An Intercomparison of WSR-88D and ARMOR Radar Observations of the 14 July 2015 Tennessee Valley Tornadic Quasi-Linear Convective System

An anomalous tornadic quasi-linear convective system (QLCS) impacted the Tennessee Valley region of northern Alabama during the late afternoon and early evening hours of 14 July 2015. This event was anomalous from the perspective that tornadoes are typically rare in this region during July. At least 6 tornadoes were documented. All of the tornadoes were EF0 or EF1 intensity on the Enhanced Fujita Scale, but a few of the tornadoes were larger (up to 200 m wide) and longer-lived (at least 37.9 km long). These tornadoes presented a particular challenge to warning operations due to the well-perceived challenges of QLCS tornado detection, including rapid generation and dissipation and shallow circulation depth, in addition to a lack of anticipation of prolific circulation generation as well as the structure of the QLCS and its orientation relative to the local Weather Surveillance Radar-88D (WSR-88D) sites at Hytop, Alabama (KHTX) and Columbus, Mississippi (KGWX).

The University of Alabama in Huntsville's (UAH) Advanced Radar for Meteorological and Operational Research (ARMOR) proved to be a valuable asset in post-storm assessment and surveys, particularly since all recorded tornadoes occurred within 75 km of the ARMOR radar site, located at Huntsville International Airport in Huntsville, Alabama. ARMOR did encounter issues in real-time, however, due to power and/or communications issues caused by the storm. In this presentation, we compare and contrast the ARMOR radar signatures associated with several of the tornadoes from this event with the signatures from the KHTX and KGWX WSR-88D radars. We discuss specific instances of all three radars aiding in post-storm assessment and identification of tornadoes, particularly the ARMOR radar. We conclude by discussing the necessity of additional gap-filling, fixed Doppler radar sites for proper identification and study of the variety of potential physical mechanisms that may produce QLCS tornadoes, particularly in light of the upcoming VORTEX-SE field campaign.