A severe storm happened around the Three Gorges Dam area at midnight on 15 April 2002,which is the typical convective weather occurred under the condition that the cold front invades into the southwest inverted trough.The instant wind force reached 11,and the rainfall was about 50 mm per hour.The Doppler radar detected the mature thunderstorm echoes possessing the features of mesocyclones(V-pattern notches).The reinforced echoes maintained about 4 hours.According to the local records of instantaneous gusts,it is deduced that there might be strong downdraft currents near the surface,which led to catastrophic gusts.The energy of the strong gusts might come from the unstable convective energy accumulated in the middle troposphere,which is strongly indicative of the intensity of catastrophic gusts near the surface.It suggests that the strong gusts burst out when the unstable layer disappears.Different from other examples,the strong gusts and heavy rain in this case happened about one hour later of the occurrence of the strongest echo,highest echo top and largest vertically integrated liquid water content.The temporal lag can be the most important reference for weather forecasters to predict severe weather.