Abstract: An infrequent snowstorm occurred over a zone from Usu to Shihezi in the central part of northern piedmont of the Tianshan Mountains, Xinjiang, China during February 22-23, 2010. The snowstorm resulted in a serious economic loss, especially in facility agriculture, traffic, electric power and peopl[JP8]e’[JP]s daily life. In this paper, the NCEP/NCAR 1°×1° 6 h reanalysis data and the synoptic diagnostic method were used to analyze the circulation and physical quantity of the infrequent snowstorm weather. The results showed that the snowstorm occurred under an interaction of shortwave of strong frontal zone in periphery of the vortex and the south branch trough. The vertical structure of low-level convergence and upper-level divergence promoted the air rise and the aggregation and uplift of low-level warm air, and provided the trigger conditions of energy for snowstorm formation, occurrence and development. The snowstorm intensity and duration was positively correlated with the intensity, thickness and relative humidity of ascending motion, which is an indication for estimating the occurring time and spatial distribution of snowstorm in the study area.

Key words: snowstorm, diagnostic analysis, vapor flux, relative humidity, temperature advection, central Tianshan Mountains, Xinjiang