Abstract:Conventional observing data, FY 2C satellite infrared and vapor pictures, auto station intensive surface observing data and new generation Doppler radar dete ction data were used to analyze an unusual “thunderstorm snow” weather event w hich happened from February 28 night to February 29 morning in 2008. The result indicated that the interact ion of southern trough, cold air and south west lower jet was the beneficial sy noptic background. The strong convection weather just happened in the baroclinic instability environment of humidity front with the interaction between jet and cold front. The meso γ scale convective cloud grew and gradually strengthened to meso β scale convective cloud which was the primary meso scale synoptic system and triggered this complex convective weather event. From the Doppler radar ech o picture we could see that the band echo with the shape of “人” and “hail sp ike” hook echo with the echo intensity of 25～33dBz, and gust front can also be detected from the PPI screen. And from the VPPI screen, anti wind area, lower l evel’s zero isotherm “S” warm advection and “bull′s eye” structure can als o be detected, which were classical features of meso scale convective system′s changing from weakness to strength during the period of rainfall evolving to ha il and snow in the “thunderstorm snow” weather. The fast evolving characters o f hourly surface temperature, pressure, relative humidity and wind showed the va lue of temperature, pressure and humidity increased before the thundersto rm happened, and the value of temperature and pressure got to maximum, and the p ressure curve appeared to dome shaped meso scale thunderstorm high pressure f eature. And any other else, the evolving of wind showed the wind rotated anti clockwise, and the northern wind velocity increased and the peak value app eared. When the thunderstorm passed, the meteorological factors showed th e temperature decrensing, and the humidity increasing, and the dew poin t temperature got to peak value.