Timeline

Sep 2011 - Jun 2014

Description

This project investigates the structural evolution and environmental conditions of tropical cyclones (TCs) during extratropical transition (ET) over the western North Pacific, as well as the formation processes of initial tropical disturbances.

Using cyclone phase space (CPS) analysis, 58 ET cases from 2000-2008 were examined, revealing that stronger TCs are more likely to undergo ET, which typically lasts around 28 hours and involves increasing thermal asymmetry and the development of upper- and lower-level cold cores. Composite analysis showed that TCs gradually transition into extratropical cyclones under the influence of mid-latitude baroclinic systems, characterized by enhanced potential vorticity gradients and moisture transport.

Complementing the ET study, the formation of Typhoon Fung-Wong (2008) was analyzed using FY-2C satellite data and reanalysis datasets. Results showed the initial disturbance developed in a saddle-type field with strong vertical wind shear that later weakened due to upper-level circulation adjustments. Convection near the upper cold vortex and the evolving subtropical high created favorable conditions for cyclogenesis, marked by the descent and intensification of low-level vorticity. Together, these findings highlight the critical roles of both large-scale environmental forcing and internal structural changes in TC formation and transition dynamics.

Publication

  • Wei, G.F., Zhu, P.J., Jiang, J. and Liu, H.J., 2017. Analysis of Structure Evolution and Environmental Conditions of Tropical Cyclones Over the Western North Pacific During Extratropical Transition. Journal of Tropical Meteorology, 23(1). Link
  • Jiang, J., Zhu, P.J., and Jiang, J., 2016. The Formation and Structure Evolution of Initial Disturbance of Typhoon Fung-Wong (2008). Journal of Tropical Meteorology, 22(1), pp.1-10.. Link