Analysis of a continuous heavy rain event in Shaanxi produced by a low vortex

Using MICAPS data, ERA-Interim 0.25°×0.25° global high resolution reanalysis data, hourly surface observation data, FY-2G satellite cloud picture and CR/CB radar data from Yulin, a comprehensive analysis was conducted for an extreme heavy storm rain event occurred in northern Shaanxi province from 20:00 BT 25 July to 08:00 BT 26 July 2017. The results are as follows. (1) The heavy precipitation event exhibited a clear east-west zonal distribution, with slow moving high rainfall during a long time period in a small area, and mainly concentrating at night. Typical beta mesoscale characteristics showed in areas of heavy rainfall. (2) The westerly trough moved rapidly eastward and pressed down to the south. The stable maintenance of western Pacific subtropical high pressure favored the strengthening of the positive vorticity advection in front of the trough and the development of a low-value system in the surface layer. The nascent Hetao vortex at 850 hPa and southeast low-level jet are the direct impact systems