Based on the Fuyang Doppler weather radar data, the tornado that occurred in Yingshang County, Anhui Province on 23 July 2008 is analyzed in detail. It is shown that the storm is intensified rapidly after the continuous merging of storm cells, and becomes a supercell. The merger and interaction between the storm cells may be instructive for tornado warning for they are highly correlated to the time and location of the tornado. The mesocyclone and tornado vortex signature products with default parameters setting in CINRAD/SA radar system are indicative to tornado warning. When the two kinds of products are detected for the same storm simultaneously along with the observed bounded weak echo areas, the probability of tornado becomes even higher.