Tropical cyclone track forecasting with the analytic beta gyre and bogus vortex

The wind of beta gyre are constructed by the analytic function based on the dynamics of asymmetric tropical cyclones and added to the idealized 3-dimensional axisymmetric bogus vortex. The bogus vortex are merged in the global analysis (bogussing) and WRF (Weather Research and Forecasting) model are used in tropical cyclone (TC) track forecasting. The analytic function are defined as the profile that the wind speed is maximum on the TC center (ventilation flow) and weakened with a radial distance from the center. The ventilation flow, which determines the beta drift, is estimated by the 6-hr TC movement vector calculated using the TC center position from RSMC best track. Because the asymmetric component that is the most essential element of TC motion is not contained in the idealized 3-dimensional axisymmetric bogus vortex, it is possible to form a more realistic TC structure in the global analysis and improve TC track forecasting by including the analytic beta gyre. Also, the analytic beta gyre can complement inadequate asymmetries of the global analysis. Results of preliminary tests with WRF model have presented that the bogus beta gyre has positive impact on TC track forecasting.