Continued Analysis of Convective System Evolution Using Convection-permitting Grid Spacing Weather Research and Forecasting (WRF) Simulations

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This research team will investigate the predictability and upscale evolution of mesoscale convective systems (MCSs) and explore techniques designed to improve quantitative and probabilistic precipitation forecasts of these systems, which serve as a pivotal source of both beneficial and sometimes damaging warm-season rainfall over much of the central U.S. and its associated agricultural belt. Research will focus on numerical model simulations employing fine-mesh "convection-allowing" grid spacings (CAGS) of 2-4 km which explicitly represent thunderstorm-scale circulations and related precipitation processes. Two main research thrusts are planned. The first will emphasize understanding the errors present in simulations from the Weather Research and Forecasting (WRF) model of the nocturnal low-level jet (LLJ), planetary boundary layer (PBL) evolution, and stratiform rain region development and how these features impact simulated MCS evolution. The second thrust will involve evaluations of basic issues related to low-level jet intensity and the role they play in the growth of MCSs. An extensive archive of in-house WRF simulations, output from simulations run by outside collaborators, and data from various observational sources would be incorporated, with intellectual merit centered on advancement of the understanding of (1) relationship of LLJ simulation accuracy to prediction of MCSs; (2) impacts of cloud-solar radiation deficiencies within the PBL on MCS simulations; (3) the role of cloud microphysics and near-storm winds on prediction of MCS evolution; and (4) evaluation of neighborhood methodologies applied to ensemble output to improve convective rainfall prediction.Broader impacts of this research will come through expected improvements in forecasts of warm-season convection, which bring considerable societal benefit due to the disruptive nature of severe weather and flooding events. The researchers plan to work closely with NOAA/National Weather Service personnel to increase the research to operations aspect of the work. Education would also be emphasized, with multiple students involved in the research.