Abstract:
Using observation data from Yantai S-band dual polarization doppler weather radar, Rongcheng CINRAD/SA(China New Generation Radar, S-band) radar, sounding, surface meteorological stations,ERA5(ECMWF Reanalysis V5) and hail, tornado information obtained from field surveys, a severe hailstorm and tornado occurred on 1 Oct 2021 in eastern of Shandong peninsula is analyzed. The results are shown below.1) Compared to the climate mean-field, the northeast cold vortex of 500 hPa is strong, and the 850 hPa has continuous southward water vapor transport from south China to the west of northeast China on 1 Oct 2021,under the influence of a high altitude clod vortex and low altitude wind shear, the atmospheric thermal and dynamic conditions such as dry and cold in the upper troposphere, but wet and warm in the low troposphere, with strong vertical wind shear and convective available potential energy(CAPE), et al on the eastern Shandong Peninsula before the storm occurred, it’s very favorable for the occurrence of strong hail and tornadoes. The features of pre-storm low pressure, thunderstorm high pressure, and cold pool are obvious near the surface. (2)In the hail-fall period, the supercell features were very typical, with distinct hook-shaped echo and inverted "V" anterior inflow gaps in the lower layers, and vertical profiles showing distinct Bounded Weak Echo Region(BWER) and differential reflectivity(ZDR) column characteristics. According to the large hail information, statistics the median value of reflectivity factor(ZH),ZDR and cross-correlation coefficient(CC) was 48.7 dBZ,0.89 dB and 0.90 respectively. When tornado and large hail appeared on the ground, the maximum storm-top divergent outflow(STD) reached 71.5 m·s-1. (3)The cold pool airflow at the northern end of the Rear Flank Gusts Front (RFGF) and the south inflow on the pre-storm side form a strong vortex upward motion, resulting in an EF1-level tornado. The tornado occur at the tip of the hook-like echo, and large hailstones appeared on the north side of the inflow gap. (4)About 5 minutes before the tornado was found on the ground, the radar detected the Tornadic Debris Signature(TDS) features, the ZDR was as low as -0.1 dB, CC was as low as 0.81, and about at 11 minutes before the tornado genesis, the ZDR arc in the lower layer and the descending reflectivity core(DRC) in the rear flank side of the supercell was detected. Rongcheng and Yantai radars identified mesoscale cyclones and Tornadic Vortex Signature(TVS) about 22 min and 5 min in advance, respectively, which can provide an important reference for a tornado warning. (5)Based on the observational analysis, the schematic diagram of the low-layer air flow field and the tornado and large hail-falling area of the super monolithic storm is summarized.