kentucky to provide temporary housing for flood victims. Shelters were opened in Union City, Tennessee as well. The Tennessee Highway Patrol assisted with the Obion County Sheriff and Union City law enforcement. Flood recovery efforts also started in Sikeston, Missouri. The Salvation Army and a nonprofit organization from western Kentucky responded to the floods, assisting flood victims.