ZONAL-INDEX TENDENCY EQUATION AND ITS APPLICATION TO FORECASTS OF THE ZONAL INDEX

Abstract

An equation is derived relating the rate of change of the integrated zonal-index to the poleward angular-momentum flux convergence. The validity of the equation and its utility in forecasting the zonal-index change are checked against observed cases, with good results. For the simple harmonic case, the equation is integrated and the solution compared with an observed example.