Analysis of Environmental Conditions and the Structure of Radar Echo for a Supercell Splitting Process in the Midwestern Shandong Province

Based on conventional observation data, in this study, we analyzed Jinan Doppler weather radar data, FY-2G data, and automatic weather station data with respect to the formation and splitting processes of a supercell storm that occurred in the background of a cold vortex in North China on June 14, 2016. The radar echo characteristics and environmental conditions of the splitting supercell were analyzed in particular detail. The results showed that the supercell storm occurred near the mesoscale convergence line on the ground, in front of the centrally located short-wave slot trough. In an environmental condition characterized by hollow jets at high altitudes, which triggered an easterly moving convective cloud cluster, unstable layers, and strong vertical wind shear, the convective storms split, with those that were right-shifting strengthening. After splitting, the storm monomer on the left side of the environmental wind was not significantly restrained. The dew-point front near the mesoscale convergence line offset the resistance of the anticyclonic storm, which strengthened and extended the life of the anticyclonic storm. The storm monomer on the right side of the environmental wind was strengthened and lasted 2 h. The storm splitting process began at the initial stage of monomer formation, with the split initiating at the middle and upper levels and then extending downward. After the division, relative to the direction of the environmental wind, the left monomer was an anticyclonic leftward-moving storm, and the right monomer was a cyclonic rightward-moving storm. The cyclonic rightward-moving storm featured an inflow notch at the low level, a bounded weak echo region at the middle-upper level, and strong storm-top divergence at the upper level. These echo features are similar to those of a classic supercell storm. After the division, the rightward-moving storm was accompanied by a deep and long-lasting mid-cyclone that had originated at the middle level (four to five kilometers), and then developed both upward and downward. Its strongest rotation occurred at a high level with a rotation speed of 29 m/s. This differs from the behavior of the classic supercell monomer, which has its strongest rotation in the middle level.