It is difficult to forecast heavy precipitation under complex terrain in
mountainous areas, which formation mechanism is complicated, and often brings serious geological disasters. Based on
conventional observation data, European Centre
for MediumRange Weather Forecasts ERA5 reanalysis data, FY-4A satellite cloud
imagery, Doppler radar data and forecast
products from various models, the factors
contributing and model forecasting performance of local short-time heavy
precipitation process in the Hanjiang Basin of southern Shaanxi from the night
on 3 to the early morning on 4 June 2022 were examined and analyzed. The
results are as follows:(1) This process is a short-time heavy
precipitation triggered by the front in the Hanjiang Basin of southern Shaanxi.
Due to shallow convection instability and weak vertical wind shear, the heavy precipitation exhibited
localized characteristics with significant intensity. The accumulated
precipitation in 12 hours exceeds 50 mm in many stations, with a maximum of 104. 8 mm. (2) The two ends of
the front are blocked by the topography and move slowly and are difficult to
cross the high mountains. Consequently, convection is
continuously triggered within the basin, generating
heavy precipitation, and the
secondary circulation formed in the surface layer of the basin can enhance
convective activity. (3) A cold pool formed in the front of
front continuously triggers the backward propagation of new convective cells
within the basin to form a train effect. Meanwhile, the intense radar reflectivity factor, exceeding 50 dBZ, is located
below the 0 ℃ isotherm level, which
has high precipitation efficiency and prolonged duration, thus bringing a short-time heavy
precipitation with a maximum of 62. 6 mm·h-1 . (4) Global models
displayed limited capability in forecasting this process, while mesoscale regional models can reflect the
characteristics of frontal convection and precipitation, especially CMA-TRAM and CMA-GD models can reflect the triggering and development trend of local strong
convection well. However, the intensity
and organization of the convective system induced by the frontal cold pool of
the front still have substantial forecast deviations.