Abstract
The Fjørtoft's graphical method of integrating the barotropic vorticity equation is developed under some approximate assumptions. By this method, the relaxation procedure or the Fjørtoft's approximate integration formulae for solving the Poisson type equation are not necessary. And farther, as the changes in Fjørtoft's “quasi-permanent velocity field” are considered by this method, the results of prediction may be improved and time intervals of prediction may be prolonged than the Fjørtoft's method.
A graphical procedure for the numerical weather forecast is derived and the results of its application for 12hrs, 24hrs and 48hrs forecast are also shown.
