The hypothesis motivating the current study is that changes to the orientation and magnitude of the low-level shear vector may alter the structure and motion of supercell outflow, such that the position of the near-ground circulation relative the overlying mesocyclone may be modulated by shear, regardless of effects on the vertical perturbation pressure gradient. Results from preliminary numerical simulations in which the low-level shear is varied with minimal changes to near-ground storm-relative helicity (and minimal effect on mesocyclone strength aloft) will be presented.
Furthermore, the strength and orientation of the low-level shear in the vicinity of supercell gust fronts may also be significantly altered by the storm itself, through horizontal accelerations in proximity to the updraft or reductions in vertical mixing beneath the storm anvil. Consequently, measures of low-level shear provided by proximity soundings may not adequately reflect local shear conditions encountered by supercell gust fronts. These effects (as depicted by simulations) and their potential ramifications for tornadogenesis will be discussed.