baroclinic instability

A hydrodynamic instability arising from the existence of a meridional temperature gradient (and hence vertical shear of the mean flow and a thermal wind) in an atmosphere in quasigeostrophic equilibrium and possessing static stability.

For reasonable values of the atmospheric parameters, the wavelength of maximum instability corresponds to that of a synoptic-scale disturbance. Such a system may be interpreted as converting potential energy of the basic flow into kinetic energy of the unstable perturbation.
Holton, J. R. 1992. An Introduction to Dynamic Meteorology. 3d edition, Academic Press, . 228–264.

1. The study of the physics, chemistry, and dynamics of the earth's atmosphere, including the related effects at the air–earth boundary over both land and the oceans. Fundamental topics include the composition, structure, and motion of the atmosphere. The goals ascribed to meteorology are the complete understanding and accurate prediction of atmospheric phenomena.