Abstract: The distribution of tropical cyclone (TC) track forecast errors in the northwestern Pacific Ocean were studied based on the Japan Meteorological Agency (JMA) 6-hour TC forecast data from 2005 to 2018. The relationship between track forecast errors and western Pacific subtropical high (WPSH) was also analyzed. The results show that the northeast and southwest displacements are the main track errors in all the 0, 24, 48, 72 h forecasts. The ratios of the northeast and southwest track errors to the total forecast numbers for the 24, 48, 72 h forecasts are 61.62%, 64.02%, 66.94%. There is significant difference in spatial distributions between northeast and southwest track errors. The former mostly occur around 16°N, and the latter around 24°N. Further analyzing the relationship between northeast-southwest biases and WPSH, it is found that 70% of northeast track errors occur to the southwest of the WPSH and about 60% of southwest track errors occur to the northwest of the WPSH. Compared to the WPSH in southwest track errors, the WPSH in northeast track errors has a more extensive area and a more northward ridge. The northeast forecast errors tend to happen in WPSH induced westward migration of TCs, and the southwest forecast errors tend to happen in WPSH induced northward migration of TCs.

Key words: northwestern Pacific Ocean, tropical cyclone, track forecast error, spatial distribution, subtropical high