Numerical Simulation of the 24 April, 2002 storm merger between a left moving storm and supercell

During the last fifteen years, the observations and documentation of an isolated storm – supercell merger leading to tornadogenesis in the literature has been quite limited. There still remain many unknowns concerning the processes involved leading to tornadogenesis during the merger. On 24 April 2002, WSR-88D observations from WFO St. Louis (KLSX) indicated that an isolated left-moving storm from an earlier storm split appeared to merge along the western flank of a hybrid supercellular storm over south-central Missouri. Just after the merger, a tornado occurred and caused a 9 mile continuous track of F0 - F2 damage over southeast Madison County Missouri.

This study will focus upon analysis of high-resolution simulations of supercell-split cell merging within the environment found on this day. Utilizing sounding conditions near the time and location of the 2002 event, we will carry out idealized simulations with the Weather Research and Forecasting (WRF) model. The modeling methodology and our analysis will address broken line orientation versus the ambient cloud-bearing vertical shear, timing and location of cell development (and splitting) along the line, cell merging scenarios, and the resulting merged cell characteristics.