A Rare Tornado Merger Observed in the 24 May 2011 El Reno, Oklahoma, Supercell

Unique observations of the merger of two tornadoes are documented using data from four radars, including one WSR-88D (KTLX), one polarimetric S-band radar (KOUN), and two phased-array radars: the multifunction phased-array radar (MPAR) and the Mobile Weather Radar, 2005 X-band Phased-Array (MWR-05XP). One of the tornadoes involved in the merger was an EF5 tornado and the other likely was a previously undocumented tornado; upon merging both the intensity and size of the resulting tornado increased a great amount. The formation of the second tornado is discussed using data from KTLX and KOUN and the merger process is discussed using the phased-array radar data. MWR-05XP electronic scanning in elevation allows for the merger process to be examined up through storm midlevels every ~10 s using PPIs and 3D isosurfaces of azimuthal wind shear. The similarities between this case and another tornado merger case also are discussed.