The track, landfall, dynamic and thermodynamic and cloud-rain physical mesoscale structures and their evolution of typhoon HERB 1996 in 36h from 0000Z 31 July to 1200Z 1 August 1996 were simulated by using the non-hydrostatic mesoscale model MM5. This period covered the process of typhoon HERB landfalling at Taiwan and Fujian province.
Results show that the model successfully simulated the landfall process of typhoon HERB, revealed the most important characteristics of the mesoscale dynamic and thermodynamic and cloud-rain physical structure during its landfalling. The simulated typhoon track was close to the observation. The center of cyclonic circulation simulated at 0000Z on 1 August 1996 (24h integration) was located in shore near Fuqing, Fujian province at which the typhoon was reported to landfall two hours later. It shows that strong upward motion formed by low level convergence existed in the eye-wall and subsidence at the center of the eye. The wind field shows clear asymmetrical structure near the typhoon center. The cloud and rainband was screwtyped distributed around typhoon center, and constituted by meso-beta-scale rain cores. During the period of typhoon HERB staying near Taiwan, the lower cloud was developed in the eye region so that made the previous clear typhoon eye on the satellite pictures becoming fuzzy. The observations show the typhoon center was warm and moist, but the model simulations with higher space resolution show that in the mid-tropospheric region of eye wall, where existed strong upward motion and more cloud and rain water, it was more warm and moist than in the eye.
During the period of typhoon passing through Taiwan and later landfalling at Fujian, the track of model typhoon deviated about 30km northward (i.e., right-ward) because of the effects of the orography of the Taiwan Island, but the strength of the typhoon was not affected significantly. The amount of rainfall maximum on Taiwan in the 36 hours simulations was enhanced more than six times induced by the orographic lifting of Taiwan Mountains.