Based on the MM5 3D-Var cycling system, a typhoon bogus and relocation scheme is designed and tested with a super Typhoon Rusa (2002) in South Korea. The bogus low/vortex, as well as other types of observations (e.g. radar data), can be incorporated directly into the 3D-Var cycling procedure. The typhoon bogus scheme with 3D-Var cycling procedure can relocate the predicted typhoon in the previous cycle to the right position for the next cycle of initialization and prediction.

The typhoon bogus scheme separates typhoon into symmetric and asymmetric parts. The construction of typhoon symmetric part is based on the typhoon report (e.g. central sea level pressure and radius of 15 m/s winds). The typhoon asymmetric part comes from the 3D-Var first-guess fields (previous prediction for the 3D-Var cycling system). To avoid double vortices in the analyzed field near typhoon area (one from 3D-Var first-guess and another from the bogus data), a removal procedure is applied to the 3D-Var first_guess field before 3D-Var minimization. Numerical experiments indicated that the designed typhoon bogus and relocation scheme can improve the prediction of typhoon track and intensity. Sensitivity studies of the designed scheme to the 3D-Var cycling assimilation window, specification of errors of the typhoon bogus data, and incorporation of other observations in the 3D-Var cycling procedure will be addressed.