The Structure and Development of an Extratropical Cyclone over Northeastern Asia

The rare snowfall event in 2012 over North China due to the development of an unusual cyclone was analyzed. The results show that the cyclonic vorticity occurs first at the middle troposphere, and then extends to both the upper and lower troposphere. The trigger mechanism for the cyclone genesis is the baroclinic forcing with the upper unusual vorticity advection promoting its rapid development. The efficient deployment of the high- and low-level jets forms a favorable environment for its development and also transports a great number of vapor and the instability energy into the area of blizzard, resulting in the occurrence of the rare event.