Abstract: Winds obtained by tracking features in satellite water vaporimagery have been used to analyze the upper level outflow in the vicinity of mesoscale convection systems (MCS) along the Meiyu front. Two upper level outflow pat terns have been identified. The first is associated with an upper level mesoscale anticyclone, and the main upper level out flow is seen as a mesoscale upper level jet (mULJ) located to the east of MCS. This mULJ turned to the south and flow into the tropical easterly jet near 20 N, forming a secondary indirect vertical circulation to the south of Meiyu front. In this case, the forcing of the mid-latitude westerly jet is weak. The second kind of upper level outflow was generated just to the south of the extratropic westerly jet. The Meiyu cloud band is associated with an anticyclonic wind belt with mid-latitude westerlies to the north and subtropical easterlies to the south. The upper level out flow (mULJ) appeared as to be a branch of the westerly jet, which flows to the west. A secondary direct circulation is formed along this kind of Meiyu front. The vertical wind shear in the Meiyu cloud band was less than 1 m/(s·100 hPa-1). Weak ventilation in the vertical is helpful for the maint enance of MCSs along the Meiyu front. This primary upper level water vapor wind analyses confirmearlier numerical simulations, which show that the mUL J is the upper level out flow channel over the MCS in the Meiyu cloud band.