Evaluation of the MYNN Planetary Boundary Layer Scheme in the Hurricane Weather Research and Forecast System (HWRF)

Numerical simulations of tropical cyclones are known to be sensitive to the parameterization of the planetary boundary layer (PBL), especially to the vertical profile of eddy diffusivity, which impacts the strength and depth of the radial inflow into the storm. The Hurricane Weather Research and Forecast system (HWRF) is one of NOAA’s operational hurricane models and currently uses the Global Forecast System (GFS) Eddy Diffusivity-Mass Flux (EDMF) PBL scheme. The impact of replacing this scheme with the Mellor–Yamada–Nakanishi–Niino (MYNN) PBL scheme is tested in this work. Comparisons between the tropical cyclone track, intensity, and wind radii forecasts produced by the two different HWRF configurations for select 2016–2018 North Atlantic tropical cyclones will be shown. In addition, the boundary layer structure in the two sets of model simulations will be compared to observations collected by dropsondes deployed by hurricane reconnaissance aircraft. The feasibility of implementing the MYNN PBL scheme in the operational HWRF will also be discussed from a perspective of computational efficiency and forecast model performance.