Radial distribution of deep convective clouds preceding rapid intensification of the tropical cyclones in the western North Pacific

This study investigates the radial distribution of deep convective clouds (DCCs) 24 hours prior to the rapid intensification (RI) of tropical cyclones (TCs) in the Western North Pacific. TCs are categorized according to the 24-hour future intensity change (ΔVmax), as follows: non-RI (ΔVmax < 30 kt), short RI (RI-S, ΔVmax ≥ 30 kt for less than a day), and long RI (RI-L, ΔVmax ≥ 30 kt continuously for at least 1 day). The study finds that TCs in the Tropical Storm phase are most likely to undergo RI, with RI-L TCs having the strongest convective activity and coldest DCC temperatures near the center, and the most rapid ΔVmax, 24-6 h prior to RI. Higher temperature difference and more rapid increase in DCC percentage in RIL TCs as compared to other categories, suggest that these storms experience a more efficient and rapid intensification process. Larger radius of maximum wind found for RI-L TCs provides more room for intensification, potentially allowing for a more gradual development of the storm’s inner core, prolonging RI, before reaching maximum intensity. The results of this study can be used to identify TCs that are more likely to undergo prolonged RI even before its onset.