Warning characteristic and trigger mechanism of a local strong hailstorm in northern He′nan province

Based on the conventionally meteorological observation data,Doppler radar data,satellite data,meteorological data from regional automatic weather stations and the NCEP reanalysis data,the forewarning characteristic and trigger mechanism of a local strong hailstorm occurred on June 11,2011 in the northern He′nan province were analyzed.The results show that the local severe convective weather occurs under the background of the northeast cold vortex,and the potential area of severe convective weather is located on the right side of the junction areas of upper and lower mesoscale synoptic system(trough,sheer line,the axis of larger wind speed).The CAPE values are large and the vertical wind sheer from 0 km to 6 km determined from the revised sounding data before the local severe hailstorm weather happens is moderate or strong,which facilitate the formation and development of supercell.The convective instability of atmosphere increases while the cold advection in upper level moves southward and the warm advection in lower level moves northward.The meso-β-scale convective cloud cluster is generated in the rear of the northeast cold vortex and its development and evolution have some certain reference values for weather warning.Strong convective echo goes through the developing stage with cell shape to band shape and the weakening stage with block shape.The supercell generated on the south of the convective echo-belt results in the characteristic of ′three-body scattering′ when the local severe hailstorm weather appears.The cold air and surface convergence lines are the important trigger mechanisms for severe convective weather,and the surface convergence lines are indicative for strong convection weather.