Investigating the Upstream and Downstream Effects of the SVC

High-resolution computer simulations of severe storms can provide a high-fidelity 4D picture of storm processes unable to be examined from observations alone. One such recent high-resolution simulation of a supercell revealed a coherent storm-scale feature called the streamwise vorticity current (SVC), that was unable to be fully resolved in previous simulations or observations of supercells. Since its ``discovery" in 2017, it has been confirmed to exist in both real supercells via radar observations as well as other computer simulations. Some of the latter simulations have theorized that the SVC augments or may even become the low-level mesocyclone as the horizontal streamwise vorticity becomes reoriented into the vertical in the lowest kilometer underneath the updraft; however, others have argued that baroclinic vorticity generation plays a minor role in contributing to the low-level mesocyclone. Given that our current understanding of tornadogenesis relies on vertical accelerations from the low-level mesocyclone, it is important to understand what may modulate the low-level mesocyclone strength. Furthermore, from an operational standpoint, it is desirable to understand any environmental conditions that may support SVC development to add to the tornado forecasting toolkit. Cloud-model 1 simulations exploring a particular phase space of vertical wind shear profiles are used to investigate supercell evolution and SVC existence. Specifically, three magnitudes of three free parameters create a 27 simulation phase space “cube”. The three free parameters varied consist of 0-1 km AGL shear, storm-relative inflow (0-1 km AGL), and the inflow/outflow angle, an angle defined between the 0-1 km AGL mean storm-relative wind vector, and the 9-11 km AGL mean storm-relative wind vector. Unfortunately, five of the 27 simulations consisting of weak storm-relative inflow and weak low-level shear failed to initiate an organized supercell, so only 22 of the simulations are used to interrogate the phase space between one to four hours of simulation time. It is established and verified herein that the storm-relative inflow primarily modulates supercell attributes such as the updraft width, updraft mass flux, precipitation footprint, minimum cold pool temperature, and inflow low strength. Also previously established and verified is the relationship between the inflow/outflow angle and downburst location, minimum cold pool temperature, updraft/downdraft angle, the inflow low orientation, and storm-scale boundary orientations (including the SVC). The inflow/outflow angle was found to not be the best metric for measuring the orientation of the storm-scale boundaries, so new formulations are proposed. Strong low-level shear was also found to primarily drive mesocyclone strength, influenced the inflow low strength, influenced the minimum cold pool temperature and placement, and changed the storm-scale boundary orientations. Finally, while the SVC magnitude was driven by the low-level shear magnitude, the likelihood of the SVC was highest for strong storm-relative inflow, small inflow/outflow angles, and moderate low-level shear. While no clear relationships between SVCs and tornado-like vortices (TLV) were found in the simulation suite, 60\% of TLVs overlapped with SVCs in the moderate low-level shear experiments, meaning that SVCs may act as a tipping point for tornadoes in marginally favorable tornadic environments. Classifying TLV-genesis mechanisms, two SVC TLV-genesis mechanisms were identified and accounted for the majority of TLV-geneses in simulations with SVCs. TLVs either formed underneath the upward-tilting SVC or along the leading edge in conjunction with the rear-flank gust front. The former was in close proximity to a local maximum in vertical accelerations induced by the SVC. Finally, parcel analysis revealed that the SVC parcels primarily fed the northern comma-head portion of the low-level updraft, and overwhelmingly contributed to the region of fastest vertical velocities in the low-level updraft.