Abstract: A low-order spectral model is used to study abrupt change of quasigeostrophic current forced by both orography and diabatic heating.In certain parametric combinations,along with the gradual change of external thermal forcing,it is found that abrupt changes of both the spectral coefficients and the locations of the west jet stream can be stimulated.Introducing the orography into the model results in a change of the parametric range in which the multiple equilibrium of flow patterns exist and the shift of the parametric critical points at which the abrupt change of the locations of west jet streams is created,as well as an increase of the wave components of the equilibrium flow patterns.The aspects of simulated "South-Branch" jet streams are quite similar to the observational fact in the present of both the orography and the diabatic hearing than those in the case of the heating forcing.