Observed Relationships between the Kinematics and Infrasound Sources within the 19 March Alabama Tornadic Supercell

Previous studies have hypothesized a correlation between tornadoes and infrasound signals, which consist of acoustic frequency ranges less than 20 Hz. This has lead to theories that suggest infrasound may be a potentially viable source of early tornadogenesis direct detection that may have utility in tornado warnings. In order to further explore this hypothesized physical relationship, the UAH-SWIRLL and the National Center for Physical Acoustics (NCPA) collaborated to deploy a network of infrasound sensor arrays within a mesoscale network of radar and profiling instruments during 2018 VORTEX-SE field campaign.

On 19 March 2018, a tornado outbreak affected north central AL and other parts of the Tennessee valley. During this event a supercell that moved over northern AL into the VORTEX-SE mesoscale network produced several tornadoes. One of these tornados was rated as a high-end EF-2 with a path length of ~60 km. This supercell was sampled by the UAH Advanced Radar for Meteorological and Operational Research (ARMOR) C-band polarimetric radar, and the Oklahoma University-Shared Mobile Atmospheric and Teaching Radar (SR3) C-band polarimetric radar during the entire tornadic phase. The supercell also passed in close proximity to three of NCPA infrasound sensor arrays, two atmospheric profiling systems, and one mobile sounding site during the event. A multiple-Doppler radar analysis using the ARMOR and SR3 is utilized to relate storm attributes, including updraft strength, updraft mass flux, vertical vorticity maximum, turbulent kinetic energy estimated from spectrum width, and the polarimetric direct detection signature to the infrasound emissions. In addition, the Earth Networks Total Lightning Network (ENTLN) is used to derive the five-minute mean flash rate and flash size, which is compared to the 2-8 Hz band power and other relevant infrasound signals to identify correlations with other possible sources of infrasound within the storm. Using these analyses, a comparison is made with the data from the NCPA infrasound arrays to infer possible sources of infrasound in the supercell storm before, during, and after the tornadic phase. This is believed to be the most comprehensive data set collected to date that examines the hypothesized infrasound-tornado relationship.