A Numerical Study of Formation and Development of Intense Convection That Caused the Tornado in Blagoveshchensk on July 31, 2011
The results of the numerical simulation of intense convection that caused the tornado in the city of Blagoveshchensk on July 31, 2011 are presented. The WRF-ARW nonhydrostatic mesoscale model on the nested grids with the spacing to 500 m is used for simulations. It is found that the tornado was initiated by the meso-γ vortex associated with a quasilinear convective system at the height of 700-900 m. The mesovortex was generated when the wind shear in the lower 2-km layer was 21-27 m/s and convective available potential energy was to 1800 J/kg. The position and center of the mesovortex were specified by the values of vorticity and the Okubo-Weiss number. The simulated tornado was formed close to this mesovortex. The main contribution to the intensification of vertical velocity in the tornado was made by the perturbations of pressure and buoyancy and that to vorticity was made by the horizontal advection. The simulated time of occurrence, location, and duration of the event slightly differ from the real ones.