Comprehensive Analysis of a Severe Hail in the Middle Section on Northern Slope of Tianshan Mountain in Xinjiang

Based on the conventional data,the NCEP reanalysis data,the data of automatic weather station and the CINRAD /CC data in Shihezi,a severe hail event occurred in the middle section on northern slope of Tianshan mountain in Xinjiang on 11 July 2010 was analyzed. The results show that this hailing process happened under Balkhash Lake vortex circulation background. Favorable vapor conditions,unstable convection,suitable height of 0 ℃ and -20 ℃ layers and strong vertical wind shear promoted the generation and development of severe convection weather. Meanwhile,the special terrain and thermal instability at the border of the mountain and plain played an important role in triggering convective storm and further forming hail storm. Through the analysis of the Doppler radar products PUP: on the combined reflectivity factor( CR) chart,there was a strong convective cell where the echo was more than 50 dBZ and the intensity of echo was 63 dBZ in the center. The reflectivity section( RCS) showed the height of 60 dBZ strong echo had run up to 5 km as well as the height of 50 dBZ strong echo up to 7. 3 km,and there was a strong echo wall with the top reaching to 12 km. The height of 50 dBZ strong echo was much higher than the -20 ℃ layer height,which was beneficial to the formation of hail. On the average radial velocity maps,there was a mesocyclone before the hail coming,which maintained and strengthened convective storm. And there were convergence at the lower level and divergence at the upper level in the hail area. The leap increase of VIL and the density of VIL more than 3. 5 g·m-3 were the good condition for the hailstorm formation.