Dylan R. Card, Kristen L. Corbosiero, Brian H. Tang, Robert G. Fovell, and Ryan D. Torn
Tropical cyclones (TCs) pose a significant threat to life and property, and exhibit many severe weather hazards as they make landfall, such as storm surge, strong winds, flooding rains, and tornadoes. TC convection is associated with nearly all of these hazards, which can extend hundreds of kilometers inland. Thus, understanding the characteristics and organization of convective cells is important to mitigating risk. Observational studies have noted that TC convection tends to organize downshear and that rotating thunderstorms tend to occur in the downshear-right quadrant of the TC. Rotating thunderstorms in TCs are strongly influenced by the low-level helicity and convective available potential energy (CAPE), which have been highlighted in numerous modeling studies. The distribution and magnitude of low-level helicity and CAPE can be strongly influenced by microphysics and planetary boundary layer parameterizations in numerical weather prediction. Modeling studies have also shown that convective cells tend to form upshear right and mature as the traverse cyclonically around the TC.
High-resolution Weather Research and Forecasting (WRF) simulations of hurricanes Harvey and Irma (2017) will investigate the role of microphysics and boundary layer parameterizations in determining the structure and distribution of rotating and non-rotating convection in TCs. Specifically, this project will examine how double- and single-moment microphysics parameterizations as well as local, non-local, and hybrid planetary boundary layer parameterizations impact the distribution, structure, and longevity of convection. The high resolution (1 km) of these simulations will also allow for the investigation of whether boundaries at the TC or sub-TC scale influence convective organization. This study is unique in that it plans to investigate the interactions between microphysics and planetary boundary layer parameterizations on the development, evolution, and structure of both tropical cyclone convection and boundaries during landfall.
