Understanding Rapid Intensification of Typhoon Mujigae in 2015: Insights From Kinetic and Potential Energy Budgets.

This study investigated the kinetic and potential energy budgets during the slow (SI) and rapid intensification (RI) periods of Typhoon Mujigae, which occurred in October 2015, by conducting a Weather Research and Forecasting model simulation. We found that the kinetic energy conversion between asymmetric and symmetric rotational circulations in the lower troposphere plays a pivotal role in initiating the difference in the tendency of symmetric rotational kinetic energy between the RI and SI via the horizontal advection process of asymmetric circulations. Southerly and easterly environmental flows transported asymmetric anticyclonic flows in SI and cyclonic flows in RI to the radius of maximum wind, respectively, where asymmetric rotational circulation was developed by vertical shear of environmental flow. Such transports initiate the growth of symmetric cyclonic rotational circulation from SI to RI. The kinetic energy conversion of symmetric divergent circulations supported by symmetric potential energy accelerates the growth of symmetric rotational kinetic energy from SI to RI. These findings can shed light on the fundamental dynamics of the RI of tropical cyclones. Plain Language Summary: The rapid intensification of typhoons in the offshore areas of China often leads to severe economic losses after landfall. Accurate forecasting of rapid intensification can help improve governmental decision‐making to reduce these losses. Understanding the physical processes associated with rapid intensification is crucial to achieving this goal. In this comparative study, we analyzed modeling data from the slow and rapid intensification of Typhoon Mujigae, which occurred in 2015, to identify the key physical processes responsible for its rapid intensification. During this period, Mujigae moved northwestward from an area of southerly winds during slow intensification to an area of easterly winds during rapid intensification. Easterly winds provide favorable environmental conditions for initiating the growth of cyclonic circulation at the lower level. The conversion of potential energy into symmetric divergent kinetic energy accelerates the intensification of Mujigae through the interaction between convergence and cyclonic circulation. Key Points: The conversion between asymmetric and symmetric rotational kinetic energies determines the slow (SI) and rapid (RI) intensification of MujigaeThe radial advection of the azimuthal wavenumber‐1 rotational flow controls the conversion depending on the environmental circulationThe movement of Mujigae into an area of easterly winds accelerates the growth of symmetric rotational kinetic energy from SI to RI [ABSTRACT FROM AUTHOR]