Horizontal Vortex Tubes near a Simulated Tornado: Three-Dimensional Structure and Kinematics Atmosphere

Supercell thunderstorms can produce a wide spectrum of vortical structures, ranging from midlevel mesocyclones to small-scale suction vortices within tornadoes. A less documented class of vortices are horizontally-oriented vortex tubes near and/or wrapping about tornadoes, that are observed either visually or in high-resolution Doppler radar data. In this study, an idealized numerical simulation of a tornadic supercell at 100 m grid spacing is used to analyze the three-dimensional (3D) structure and kinematics of horizontal vortices (HVs) that interact with a simulated tornado. Visualizations based on direct volume rendering aided by visual observations of HVs in a real tornado reveal the existence of a complex distribution of 3D vortex tubes surrounding the tornadic flow throughout the simulation. A distinct class of HVs originates in two key regions at the surface: around the base of the tornado and in the rear-flank downdraft (RFD) outflow and are believed to have been generated via surface friction in regions of strong horizontal near-surface wind. HVs around the tornado are produced in the tornado outer circulation and rise abruptly in its periphery, assuming a variety of complex shapes, while HVs to the south-southeast of the tornado, within the RFD outflow, ascend gradually in the updraft. 2019 Grant no. NA17OAR4590188 OAR (Oceanic and Atmospheric Research) WPO (Weather Program Office) NSSL (National Severe Storms Laboratory) NWS (National Weather Service) SPC (Storm Prediction Center) CIMMS (Cooperative Institute for Mesoscale Meteorological Studies) Submitted https://doi.org/10.3390/atmos10110716 CC BY 1948