An Idealized Modeling Study of the Nontornadic and Tornadic Supercells Intercepted by VORTEX2 on 10 June 2010

Why do only a relatively small fraction of supercells produce tornadoes? This remains an overarching question in the field of severe storms. Our prior observational study of the 10 June 2010 VORTEX2 case examined a tornadic supercell and a nontornadic supercell evolving in close proximity and suggested that a combination of the following likely led to the differences in tornado production: (1) increasing low-level environmental wind shear that only the tornadic storm lived long enough to experience and (2) a storm merger that led to the early demise of the nontornadic supercell. To further investigate the roles of (1) and (2), we are conducting idealized simulations, based roughly on the observed conditions, using the Bryan Cloud Model 1 (CM1). The same thermodynamic profile is used for both storms, but the wind profiles differ. Preliminary results show that the simulated supercell using the hodograph representing the conditions near the nontornadic storm does not produce robust near-surface vortices, whereas the simulated supercell using the hodograph representing conditions near the tornadic storm does. However, when the low-level shear in the environment of the nontornadic supercell is increased over time, this storm begins generating robust near-surface vortices. This suggests that, had a storm merger not led to its premature demise, the nontornadic supercell likely could have produced a tornado. Additional experiments with modified environmental shear profiles are analyzed to determine how organized (i.e., “healthy”) the nontornadic supercell in this case needs to be such that experiencing increasing low-level shear in its environment notably enhances its potential for tornado production.