Investigation of Tropical Cyclone Translation Speed with Clustered Tracks

The slowdown of tropical cyclone (TC) translation speed leads to prolonged coastal exposure, resulting in increased TC precipitation accumulation and possible exacerbated risk of compound flooding in coastal regions. In this study, spatial and temporal variations of TC translation speed in the western North Pacific are investigated, utilizing the CMA-STI best-track dataset spanning from 1949 to 2022. The annual-mean translation speed exhibits divergent trends, which are highly sensitive to the selected data period. However, the translation speed over land consistently shows a declining trend. Considering the strong correlation between TC track patterns and atmospheric circulations, TC clusters were identified by k-means method based on decay positions. Straight-moving and recurving TCs exhibit distinct characteristics in terms of frequency, landfall ratios, genesis locations, and translation speed. Representative recurving TCs tend to move faster when they have decay positions farther to the east. The positive trend of translation speed since the late 1970s is driven by track density variation from two main aspects. First, there is a decrease in the track density of lower-latitude TCs. Second, there is an increase in the track density of higher-latitude TCs with larger translation speeds. This study highlights the importance of understanding the changes in TC translation speed and its potential implications for coastal regions. By identifying the patterns and trends, we can better prepare for and mitigate the impacts of TCs in the future.