Analysis on Doppler radar characteristic of grade F1 tornado in Haimen

By using the Doppler weather radar,routine and intensive observation data the process of a grade F1 tornado happened in Haimen of Jiangsu province was analyzed in detail.The results show that before the tornado there existed a long entrainment instability,a low LCL,a strong horizontal and vertical wind shear and a surface dry line which provides very good dynamic conditions for a convective system to develop a tornado.Bottom cool air intrusion and strong wind shear made a single convective cell easier to develop more rapidly.The downward strong echo center height,the descending VIL,the rapid development of the radial velocity of the wind field in cyclonic vortex are good indicators of early warning of tornado.Tornado in the development process,as a low mass center convective system,obviously differs from the hail,a high center of gravity convection system.Sudden downward of mesocyclone height and maximum wind shear height,a sharp contraction of cyclone size indicate that the tornado will occur soon.