Dynamic mechanism for the evolution and rapid intensification of Typhoon Hato (2017)

This study investigated the evolution of Typhoon Hato (1713) and analyzed the inner dynamics of its rapid intensification. The moving path of Hato was controlled by the southwestern part of the western Pacific subtropical high which extended westward significantly. Due to a relatively steady leading steering flow, the trajectory of Hato showed a straight ESE to WNW direction, leading to disastrous rainfall in southern Guangdong Province on 23 August before and after the landfall of the typhoon. In addition, Typhoon Hato exhibited a rapid intensification period from 3 to 13 o'clock on 23 August, with central wind speeds increasing from 35 to 48 m/s. This study mainly examined the inner dynamics of the development of Hato, especially its rapid intensification period. The regression analysis results showed that Hato was generated and developed under a TD‐type‐like wave. The coupled convection and vortex provided a favorable environment for the development of Hato. The analysis of the barotropic eddy kinetic energy (EKE) and latent heat flux further demonstrated this scenario. The results showed that the regions with a positive EKE tendency and strong latent heat release were consistent with the reach of and shifted westward with Hato. The EKE conversion was enhanced significantly on 23 August, with a maximum intensity observed over the northern South China Sea and southern Guangdong Province. The mean kinetic energy was largely converted to EKE, which, together with the great latent heat release, led to the rapid intensification of Hato. Observed path of Typhoon Hato (black line) marked with yellow dots at every observation location. Shadings represent the mean SST between 21 and 24 August. The typhoon symbols represent the intensity of Hato exceeding the strong tropical storm level. The solid black lines denote the geopotential heights of 5,880 and 5,920 gpm. The vectors denote 700 hPa horizontal winds exceeding 8 m/s.