Numerical Simulation and Piecewise Potential Vorticity Inversion Analysis of an Extreme Explosive Cyclone over the Northwest Pacific Ocean in Early November of 2014

On the basis of the 6-hourly NCEP GFS (Global Forecasting System) reanalysis data with a horizontal resolution of 0.5°, an extreme explosive cyclone event occurred in early November 2014 is simulated using the WRF (Weather Research and Forecasting) model. After the key features of this extreme event are well reproduced by the WRF model, this study analyzes the environmental conditions favorable for the rapid development of the cyclone, and investigates the mechanisms for the explosive development of the cyclone using the piecewise potential vorticity inversion method. Main results are as follows:(1) The explosive development of this cyclone lasted for 27 h with a maximum deepening rate of 3.98 Bergeron (unit of cyclone deeping rate), and a minimum central SLP (Sea Level Pressure) of 919.2 hPa. (2) The rapid development of the explosive cyclone was closely related to heat transport by the upper-level jet stream in the upper troposphere, the quasi-geostationary forcing (e.g., warm advection and cyclonic vorticity advection) ahead of a shortwave trough in the middle troposphere and the warm advection accompanied by the warm front in the lower troposphere. (3) The result of piecewise potential vorticity inversion shows that the tropopause-folding-related downward transport of large-value potential vorticity in the stratosphere and the precipitation-condensation-related diabatic heating governed the rapid development of this explosive cyclone, while the baroclinic process in the lower troposphere made the smallest contribution. In the early and middle stages of the explosive development period, the latent heat release is the most important factor for the cyclone's development. In contrast, in the late stage of the explosive development period, because the precipitation weakened and the cyclone entered a strong tropopause folding region, the tropopause folding became the most favorable factor for maintaining the rapid development of the cyclone.