Abstract:An urban flooding was caused by heavy rainfall in Wuhan on 6 July 2016. Based on Doppler weather radar of Wuhan and surface automatic station observation, and EC 0.25°×0.25° fine-grid model data, the charactersitics of heavy rainfall, the evolution features of mesoscale convective system (MCS), the environmental condition and radar echo structure of Meiyu front are studied in this paper. The result shows that (1) the heavy rainfall event occurred under the circulation pattern of typical Meiyu period. The high temperature and high humidity areas on the northwest side of the subtropical anticyclone were stable with the Jianghuai shear line, and the heavy rainfall appeared in the convergence zone of the southwest low-level jet. (2) The train line was mainly composed of the mesoscale system near the Jianghuai shear line or boundary convergence line. The mesoscale cyclonic convergence and low-level southwest jet maintained a long time, which is the main reason for the formation of the “train effect”. (3) Heavy rainfall was a typical MCS, which moved along the southwest-northeast direction, and the special topography of Hubei reinforced the “train effect”. (4) The MCS has three distinct characteristics in radar echo. The first one is MCS in the radar echo pattern belongs to the band composed of stratiform and convective rain train line, consistent with the trend of the southwest airflow. The second is MCS moved in the direction of stratiform cloud and train lines were almost the same. MCS’s direction was parallel to the train line, and the component perpendicular to the train line is quite small. The third is the convective cells were newly born and strengthened in the upstream on the train line, moving downstream. The convective propagation direction and train line were in the opposite direction. (5) The southwest jet near the ground and bulls eyes intensified the precipitation.