Leveraging observations from the Verification and Origins of Rotation in Tornadoes Experiment-Southeast (VORTEX-SE) to investigate the role of boundary layer heterogeneities on convection initiation

The Verification and Origins of Rotation in Tornadoes Experiment-Southeast (VORTEX-SE) is an experiment focused on addressing the unique aspects of severe weather development and evolution over the southeastern US. During the first phase of VORTEX-SE, which was conducted between 1 March and 1 May 2016, a network of surface and ground-based remote sensing instruments were deployed over the VORTEX-SE domain, which encompasses much of northern Alabama. These instruments included Doppler radars (polarimetric X-band and C-band), planetary boundary layer (PBL) profiling instruments (microwave radiometer, atmospheric emitted radiance interferometer [AERI], and Doppler wind lidar), rawinsondes, a small unmanned aerial system (sUAS) outfitted with temperature/humidity sensors and infrared camera for deriving land surface temperatures, a network of surface meteorological stations, and two 10 m flux towers. In the present study, we use measurements from these platforms obtained during two intensive observation periods (IOPs) from the 2016 campaign to investigate the role of PBL heterogeneities on convection initiation (CI). We describe results from IOP 4c (30 April 2016), in which the removal of an elevated capping inversion resulted in region-wide CI and several discrete cells in the VORTEX-SE domain briefly acquiring rotation. We also present findings from IOP 4d (1 May 2016). Hourly rawinsondes released at six locations during this IOP near Decatur, Alabama, coupled with dual-Doppler radar coverage, enable us to investigate the role of PBL heterogeneities on a CI event that occurred at 2055 UTC. Finally, we discuss challenges and lessons learned from these IOPs, as well as other IOPs conducted during the first phase of VORTEX-SE, for studying severe weather development over the southeastern US.