The Role of Monsoon Trough on the Rapid Intensification of Typhoon Vicente (2012) in South China Sea

Tuesday, 19 April 2016
Plaza Grand Ballroom (The Condado Hilton Plaza)
Xiaomin Chen, Nanjing University, Nanjing, China; and Y. Wang, Z. Kun, and D. Wu

Typhoon Vicente (2012) underwent an extreme rapid intensification (RI) just before making landfall in the northern South China Sea. The important features of Vicente, including the extreme RI process, the sudden deflection, TC inner- and outer-core structures and spiral rainband, have been successfully reproduced in the Advanced Weather Research and Forecasting Model (ARW-WRF) simulation. The evolution of axisymmetric inner-core radar reflectivity and primary circulation of the simulated Vicente before landfalling are quantitatively compared with radar observed reflectivity and retrieved circulation from MGBVTD method (Modified Ground Based Velocity Track Display). The results show that the evolution of simulated axisymmetric inner-core structures are consistent with to their observed counterparts.

It is found that the RI of Vicente consisted of two Stages: (I) asymmetric Stage (i.e. RI onset), represented by relatively slow intensification associated with a distinct eyewall contraction; (II) axisymmetric Stage with slight eyewall contraction but efficient storm intensification. Results from a system-scale tangential momentum budget indicate that the primary spinup mechanism during Stage I is the radial eddy momentum transport, which is beneficial to accelerate primary circulation within radius of maximum wind (RMW) and eyewall contraction. In contrast,the principal spinup mechanism during Stage II is mainly ascribed to the forced secondary circulation in the response of diabatic heating within eyewall and boundary layer friction, which efficiently advected the absolute angular momentum radially inward and vertically upward to increase the primary circulation around the eyewall region throughout the troposphere. Further budget diagnosis based on scale separation reveals that the interaction between large-scale environmental circulation and vortex-scale vorticity anomalies has dominated the role of primary spinup mechanism during Stage I.

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