Abstract: Based on the conventionally observational data and the NCEP data, a heavy snow process during November 9-12, 2009 in Shijiazhuang was diagnosed. The results indicate that the heavy snow process is related to upper western trough, southern trough in the south of Hetao area and shear in the middle and lower level. The vertical allocation of the upper and lower level jet is favorable to the strengthening of ascending movement in the heavy snow area. The ascending area is always located in the divergence area on the right side of upper westerly jet and the convergence area in the front of left side of lower southwest jet exit, and the northwest jet in the north of 700 hPa plays a very important role to the strengthening of the heavy snow. The ascending region has a better correlation with the positive vorticity field, and both locations of the strongest ascending region and positive vorticity center are consistent. The better correlation between the ascending motion and humidity field is important to the occurrence and reinforcement of the heavy snow. There exists a high relative humidity (about 90%) column from the surface to 200 hPa over Shijiazhuang. The south warm-wet southwest air airflow from the southwestern and the wetter stream of the Bohai bay from the northeast return streamer are the source of energy and water vapor.

Key words: Snowstorm, Circulation situation, Diagnosis analysis