Radar Characteristics of Convective Downdrafts and Environments Observed during the VORTEX-Southeast Project

Storm-generated downdrafts play a significant role in storm evolution, intensity, and duration. Importantly, the properties of forward-flank and rear-flank downdrafts in supercell storms, and descending rear inflow jets in quasi-linear convective systems (QLCS), have been linked to the occurrence of tornadoes. The VORTEX-Southeast project aimed to observe severe convection in northern Alabama during the early spring of 2016 and 2017 to determine the topographic and environmental influences on tornadoes in the southeastern U.S. Since both supercell and QLCS storm morphologies are associated with tornado production in this region of the country, a better understanding of how downdraft and outflow properties of these storms, including radar and environmental pre-cursors, can be used to predict tornadogenesis and other severe weather is needed.

This work utilizes dual-pol and multiple-Doppler radar data collected by five mobile and fixed radars, several sounding and profiler facilities, and surface in situ observations collected during the VORTEX-Southeast project to characterize storm-scale downdraft processes, and environmental and terrain influences upon them. This presentation will discuss preliminary synthesized multi-Doppler wind retrievals and dual-pol radar observations of the observed convective downdrafts to relate their four-dimensional kinematic and hydrometeor properties to in situ surface observations of the low-level outflow and frequent sonde observations of the mesoscale environment. Comparisons of interacting environmental and storm-scale processes occurring in the southeast U.S. with those observed in the central plains will offer improved understanding of regional severe weather and tornado risks. Of particular interest to this research is understanding how dual-Doppler- and dual-pol-observed downdraft properties, including downdraft surges, evolve relative to mesoscale environmental thermodynamic and shear heterogeneity, including stability differences in nighttime vs. daytime events and low-CAPE high-shear conditions that often occur in the southeast U.S.