The evolution of stratospheric polar vortices show various evolutional paths. We used an isentropic shallow water system with radiative relaxation and steady topographic forcing to investigate the sensitivity of the polar vortex evolutional paths to the forcing amplitude and wave number. Weak amplitude wave number 1 of bottom forcing leads to less violent vortex breaking during which filaments are shed in concert with edge sharpening. In this type of breaking only small amount of area loss occurs. Large forcing amplitudes lead to cycles of vortex core breakdown and recovery. Wave number 2 is less effective in edge erosion and sharpening but significantly more destructive to the vortex core. These asymptotic states are essentially associated to the different stages of the observed stratospheric polar vortices.