Evaluating the Impact of a Scale-aware Three-dimensional Turbulent Kinetic Energy Scheme on Tropical Cyclone Forecasts in the Hurricane Analysis and Forecasting System Tropical Cyclone Research and Review

A Scale-Aware Three-Dimensional Turbulent Kinetic Energy scheme (SA3DTKE) was developed 1) to incorporate three-dimensional shear, transport, and pressure diffusion in predicting turbulent kinetic energy (TKE) and 2) to homogenize the turbulent transport calculation used in large-eddy simulations with one-dimensional planetary boundary layer schemes used in large-/meso-scale models accounting for eddies across scales from small isotropic to large anisotropic turbulence. This study examines the impacts of the SA3DTKE scheme implemented in the Hurricane Analysis and Forecasting System (HAFS) model on tropical cyclone (TC) forecasts by analyzing HAFS simulations of hurricanes Kirk (2024) and Leslie (2024). Results show that SA3DTKE reduces the forecasting bias of track and intensity. SA3DTKE modulates the eyewall and rainband convection and thereby affects TC track via horizontal and vertical advection of wavenumber-1 potential vorticity asymmetries. SA3DTKE reduces the negative intensity bias through enhancing eddy diffusivity and TKE in the lower troposphere, leading to enhanced surface latent heating to maintain a stronger warm core structure. At the same time, stronger frictional force also generated stronger agradient forcing to facilitate the inward transport of absolute vorticity creating a stronger tropical cyclone denoted by the enhanced tangential wind and reflectivity. Grant no. NA22OAR4590523 Grant no. NA22OAR4590177 Grant no. NA22OAR4590178