Analyzing the Role of a Long-Lived Mesoscale Convective Vortex in Mesoscale Ensemble Analyses of the 24 August 2016 Indiana-Ohio-Ontatio Tornado Outbreak

On August 24th, 2016, twenty one tornadoes touched down across Indiana and Ohio. Two of the tornadoes were EF-3 strength, with one tornado in Kokomo, IN injuring 20 people (Guyer et al. 2016) This unusual summer outbreak was not well anticipated in SPC outlooks and other forecasts leading up to the event (Guyer et al. 2016). A convective complex that developed over Iowa the night before the outbreak produced a long-lived mesoscale convective vortex (MCV) that may have played a key role in the development of tornadic storms ahead of it as it moved eastward across northern Illinois and Indiana during the day on the 24th.

In this study we analyze output from a mesoscale ensemble cycled analysis using the WRF model coupled to the Data Assimilation and Research Testbed (DART) Ensemble Kalman Filter (EnKF) system. We focus on the role of the MCV by examining the evolution of the mesoscale environment and severe convective indices in the context of well-known conceptual models of MCVs embedded in environmental shear.