The Streamwise Vorticity Current: Its Origin and Strategies For Remote Detection

The Streamwise Vorticity Current (SVC) is a horizontal, helically rotating current of streamwise vorticity located along the forward flank downdraft boundary (FFDB) of a supercell thunderstorm (Orf et al. 2017). It resides on the cool side of the FFDB where it flows rearward and is eventually tilted upward into the updraft. In this presentation, model data fields, both two and three dimensional, will be shown for each term in the vorticity equation in an attempt to better understand the mechanisms that generate the SVC in this 30 meter resolution simulation of the 24 May 2011 El Reno tornadic supercell. The primary interest of the SVC is that it appears to play an important role in intensifying the low-level updraft via non-linear dynamic pressure perturbations. The vorticity associated with the SVC creates a lobe of low pressure that extends horizontally from the main pressure deficit of the updraft. The pressure deficit associated with the SVC intensifies the low-level updraft and likely aids in the tornado-genesis process. While these model simulations are important research, they must be related to observational and operational applications to be useful. It is important to investigate the possibility of detecting the SVC using remote sensing techniques, particularly radar. We will present simulated reflectivity and velocity data from the simulation to demonstrate what the SVC may look like in Range Height Indicator (RHI) and Plan Position Indicator (PPI) scans. Demonstrating what this feature might look like on radar will be useful to future field projects seeking to study the SVC. In our simulations of the 24 May 2011 El Reno storm, the SVC is present several minutes before the tornado. If it can be identified via radar it could lead to longer tornado warning lead times.