Changes in Tropical-Cyclone Translation Speed over the Western North Pacific

Abstract

The trend of tropical-cyclone (TC) translation speed is a hot topic recently. Changes in TC translation speed during 1949−2017 over the western North Pacific are analyzed using two best-track datasets here. The TC translation speed decreased during 1949−2017, but there was no significant trend after 1981. The TC translation speed also changes with latitude and intensity. In the tropical ocean, TC translation speed decreased by 5.9% during 69-year recording period. North of 23.5° N, the changes in translation speed is highly consistent with the latitude of TC occurrence. The translation speed of tropical depressions showed no significant trend during the period 1949−2017, but the translation speed of typhoons decreased over the 69-year recording period. The period 1949−1981 contributed most of the slowdown trend. There also was an increase in the frequency of typhoons with translation speed slower than 6 m/s. The decrease of translation speed of typhoons before 1981 was likely caused by the weakening of the summertime tropical circulation.

Keywords

• western north pacific
• tropical cyclone
• translation speed
• latitude of tc occurrence
• intensity