5B.6 Evolution of multi-scale vortex in the development of Hurricane Dolly (2008)

Tuesday, 11 May 2010: 9:15 AM
Arizona Ballroom 2-5 (JW MArriott Starr Pass Resort)
Juan Fang, Nanjing University, China, Nanjing, China; and F. Zhang

Through the cloud-resolving simulation with the Weather Research and Forecast (WRF-ARW) model, this study examines evolution of multi-scale vortex in the development of Hurricane Dolly (2008). The high-resolution simulation indicates that the development of Hurricane Dolly evolved the multiscale interactions between system-scale, convection-cluster-scale and convection-scale vortices.

During the development of Dolly, the cyclonic vortexes in the convective scale were very active. It is found that the accumulation and release of convective potential available energy and increase and decrease of relative humidity usually occurred alternatively in the evolution of the vortexes with long life period. This indicates that these cyclonic vortexes not only contributed to the enhancement of the system vorticity but also play an important role in the moist convection activity. Along with the burst of convection, the anticylonic vortex was also prominent. These vortexes underwent an inward propagation under the effect of the large-scale convergent flow and then dissipated gradually. The expulsion of the negative vorticity suggested by the previous works on the tropical cyclone was not significant in the development of Dolly.

Although the convection-scale vortices were active, the energy in this scale did not exhibit distinct increase as the storm is intensified. In contrast, the energy of the convection-cluster-scale and system-scale perturbation demonstrated steadily enhancement along with the development of the storm. This implies that the energy produced by the convective processes was immediately transferred into larger scale. The spectrum analysis shows that the convection-cluster- and system-scale divergence is much smaller than vorticity in the most period of the developing stage of Dolly, which implies that the evolution of the convection-cluster- and system-scale vortices was controlled by the balance dynamics. It is speculated that the macro effect of the convection-scale perturbation is to act as a permanent forcing on the balance dynamic system. By this way, the energy produced by the convections was continuously transferred to the larger scale and then led to the development of Dolly.

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