Meteorological "Cause" and Characteristics of Widespread Heavy Precipitation Events in the Texas Gulf Basin 2003-18

Texas is one of the most flood-prone states in the United States. Recent events such as Hurricane Harvey have demonstrated the vulnerabilities of the region to intense, widespread, and long-duration precipitation events. The major river basin that encompasses much of northern, central, and eastern Texas is the Texas-Gulf - home to several major population centers, and an abundance of natural and cultural resources. Numerous studies have examined the characteristics of heavy precipitation from local to national scales. The specific meteorological cause of events is often excluded from climatological analyses, although recent research is moving toward this type of framework. “Meteorological cause” refers to the weather type primarily driving an event, including tropical and extratropical cyclones, thunderstorms (convection), weather fronts, and/or combinations of the above.

This work examines the meteorological cause and associated dynamic and thermodynamic characteristics of heavy precipitation in the Texas-Gulf basin 2003-18. A base threshold for heavy precipitation events at each domain grid-point is the 95^th percentile 24hr accumulation (ending 12UTC) using the Stage IV multi-sensor dataset. ‘Widespread Heavy’ events refer to days with heavy rain across large portions of the basin the basin, equivalent to the 90^th percentile or above for basin accumulation and area. Using expert assessment, events are categorized into a meteorological cause using archived weather and radar imagery. Seasonal and inter-annual frequencies of events by cause will be discussed, including event characteristics such as duration and rain-rates, as well as general characteristics of heavy precipitation events over the period of study, and the large-scale conditions and causes that favor particularly widespread extreme events, evaluated from North American Regional Reanalysis (NARR). This work provides a climatological underpinning for analysis of future projections of the region’s extreme precipitation dis-aggregated by meteorological cause. Planned work will be briefly discussed.