Exploring Tornado Maintenance with Observations and Idealized Simulations

In this study, we combine observations of ongoing tornadoes together with idealized simulations to better understand the mechanisms controlling tornado maintenance. This study builds on Marquis et al. (2012) by comparing the evolution of the surrounding airflow for observed short-lived tornado cases compared to longer-lived cases, using single- and dual-Doppler wind fields from VORTEX2 and prior experiments, as well as thermodynamic fields when available. Key differences are then modeled in an idealized manner to clarify the dynamical processes. The goal of the numerical simulations is not to study vortex formation; rather, our goal is to obtain an idealized tornado-strength vortex and investigate its maintenance by trying to disrupt the vortex via mechanisms culled from the observations. For example, a cooling rate may be applied to the air at the lower boundary, or a mean wind may be applied across the domain. These two example controls are motivated by the hypotheses that tornado maintenance depends on the buoyancy or potential buoyancy of the air ingested by the tornado, and/or the extent to which the tornado can remain “connected” to the midlevel updraft.