A New Approach to Diagnose Tropical Cyclone Track Prediction Error

In this study, the JMA's global spectral model (JMA/GSM) is run from the ECMWF's initial conditions, which are available through the YOTC dataset, to distinguish TC track prediction errors attributed to initial conditions from those attributed to the NWP model. Verified TCs are 16 TCs in the western North Pacific from August to November 2009. The position errors are found to statistically reduce by about 10 % by replacing the original initial conditions of JMA/GSM with the ECMWF's initial conditions, and in some cases, the predictions are significantly improved. In such cases, the low wavenumber component (< T42) of the ECMWF's analysis is found to be important. In addition, the scenario of the observed track is captured by the JMA's Typhoon EPS (TEPS) that deals with initial condition uncertainties based on singular vectors. Meanwhile, there are cases where the change in the initial condition does not help improve the prediction while the prediction by the ECMWF's NWP model is accurate. In such cases, TEPS cannot capture the observed track, either, implying need for modifications of JMA/GSM and/or dealing with model uncertainties in TEPS.