Study of South China Sea typhoons between 1999 and 2002

South China Sea Typhoons between 1999 and 2002 were studied using the MM5 model system. As an example, South China Sea typhoon Leo was studied in detail using the model system. Vorticity budget analyses were carried out to study the dynamics of the typhoon formation.; A Balanced Tropical Cyclone Bogus scheme is presented to improve the representation of a tropical cyclone in the initial condition of a mesoscale model. The vortex formed by this method is asymmetric and well adapted to the prediction model. It can be easily used in an operational system.; The effect of two South China Sea tropical cyclone interactions on the track of them was numerically studied using the MM5 numerical model system with the balanced tropical cyclone bogus scheme. Numerical studies confirmed that the abnormal track of South China Sea typhoon Maggie is a result of its interaction with another South China Sea disturbance.; Impacts of the different cumulous parameterization scheme on the Leo simulation were also tested. Numerical experiments showed that the Betts-Miller scheme is better than the Grell scheme in the South China Sea typhoon simulations.