By using the Doppler radar data of the hail event April 12, 2003 in Jiangxi province, the development characteristics of severe convection weather are analyzed and several respects and indexes are put forward about nowcasting of severe convection weather. It's concluded that the bow echo, TBSS, adverse wind regions, low-layer mesoscale convergence line, VIL and the change of hail index can used for nowcasting of convectional weather.