The effect of a hail suppression by anti-hail gun which occurred on June 25, 2005 in the east part of the Qilian Mountain was analyzed by using the CINRAD/CC products, including the layer composite reflectivity factors, the maximum values of the vertical reflectivity, echo tops, the horizontal wind field in the hail cell, the vertical structure and the maximum values of VIL, their changes before and after the hail suppression, as well as ground precipitation. Results show: (1) There are two aspects of hail suppression effect by anti-hail gun: The first is that silver iodide crystals sprinkle fleetly around the explosive point, and collide with the surrounding frozen droplets, reducing the average quality and diameter of frozen droplets; the second is that the power from shells exploding suppresses the developing of the updrafts under the explosive point. (2) The hail suppression by anti-hail gun is available for rainfall increase on ground. As for this hail suppression process, assuming that liquid water in the hail cloud falls completely as raindrops to the ground, the precipitation on the ground will increase 4.69%.

:Based on May to September weather cases during recent 10 years, together with the geographic information and the distri-
bution of hail storms weather and climate in Lanzhou,applying the products of the upper and surface observation and the numerical
weather prediction et al.,the weather forecasting methods for hail storms in Lanzhou are formed.The forecasting object is hail storms
at anywhere in the area, the principle is no failed forecast in 24 hours, the identification of the hail storms is according to methods of
the combination of the automation and man-computer interaction. These methods mainly provide the early warning and forecasting
information for hail prevention operation. We successfully forecasted two local hail processes by this operational forecasting system in
May in 2004, and the forecast accuracy reaches about 67%.