Analysis of Radar-Estimated Rotation and Divergence Associated with Kinematic Features Observed During RiVorS

Recently, interest has increased in verifying the presence of supercellular “rivers” of locally-enhanced vorticity commonly found in numerically simulated supercells. In simulations, these features tend to emanate from the storm’s main precipitation region, move south and/or westward toward the low-level updraft, and are thought to be associated with surface pressure deficits and cyclonic wind shifts. The Rivers of Vorticity in Supercells (RiVorS) field project of 2017 was among the first attempts to directly observe these features. A diverse dataset containing mobile mesonet and mobile Doppler radar measurements from both tornadic and non-tornadic storms was collected.

Preliminary analysis of observed kinematic fields from RiVorS reveals the presence of a number of pronounced, small-scale convergence signatures with varying thermodynamic characteristics. This work utilizes linear, least-squares derivative (LLSD) analysis to produce rotational and divergent shear fields for available WSR-88D and mobile radar data collected during the project. These fields are used to examine storm structure in the low and near-ground levels and attempt to infer processes that may yield notable near-surface kinematic features encountered during RiVorS deployments. Quality-controlled mobile mesonet measurements are matched in space and time to radar-derived fields to explore the evolution of these features and their parent storms. Finally, observed characteristics of RiVorS storms are compared to those of other well-sampled supercells and evaluated within the context of existing conceptual models with a focus on the development of significant low-level rotation.