Collaborative Research: Improving Our Understanding of Supercells from Convection Initiation to Tornadogenesis via Innovative Observations, Simulations, and Analysis Techniques

Decades of study of supercell thunderstorms and tornadoes have resulted in better forecasts, better warnings, and increased public safety. However, despite this progress, there are still fundamental questions about tornado formation and the initiation of storms in environments that are conducive for tornadoes. This project will use new observations and new analysis techniques to uncover answers about the origin of tornado rotation and whether surface friction is an important factor, and how wind changes with altitude affect the initial development of thunderstorms. The results of the research may provide forecasters with more clues to why some storms form tornadoes while others do not within the same environment. The researchers also plan to contribute to public understanding of science through various outreach mechanisms, and will train multiple graduate students.

This project focuses on a range of questions related to supercell thunderstorms, from initiation to tornado formation. The tornado-related research is guided by three core questions: 1) How important is baroclinically generated vorticity to the development of tornadoes, 2) Is the underlying surface a critical vorticity source for tornadoes, and 3) Why do supercell storms in similar environments often behave so differently? To address these questions, the research team will interrogate a number of well-observed tornadic storms from the VORTEX-II and TORUS field campaigns. Diabatic Lagrangian analysis (DLA) techniques will be conducted on multi-Doppler radar data and combined with swarm-sonde thermodynamic observations to create 4D thermodynamic and velocity fields, which will then be used in material circuit analyses to demonstrate the baroclinic origins of low-level circulation. Additionally, the material circuit analyses will be used on an existing 25-member ensemble of 75-m resolution numerical model simulations. New simulations will be conducted with a more generalized non-equilibrium lower boundary condition, using the two-layer model concept from the engineering community to address the frictional component of the project. New modeling simulations will also be conducted to address uncertainties related to convective initiation in shear and environmental controls on convective modes. The research team plans to target the following questions for the convective initiation (CI) work: 1) What are the variety of ways that vertical wind shear inhibits or facilitates CI, 2) How does their relative importance depend on the altitude and depth of the shear, and on the characteristics of the airmass boundary involved in CI, and 3) To what extent do the characteristics of an airmass boundary, such as its horizontal temperature gradient, depth, and forward speed relative to the environmental winds above the boundary, influence the organization of convective storms?

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.