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Interactions Between a Thermal Boundary and Deep Convection During the 27 April 2011 Superoutbreak
Numerous storms formed on or near this thermal boundary including the Cullman EF-4, Rainesville EF-5, Jackson County EF-4, Smithville EF-5 and, Hackleburg EF-5. All of these storms were measured by one or more of the above radars. Using these radar data, time vs height measurements of maximum Z and rotational velocity can be related to each storm's distance from the boundary. Both the Cullman and Hackleburg storms crossed from the warm side of the boundary to the cool side of the boundary during their lifetimes. A significant change in the LCLs of these can be observed by surface measurements and photography. The EF-5 Hackleburg supercell appears to be the most significantly influenced by this boundary. This storm formed in eastern Mississippi and traversed north Alabama before dissipating in south central Tennessee. It produced a tornado that remained on the ground for approximately 212 km. Surface data indicate that this storm formed just south of the boundary. The storm's first damage report is colocated near the location the storm appeared to have crossed over to the cool side of the boundary. In addition, single and dual-doppler analyses from MAX, ARMOR, and KHTX are used to relate storm structure and strength with proximity to the boundary. Finally, VAD analyses from each radar demonstrates the additional backing of the wind at the surface on the cool side of the boundary. This backing of the surface wind led to an increase of SRH by as much as 400 m2/s2 at the surface on the cool side of the boundary.