Abstract:A local flash heavy rain process occurred in central Hebei Province in the evening of August 5, 2018, causing a flash flood and death of two people. The trigger and maintenance mechanisms of the flash heavy rain are analyzed using conventional observation data, ground automatic station data, NCEP reanalysis data, VDRAS data, FY-4 meteorological satellite and Doppler weather radar data. The results show that the flash heavy rain occurred under the control of the Western Pacific subtropical high at 500 hPa which was stronger and more northward than usual. Affected by the inverted trough of Typhoon Jongdari landing northward, the water vapor content above Hebei was abnormally abundant. The surface dew point temperature was as high as 28~29℃, and the atmospheric precipitable water deviated from the mean value by more than 4σ. In addition, the atmosphere was unstable and the environmental wind was weak, so the environmental conditions were conducive to the heavy rain. The physical processes leading to the torrential rain in three places in central Hebei were different. In the southeast of Bao-ding, the heavy rain was caused by the gust front moving southward and eastward to form a mesoscale convergence center, where thunderstorm cells merged, enhanced and propagated backward forming a quasi-stationary rain belt. The flash heavy rain in the west of Baoding was triggered by the enhancing easterly airflow in the boundary layer lifted by the windward slope of Taihang Mountain, where the echo maintained as a result of the cold pool formed by precipitation confronting with the easterly wind. The flash heavy rain in the northeast of Baoding experienced two stages: the north-south convective cloud belt and the east-west convective cloud belt, which was the heaviest precipitation at night. At 01:00 BT 6 August, the north-south convergence line formed by the south airflow strengthened at a low altitude (1500 m above the ground) on the east side of Baoding and the south airflow on the west side caused the north-south radar echo to develop. As the southeast airflow turned into a southerly airflow, the quasi-east-west-oriented warm shear line formed with the northeast airflow caused the echo to turn to east-west direction. The enhanced low-level south airflow at night dominated the strengthening and maintenance of the heavy rainfall echo in the northeastern part of Baoding, which was the key factor in determining the location of the flash heavy rain.