The Sensitivity of Severe Convective Storm Mode to Updraft Initiation Morphology Across Large-scale Environments

Severe convective storm modes (SCSMs) are responsible for the majority of severe hazards such as tornadoes, hail, and damaging straight-line winds. This work aims to distinguish the role that the initial morphology of updrafts may play in determining SCSM and investigate sensitivities across various large-scale environments (LSEs). Supercells, quasi-linear convective systems (QLCSs), and mixed modes (supercells and QLCSs occurring concurrently in the same region), are examined using idealized simulations in Cloud Model 1. With 250-m grid spacing, ensembles are developed that use different initial updraft patterns that represent real-world setups (e.g. isolated updrafts, scattered clusters of updrafts, broken linear updrafts, and hybrid (broken linear updrafts with scattered clustered updrafts to the east)). LSEs representative of each storm mode are found using the Smith et al. (2012) severe convective mode database that cover a range of convective available potential energy and deep-layer shear regimes. Updraft initiation is accomplished through multiple ellipsoidal regions of upward acceleration centered at 1.5 km above the lowest model level with vertical radii of 1.5 km. The horizontal shape, location, maximum magnitudes in upward acceleration, and both the start time and duration of the forcing regions are randomly varied to mimic real world variability in convective initiation. Preliminary results indicate that the dominant SCSM is not considerably sensitive to initial updraft morphology; however, sensitivities occur with storm longevity and intensity likely due to the nature of cell interactions. These sensitivities will be further explored through additional experiments that modify the magnitude of the deep-layer shear.