On 22 May 1995, during VORTEX, the following unusual sub-storm scale features were documented in pseudo-dual Doppler analyses of ELDORA data of a nontornadic supercell hailstorm: an intense, elevated vortex couplet with an associated localized jet and a deep convergence zone at the interface between the jet and strong southeasterly inflow (Bluestein and Gaddy 2001, MWR, 2270-2289). Unfortunately, the temporal continuity of the dataset was not good and there were great uncertainties in terminal fall velocities, owing to the large hail that fell. Consequently, no further diagnostic studies were possible.

The purpose of this presentation is to describe the dynamics of the jet and cyclone-anticyclone couplet through numerical simulation experiments. Using proximity mobile soundings released by VORTEX crews, we were able to simulate a convective storm that developed a cyclone-anticyclone couplet and jet similar to the one observed in the VORTEX storm. We used the Klemp-Wilhelmson model at 500 m resolution in the horizontal, initialized by a warm bubble. The simulated storm developed the features of interest after a few hours. In the model simulations, the development of the jet and cyclone-anticyclone couplet was periodic, with a period on the order of 25 minutes. Vorticity production in the cyclone and anticyclone was computed from terms in the vorticity equation calculated in a Lagrangian framework for air parcels that ended up at the centers of the cyclone and anticyclone at the time of their greatest intensity. The results will be discussed, along with a brief discussion of how we propose to determine the range of conditions under which such features can appear in supercells.