A Slowdown in Translation Speed of Western North Pacific Tropical Cyclones Undergoing Rapid Intensification

Abstract

This study examines long-term trends in western North Pacific (WNP) tropical cyclones (TCs) experiencing rapid intensification (RI) from 1971 to 2022. Although there is only a weak slowdown for all intensifying WNP TCs, the average translation speed for RI TCs has significantly decelerated over the RI main development region (7.5°–25°N, 115°–160°E). This slowdown is primarily due to increasing RI probabilities for slower-moving TCs. By contrast, the RI probability of faster-moving TCs remains virtually unchanged. These differences in RI trend probabilities between slow-moving and fast-moving TCs are primarily linked to a deepening of the WNP mixed layer. TC-induced sea surface temperature cooling tends to weaken when the mixed layer is deep. During the intensification stage, the deeper mixed layer is more critical for slower-moving TCs than for faster-moving TCs. Our findings suggest that RI probabilities for slow-moving WNP TCs may continue to increase in a future warming climate.