My Master's research focused on the tornado outbreak of 24 August 2016 in Indiana and Ohio. We used the WRF Model to simulate this event and manipulated the output so that it was compatible with pressure decomposition code so that we could analyze pressure perturbations within the simulated storms of interest. Findings stress the importance of ingesting strongly sheared air near the surface for the formation of supercells during this event. A differential heating boundary owing to anvil cover seems to have played a crucial role in preserving the horizontal vorticity owing to the shear near the surface (Gray and Frame 2019).

I switched gears for my PhD research, simulating idealized supercells using CM1. We explored how the orientation of the 3–6-km vertical wind shear vector impacts the longevity of and thus the potential for near-surface vortex formation within simulated supercell thunderstorms. Our investigation is significant because these impacts have been relatively unexplored and because the midlevel winds dictate where outflow surges develop within supercells. We found that the storm-relative location of outflow surges can affect the magnitude of the convergence beneath an updraft, the buoyancy of the air flowing into an updraft, and the potential tilting and undercutting of an updraft by outflow, all of which can influence supercell longevity and thus the potential for near-surface vortex formation (Gray and Frame 2021).

We then looked into streamwise vorticity currents (SVCs) produced by the outflow of simulated storms (Gray and Frame 2023). We found that SVCs do not significantly differ between the different storms and that SVCs that precede tornado-like vortices do not differ significantly from SVCs that do not precede tornado-like vortices. Using trajectories, we identified two different airstreams that contribute to SVCs: one that flows along the length of the SVC, and another that merges with the SVC from the modified inflow. Vorticity budgets reveal that stretching of horizontal vorticity is the greatest contributor to the streamwise vorticity that develops in the SVC. In this study, we conclude that it is plausible that an SVC can drastically enhance a low-level mesocyclone, increasing the chance for tornadogenesis. When a semi-slip lower boundary is introduced to the model (Gray 2023), low-level updrafts become weaker, but more steady compared to simulations with a freeslip lower boundary. Forward-flank convergence boundaries also become more common with a semi-slip lower boundary. Environmental streamwise vorticity plays a greater role in SVCs developing along a forward-flank convergence boundary and baroclinically-generated streamwise vorticity plays a greater role in SVCs along a left-flank convergence boundary. Streamwise vorticity values in SVCs simulated with a freeslip lower boundary are likely too large, suggesting that output from freeslip simulations be interpreted with caution.

Ongoing research includes investigating extreme precipitation events in a future climate. Using WRF, we are developing an ensemble of simulations for several extreme rainfall events. Then a pseudo global warming approach will be used to simulate these extreme rainfall events in the future. Output from our ensemble will be used to force a hydrology model to investigate the uncertainty of flooding potential in the future.