Simulation Analysis of Typical Tornadic Supercell and Nontornadic Supercell Processes

Abstract:Based on the simulation of four-dimensional variational assimilation analysis system and the data of Doppler radar, conventional observation and encrypted automatic station, the processes of tornadic supercell in Funing, Jiangsu Province on June 23, 2016 and typical nontornadic supercell which induce gale and hail on April 28, 2015 are analyzed in detail.The results show that: (1) both processes are generated under the background of high-altitude cold vortex and ground warm low pressure. The environmental vertical wind shear and low-level is closely related to the development of the storm. In the early stage of storm development, the strong vertical wind shear in middle and low-level is conducive to the formation and development of supercells, and the strong vertical wind shear in the low-level is conducive to the formation of tornadoes.（2）Too strong cold pool will weaken the low-level inflow of the storm, but the strong middle and low-level vertical wind shear can offset this effect, so that the supercell can be maintained and further developed; When the environmental vertical wind shear weakens, the supercell also tends to weaken or even split and dissipate.（3）The large vorticity area of the tornadic supercell is first generated and developed in the middle and high layers. Then, with the continuous strengthening of the outflow of the weak cold pool and the vertical wind shear in the low layer, the large vorticity value center is gradually generated and strengthened in the low layer. At the same time, the mesocyclone bottom height and top height show a gradual downward trend. When the vorticity center drops near the ground and the mesocyclone bottom height drops to the lowest layer, the tornado occurs.（4）There is also large vorticity centers in the middle and high levels of nontornadic supercells，and develop to the low level.Under the influence of strong cold pool near the ground, the low-level vorticity can not be maintained for a long time or enhanced or even weakened, which inhibits the generation of tornadoes, but strong cold pool outflow can also produce gale weather .