A unified three-dimensional instability theory of the onset of blocking and cyclogenesis

The instability characteristics of three-dimensional flow typical of the N Hemisphere average winter troposphere are examined in a two-layer spherical quasigeostrophic model. It is argued that the slow-moving dipole structures that occur in the Pacific and Atlantic Oceans when the model atmosphere is less unstable than usual, correspond to the onset of blocking, just as the fast moving monopole structures in the most unstable case correspond to cyclogenesis.-from Author