Rapid Intensification Mechanisms Including the Role of Storm Mergers in the 22 May 2011 Joplin, MO Tornadic Storm

The rapid intensification of low-level vertical shear due to mechanisms such as storm mergers can result in local environments more favorable for tornadogenesis than found in the surroundings. Following the work of Lemon 1976 and Lee et al 2006, this study uses high-resolution WRF simulations to analyze the significance of storm mergers in the subsequent intensification of the mesocyclone and tornadic vortex in the 22 May 2011 Joplin, MO case. This case was noted for the rapid evolution of the storm from tornadogenesis to peak intensity, as well as the unusually devastating tornado in an environment not normally associated with it.

In the high CAPE, low shear environment not favorable for the EF-5 tornado that occurred, a local intensification mechanism was necessary. Real-data WRF simulations are used to reproduce behavior observed in the event such as storm mergers and other storm intensification mechanisms. Soundings retrieved from the near-storm environment in those runs are used in idealized simulations to test storm morphology resulting from minor modifications in the shear and thermodynamic profiles. Allowing for tests without the effects of boundaries and storm interactions, the idealized runs help to identify the effects of individual changes in the local storm environment. This work reproduces and identifies modifications in the local environment leading to the rapid intensification of the mesocyclone prior to tornadogenesis.