Based on the routine upper-air and surface observations, temperature of brightness blackbody (TBB) from FY-2G/2E satellite, Doppler weather radar data and reanalysis data from ERA-Interim, we have conducted the diagnostic analysis of a severe convective weather event occurred in the Nanling Mountains from April 17 to 18 in 2016. Results are as follows. (1) Affected by inverted trough and convergence line at ground level, warm area precipitation occurred in the preceding stage of this event, and then frontal precipitation turned up rapidly in the later stage of this event with surface cold air mass intrusion and southeast-moving of low-level shear line and high level trough. The short-time strong rainfall zone tallies well with the trend of the Nanling mountains, and extremely heavy rain is caused by several mesoscale convective systems (MCS) and topographic forcing effect. High-echo-centroid short-time strong rainfall, thunderstorm gales and big hailstone occurred mainly in the warm area precipitation stage. After the front passed over mountain, low-echo-centroid short-time strong rainfall occurred but thunderstorm gales and hailstone seldom occurred. (2) Mesocyclone, high vertically integrated liquid (VIL) value, overhang echo and BWER observed in the radar echo map can provide important indicative features for the early warning of big hailstone, in which midaltitude radial convergence (MARC) is the key feature for the alerts of thunderstorm gales. (3) Deep dry layer at upper levels and high humidity at lower levels are favorable to the generation of big hailstone, and strong vertical wind shear between 0 and 6 km is favorable to the enlargement of hailstone. The large value of downdraft convective available potential energy (DCAPE) is a reference index for the forecast of thunderstorm gales, and the total layer dew-point depression and the small value of DCAPE are the reference basis to judge the occurrence of only short-time strong rainfall. (4) Bell-mouthed and windward direction topographic effect in the Nanling Mountains and its surrounding areas is conductive to the convergence of air flow in the low-level that triggers convection, causing the large frequency of heavy rainfall and the long lasting of precipitation. The frontogenesis in leeward side of Nanling Mountains increases the possibility of thunderstorm gale, hail and other weather in the southern foothills of Nanling Mountains.
WANG Donghai, et al
.2018. Diagnostic analysis of a severe convective weather event in the Nanling Mountains during the pre-rainy season[J].
Torrential Rain and Disasters, 37(6): 511-521.