Examining the sensitivities of high-shear, low-CAPE convection on low-level hodograph shape

Severe convection occurring within high-shear, low-CAPE (HSLC) environments is a considerable forecasting concern due to associated high false alarm rates and low probabilities of detection for operational products, including tornado watches and warnings. One reason for this poor skill is our overall limited understanding of the dynamics associated with HSLC convection and how it produces severe hazards despite limited buoyancy. Idealized simulations meant to explore HSLC convection have largely been limited to mini-supercell simulations utilizing soundings based upon tropical HSLC environments and suffer from fairly low resolution. Given that many extratropical HSLC events occur in association with quasi-linear convective systems (QLCSs), and because of the small spatial scales of accompanying centers of rotation (i.e., on the order of 2-4 km in vertical and horizontal extent), high-resolution studies of HSLC QLCSs are required to answer several remaining questions involving HSLC severe convection.

Recent research has identified low-level wind shear vector magnitude as a primary discriminator between HSLC environments associated with convection capable of producing severe hazards and that associated with non-severe convection. Therefore, herein, we will explore the sensitivities of idealized HSLC convection to low-level shear vector magnitude and hodograph shape. In particular, we seek to evaluate the role of forcing-relative bulk wind difference components and storm-relative helicity in the lowest 1-3 km on the production of low-level updrafts, mesocyclones, mesovortices, near-surface vortices, and near-surface wind speed maxima. This will be the first in a series of studies attempting to isolate the relative impacts of environmental constituents on the intensity of high-resolution, idealized HSLC convection.