A Synoptic Process Analysis of Rain to Snowstorm in Fushun in Feb. 2009

By using routine meteorological data,the circulation background,impact weather system,satellite cloud pictures and radar data of a rare history process of rain to snowstorm in Fushun on Feb.12-13 2009 were analyzed,then tested and interpreted the numerical forecast products.The results showed that the severe precipitation was produced in a trough of a ridge of a meridional circulation situation in Eurasian mid-high latitude.The 500 hPa north vortex,the south branch trough,the Jianghuai ground cyclones,the 850 hPa shear line were major influence weather systems.Severe precipitation occurred in favorable dynamic condition of the low-level convergence and high-level divergence.There were two low-level jets converging in Liaoning in the precipitation process which provided a plenty of water-vapour.Cold advection invaded from the lower deck,low-level convergence of cold air formed a strong front zone which provided the dynamic condition for the severe precipitation.Hot and humid instability energy of low-level supplied thunderstorms and strong precipitation with thermal conditions.In the process of precipitation forecast,the situation forecast and precipitation forecast of Europe and Japan were stable and accurate.Germany had smaller precipitation forecast in the pre-48 hours,close actuality in 24-hour forecast and larger precipitation order in the process of mesoscale forecasts.