Reasons for Different Predictability of Tropical Cyclone Tracks in the Western North Pacific and Atlantic Oceans

Abstract Recent several studies have focused on the predictability of tropical cyclone track forecast. As a response to the question issued by Landsea and Cangialosi about whether “the approaching limit of predictability for tropical cyclone (TC) track prediction is near or has already been reached,” Zhou and Toth (hereafter ZT20) and Yu et al. (hereafter Y22) have found that the limit of predictability for TC track prediction has not been reached in both the Atlantic (ATL) and western North Pacific (WNP) basins. However, the predictabilities are different in the two basins, as ZT20 found that 1 day’s improvement can be obtained through 10 years in ATL, while Y22 found that 2 days’ improvement can be obtained through 15 years in WNP. To reveal the causes of this difference, the predictability of TC track in WNP is first investigated under the same framework as ZT20. Then, important parameters that determine the predictabilities are found and analyzed. Results suggested that the growth rate of true track forecast error in WNP is higher than that in ATL, indicating a lower predictability in WNP. Further explorations suggested that TCs in the WNP basin have averagely larger sizes, stronger intensities, lower-latitude locations, and poorer forecast skills of their guided flows. All these factors contribute to the larger track forecast error growth rate. Moreover, it is pointed out that the improvement of forecast skills over years is mainly due to the reduction in initial analysis errors; although a lower predictability is found in WNP, the forecast skill improvement in WNP is faster than that in ATL. Significance Statement Apart from its theoretical appeal, the predictability of tropical cyclone (TC)’s track is of practical interest to the forecast community and a seasonal concern for tens of millions of potentially impacted coastal residents. An investigation into the reasons for different predictabilities in the western North Pacific and Atlantic oceans would help the government to make allocation decisions for research and development investments associated with future TC forecast improvements.