Relationship between Early-Stage Features and Lifetime Maximum Intensity of Tropical Cyclones over the Western North Pacific

Abstract

The relationship between early-stage features and lifetime maximum intensity (LMI) of tropical cyclones (TCs) over the Western North Pacific (WNP) was investigated by ensemble machine learning methods and composite analysis in this study. By selecting key features of TCs’ vortex attributes and environmental conditions, a two-step AdaBoost model demonstrated accuracy of about 75% in distinguishing weak and strong TCs at genesis and a coefficient of determination (R2) of 0.30 for LMI estimation from the early stage of strong TCs, suggesting an underlying relationship between LMI and early-stage features. The composite analysis reveals that TCs with higher LMI are characterized by lower latitude embedded in a continuous band of high low-troposphere vorticity, more compact circulation at both the upper and lower levels of the troposphere, stronger circulation at the mid-troposphere, a higher outflow layer with stronger convection, a more symmetrical structure of high-level moisture distribution, a slower translation speed, and a greater intensification rate around genesis. Specifically, TCs with greater “tightness” at genesis may have a better chance of strengthening to major TCs (LMI ≥ 96 kt), since it represents a combination of the inner and outer-core wind structure related to TCs’ rapid intensification and eyewall replacement cycle.

Decadal variation in the frequency of tropical cyclones originating in the South China Sea and migrating from the western North Pacific

“…Song et al (2018 studied standard deviation of LMI and found that the occurrence frequency of the strongest and weakest TCs around the world during 1999-2016 was greater than that during 1981-1998. Lu and Tang (2021) used a machine learning method to study the distribution of the LMI, which revealed that the circulation of high LMI is that lower latitude is embedded in the continuous band with high vorticity in the lower troposphere, and the circulation in the upper and lower troposphere is more dense. Recent studies have mainly focused on the characteristics of LMI in global regions or oceans, but few studies have focused on local small continental seas, such as the SCS.…”