RAL SEMINAR: Using Observations from TORUS to Better Understand and Simulate the Evolution of Two Proximate Supercells on 8 June 2019

The Targeted Observation by Radars and UAS of Supercells (TORUS) field campaign

collected observations of two supercells in eastern CO and NW KS on 8 June 2019. These storms occurred in close spatial and temporal proximity; however, their structure and hazard production differed markedly. The first storm produced no mesocyclonic tornadoes, struggled to maintain itself after crossing out of Colorado, and dissipated near Goodland, KS after 2200 UTC.

The second supercell developed just after 2230 UTC and nearly tracked over the same location where the first storm dissipated as it rapidly intensified, turned sharply rightward, and went on to produce several mesocyclonic tornadoes after 0100 UTC. This presentation discussed analysis which used data collected by TORUS to examine the following questions: 1) Why was the second storm able to become cyclically tornadic where the first storm struggled to survive? and 2) How does assimilating different subsets of the data collected by TORUS affect storm-scale ensemble forecasts of both supercells? Using observations from TORUS to examine the first question, we found that rapid changes in the low-level wind profile, interactions with two mesoscale boundaries, the second storm’s merger with a new updraft which formed just to its west, and the influence of a strong Rear Flank Internal Surge (RFIS) likely account for much of storm 2’s greater intensity and longevity. To answer the second question, we conducted data

denial experiments assimilating several subsets of observations from TORUS and found notable impacts on analyses and forecasts of these storms’ evolution.