SCIPP investigators Dr. Vincent Brown, Derek Thompson, Anna Sitzman, and Dr. Barry Keim recently published an article titled “Rainfall analysis of the May 2021 southeastern Texas and southern Louisiana flood” in Physical Geography. The paper discusses the synoptic setting of the historic rainfall event, which produced 15-19.8 inches of rain across eastern Texas and southern Louisiana. For many affected locations, most of the storm total occurred in just 6-12 hours, causing extensive flooding and leading to over $1 billion in damage. The research also compared the May 2021 event to another extreme precipitation event that affected southern Louisiana, the August 2016 flood.
The extreme rainfall totals observed during the May 2021 event resulted from two slow-moving mesoscale convective vortices (MCV), which arose from thunderstorms that began in western Texas and eastern New Mexico on May 15th. Once the MCVs entered eastern Texas and southern Louisiana, the storms used elevated atmospheric water vapor sourced from a warmer-than-normal Gulf of Mexico to concentrate precipitation across the region. An analysis of the average return interval (ARI) of observed precipitation showed the unique spatiotemporal extent of the storms, with some locations experiencing 6-h rainfall totals that exceeded 200-816-year rainfall events. A Depth Area Duration (DAD) analysis was used to compare the May 2021 event to the August 2016 event. Results showed that precipitation depths for smaller areas and time intervals were higher for the May 2021 event, while the August 2016 event produced more precipitation at larger spatiotemporal scales. These differences were attributed to differing precipitation efficiency processes between the events, with the August 2016 event being more tropical and the May 2021 event more convective.
The paper also highlights the need for further research on extreme precipitation events using DAD, especially with the potential for such events to become more frequent in the future.
For more, read the full paper here.