Short-term Forecasts of Left-Moving Supercells from an Experimental Warn-on-Forecast System

Abstract

Most research in storm-scale numerical weather prediction has been focused on right-moving supercells as they typically lend themselves to all forms of high-impact weather, including tornadoes. As the dynamics behind splitting updrafts and storm motion have become better understood, differentiating between atmospheric conditions that encourage right-and left-moving supercells has become the subject of increasing study because of its implication for these weather forecasts. Despite still often producing large hail and damaging winds, leftmoving (anticyclonically rotating in the Northern Hemisphere) supercells have received much less attention.During the 2016, NOAA Hazardous Weather Testbed, the NSSL Experimental Warn-on-Forecast System for ensembles (NEWS-e) was run in real-time. One event in particular occurred on 8 May 2016 during which multiple left-and right-moving supercells developed in western Oklahoma and Kansas-producing many severe weather reports. The goal of this study was to analyze the near storm environment created by NEWS-e using wind shear and other severe weather parameters. Then, we sought to determine the ability of the NEWS-e system to forecast storm splits and the persistence of left-and right-moving supercells through qualitatively analyzing tracks of forecast updraft helicity. Initial results show that the NEWS-e system analyzed several areas favorable for left-and right-moving supercells during which the system forecasted storm splitting and the persistence of both storm types. In particular, hail-producing left-moving supercells were accurately forecast in central and northern Oklahoma while a tornado-producing right-moving supercell was forecast in southern Oklahoma. ABSTRACT (Manuscript