Abstract:Based on the Tianjin Doppler radar data, conventional observation, ground automatic station meteorological data, ERA5 reanalysis data and VDRAS data, a rare heavy precipitation(HP) supercell storm which was guided by a multi-cell strong storm occurred in the eastern Hebei on 19 June 2017 was analyzed, the evolution characteristics and maintenance mechanism of supercell storms are mainly discussed. The results indicate that the sea-breeze front and the gust front of the multi-cell strong storm provide better dynamic conditions, the high temperature and high humidity area of tongue shaped by sea-breeze front and the gust front in the lower layer surrounding provide better thermal conditions for the formation of the supercell, when the convection cell moves into the tongue area, then it rapidly develops into a supercell and moves southeastward along the outflow boundary of multi-cell strong storm. The relatively stable gust front provided by the slowly weakening severe thunderstorm not only provides long-term thermodynamic conditions for the development and maintenance of supercell, but also guides its movement, which is of great significance for the short-term and imminent warning of the convective weather. At the beginning of the formation of supercell, affected by the outflow of multi-cell strong storm cold pool, the southerly winds near the ground turn to stronger easterly winds, the configuration of mesoscale environment has changed significantly, the vertical wind shear of 0~6 km increases to 27 m.s-1 and the shear of 0~3 km increases to 17~19 m.s-1 is the main reason for the rapid formation of mesocyclone, Secondly, the strong vertical vorticity advection on the convergence line is also conducive to the formation and maintenance of mesocyclone. The reason why the cyclone in supercell started at the lower level is that the vertical wind shear of 0~3 km obtained from VDRAS data is always about 20 m.s-1, the oblique vortex effect is obvious which provides a large and long-term horizontal vorticity input for the development and maintenance of supercell. During the formation and development of supercell, the relative helicity (SRH) of the storm is between 140 and 171 m2.s-2, which is more than 150 m2.s-2 for most of the time, Before the formation of supercell and near the dissipation stage, the SRH is significantly smaller, which is less than 150 m2.s-2 for most of the time, that indicates the SRH has a clear indication for the occurrence and development of supercell. The outflow of the cold pool precedes the formation of the supercell, which strengthens the convergence and uplift of the inflow, and is conducive to the development and maintenance of the supercell, In addition, there are more cells splitting from parent storm, which to some extent weakens the strong development of the supercell, but it just makes the sinking outflow not too strong and causes the gust front to move away quickly, making the cold pool always maintain a certain intensity, at the same time, the front of multi-cell storm provides a stable vertical wind shear of 0~3 km (maintained at about 20 m.s-1) for the supercell, this results in a long-term balance between the wind shear and the strength of the cold pool, and finally the supercell maintains a stable state for a long time. In a word, the main reason why the supercell maintains self-organization for a long time is that the appropriate vertical wind shear provided by the mesoscale environment keeps balance with the development of the storm.