11B.3
Comparison of the Tornadic and Nontornadic Supercells Intercepted by VORTEX2 on 10 June 2010

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Wednesday, 5 November 2014: 2:00 PM
University (Madison Concourse Hotel)
Alicia Klees, Pennsylvania State University, University Park, PA; and Y. Richardson and P. Markowski
Manuscript (4.6 MB)

On the evening of 10 June 2010, VORTEX2 collected a rare set of observations of a nontornadic (2345-0040 UTC) and tornadic supercell (0100-0230 UTC) evolving in close proximity to each other in northeastern Colorado. To analyze these supercells, we use single and dual-Doppler radar, mobile mesonet, StickNet, and mobile sounding data. We strive to understand why one supercell produced no tornadoes and the other, at least two, by comparing the storms' environments, outflow temperatures, storm kinematics, and interactions with other convection. Additionally, for the tornadic supercell, we study the evolution of the two tornadoes and the following periods of cyclic mesocyclogenesis.

The storms developed in environments with a low likelihood of significant tornadoes but within climatology for weak tornadoes. The only environmental parameter showing a significant difference between the two storm environments was low-level storm-relative helicity, which was larger in the environment of the tornadic supercell and may have made tornadogenesis more favorable. Virtual potential temperature deficits in the outflow were qualitatively similar for the two storms, both within the normal range for a weakly tornadic supercell. After a few hours, new convection developed along the outflow between the two storms. The nontornadic supercell experienced a merger with one of these new cells, and this merger led to the supercell's demise. Had the merger not occurred, the nontornadic supercell might have had the opportunity to produce a tornado, given the similarities in environment and outflow characteristics to the tornadic supercell. Outflow from the new convection impinged on the northern flank of the tornadic storm and may have made tornadogenesis more likely by enhancing convergence or baroclinity in this storm. In the future, we plan on further evaluating the impacts of the merger on both supercells through model simulations using EnKF data assimilation techniques.

Additional analyses of the tornadic supercell found that the same mesocyclone produced both tornadoes, rather than cycling prior to the production of the second tornado. The subsequent cyclic mesocyclogenesis stages involved multiple cyclonic circulations that evolved in the rear flank of the storm and moved rearward aloft due to strong storm-relative winds. Meanwhile, a strong, deep, and relatively steady anticyclonic vortex also was apparent in the rear flank.