theory on the funnel structure of tornado
龙卷风的漏斗结构理论

Tornado is a small-scale system which as the maximal horizontal and vertical velocities in the atmosphere. From the governing equations satisfying the balance between pressure gradient force, inertial centrifugal force and viscous force, the three-dimensional velocities of tornado are obtained, and then its funnel structure is depictured theoretically. It shows that the funnel structure consists of vertex flow and jet flow. The vortex flow is resulted from inertial centrifugal force and the jet flow is from strong convection by the horizontal convergence. At the same time, it indicated that tornado is formed under the exceedingly unstable atmospheric stratification conditions.