The complexity of major vortex motion in a system where four scales are coexisting (a subtropical high ridge, the major vortex, meso- and small-scale vortices) is examined numerically using a barotropic primitive equation model. The microenvironment of a major vortex consists of a group of small-scale vortices in which varying values for the total number N of initial small-scale vortices (N = 2, 3, 4, and 5, respectively) creates a diverse range of microenvironments. Three kinds of major vortex motion are observed: (i) the initial major vortex decays away with no new major vortex formation; (ii) a weak new major vortex forms while the major vortex decays; and (iii) a new major vortex occurs, via self-organization, with its intensity and scale similar to those in the initial stages of the original major vortex, and this vortex continues to shift westwards after the old major vortex decays.