Tropical cyclone prediction using a barotropic model initialized by a generalized inverse method

Abstract

A nested, nondivergent barotropic numerical weather prediction model for forecasting tropical cyclone motion out to 48 h is initialized at time t = 0 by assimilating data from the preceding 24 h. The assimilation scheme finds the generalized inverse of the model and data for -24 ≤ t ≤ 0. That is, the inverse estimate of the streamfunction is a weighted least-squares best fit to the initial conditions at t = -24, to the data at t = -12 and t = 0, and to the dynamics and the boundary conditions in the interval -24 ≤ t ≤ 0. In particular, the dynamics are imposed only as a weak constraint. The inverse method was tested on ten cases from four different tropical cyclones observed in the South China Sea during the 1990 Tropical Cyclone Motion Program (TCM-90). Predictions of cyclone tracks out to 48 h were compared with the Australian Weather Bureau's operational barotropic model which has no data assimilation procedure, and with a simple nudging scheme. In the latter, a model integration from t = -24 to t = 0 is nudged toward target analyses at t = -12 and at t = 0. -from Authors