Complex Supercell Mergers and Storm-Scale Interactions During Recent Significant Severe Weather Outbreaks

During the course of documenting and researching the violent tornadoes from the historic 27-28 April 2011 outbreak, several operational and research meteorologists commented that a single long-track supercell produced four violent tornadoes. The tornadoes that appeared to be produced by this single supercell were the Philadelphia MS EF-5, Cordova AL EF-4, Rainsville AL EF-5, and Ringgold GA EF-4. These claims sparked a more detailed investigation into whether or not a single storm produced four violent tornadoes. Additionally, this investigation led to an examination of complex cell mergers and storm-scale interactions that occurred during the 27 April 2011 and 02 March 2012 outbreaks. Preliminary documentation and analysis of several tornadic storms reveal that the relatively small region impacted by numerous supercells on 27 April 2011 led to several complex mergers / interactions between 1) two individual supercells, 2) independent single cells with supercells, 3) daughter/feeder cells with their parent supercells, and 4) independent wave-like reflectivity segments (WRS) interacting with both convective lines and supercells. Many of these same types of mergers / interactions were observed with tornadic supercells during the 02 March 2012 Outbreak, some of which appear to be destructive with respect to storm structure while others appear to be constructive with tornadogenesis observed briefly after the interactions occurred. A radar analysis of several of these cases, comparisons to cell mergers observed during the 20 May 2013 Moore OK EF-5 tornadic supercell, and a discussion on the operational utility of cell merger / interaction identification will be presented.