Recent decrease in western North Pacific tropical cyclone rapid intensification during June

This study investigates the long-term tendency in ratio of rapid intensification (RI) cases to total number tropical cyclone over western North Pacific (WNP) during June between 1982 and 2021. There is a significant decreasing trend RI June, which opposite increasing July–November. From 1982–2005 2006–2021, significantly decreases region 5°–20°N 120°–150°N, while showing weak changes other parts WNP. Over with reduction, reduced 850-hPa relative vorticity 200-hPa divergence enhanced 850 vertical wind shear are likely primary drivers. The RI-suppressing effect above dynamical variables exceeds RI-favoring warming ocean, for example, increased sea surface temperature heat potential, this same region. Moreover, dynamic conditions can be related an anomalous low-level anticyclonic circulation, upper-level convergent flow greater enhancement easterlies than lower-level easterlies. Our highlights importance (e.g., shear) modulating WNP activity.