Characteristics of Tropical Cyclone Rapid Intensification over the Western North Pacific

Abstract

This study statistically investigates the characteristics of tropical cyclones (TCs) undergoing rapid intensification (RI) in the western North Pacific in the 37 years from 1979 to 2015 and the relevant atmospheric and oceanic environments. Among 900 TCs, 201 TCs undergoing RI (RI-TCs) are detected by our definition as a wind speed increase of 30 kt (15.4 m s−1) or more in a 24-h period. RI-TCs potentially occur throughout the year, with low variation in RI-TC occurrence rate among the seasons. Conversely, the annual occurrence of RI-TC varies widely. In El Niño years, TCs tend to undergo RI mainly as a result of average locations at the time of tropical storm formation (TSF) being farther east and south, whereas TCs experience RI less frequently in La Niña years. The occurrence rates of RI-TC increased from the 1990s to the late 2000s. The RI onset time is typically 0–66 h after the TSF and the duration that satisfies the criteria of RI is 1–2 days. RI frequently occurs over the zonally elongated area around the eastern Philippine Sea. The development stage and life-span are longer in RI-TCs than in TCs that do not undergo RI. RI-TCs are small at the time of TSF and tend to develop as intense TCs as a result of environmental conditions favorable for TC development, weak vertical wind shear, high convective available potential energy, and tropical cyclone heat potential. The occurrence rates of RI-TCs that make landfall in Japan and the Philippines are higher than in China and Vietnam.

Is the Number of Tropical Cyclone Rapid Intensification Events in the Western North Pacific Increasing?

“…There is a discrepancy in the long-term RI occurrence trend between best track datasets for the western North Pacific (WNP) 1 . According to best track data from the Japan Meteorological Agency (JMA), both the number of TCs that underwent RI and the RI occurrence frequency increased from 1989 to 2015 (Ito 2016;Fudeyasu et al 2018). In contrast, best track data from the Joint Typhoon Warning Center (JTWC) indicate that the number of TCs that experienced RI during the active TC season (July to November) decreased slightly from 1989 to 2015 (Zhao et al 2018, see their Fig.…”

A Definition of Rapid Weakening for Tropical Cyclones Over the Western North Pacific

“…Ever since then, substantial work has been conducted to broaden current understanding of RI (e.g.,Chen & Zhang, ; Guo & Tan, ; Lee et al, ; Wang & Wang, ; Zhao et al, ). Favorable environmental conditions, such as weak vertical wind shear, warm ocean surface, and high low‐tropospheric relative humidity, as well as a large discrepancy from maximum potential intensity, have been identified to be crucial factors leading to the occurrence of RI events (Chang & Wu, ; Fudeyasu et al, ; Kaplan & DeMaria, ).…”

Understanding the characteristics of rapid intensity changes of Tropical Cyclones over North Indian Ocean

“…But since 2000, the correlation is 0.36. These statistics have clearly showed that a higher intensification rate was observed recently [4,10]. Figure 3 shows the TC distribution for both RI and RD cases, along with non-intensity changes.…”