Decreasing Translation Speed of Rapid Expansion Tropical Cyclones Over the Western North Pacific

Abstract The overall destructiveness of tropical cyclones (TCs) depends not only on their intensity but also on storm size and translation speed, which together determine the spatial extent and duration of impacts. However, variations in translation speed of TCs undergoing rapid expansion (RE) over recent decades remain poorly understood. Using multiple TC best‐track observations and reanalysis products, we revealed a significant decline in the translation speed of RE TCs over the western North Pacific during 1980–2024. This decline is driven by a shift in RE occurrence toward slower‐moving TCs. Composite analysis indicated that decreased mid‐level relative humidity gradient, weakened low‐level radial inflow, and reduced relative sea surface temperature (SST) surrounding faster‐moving TCs are primarily responsible for this shift. By linearly removing the effects of climate variability and long‐term SST trend, we further demonstrated that the slowdown of RE TCs is influenced by both Pacific decadal oscillation and global warming.