The 12 May 2010 tornadic supercell intercepted by VORTEX2 near Clinton, Oklahoma

The pretornadic and tornadogenesis phases of the 12 May 2010 supercell in Clinton, Oklahoma, intercepted by the second Verification of the Origins of Rotation in Tornadoes Experiment (VORTEX2) are analyzed. Radar data from the WSR-88D in Frederick, Oklahoma (KFDR) and from two Doppler-on-Wheels (DOW) radars are combined with mobile mesonet and sounding observations. Low-level rotation intensifies in two separate periods, the second of which precedes tornadogenesis, which occurs around 0138 UTC. During the first period of strong low-level rotation, a descending reflectivity core (DRC) forms and descends to low levels along the axis of maximum rotation. The DRC descent appears to be associated with the dissipation of the initial vortex and the formation and subsequent intensification of a new one. Circulation rapidly increases after the arrival of the DRC at low levels, reaching a maximum value at the time of tornadogenesis.