Nonlinear instability and error growth in Northern Hemisphere three-dimensional flows: cyclogenesis, onset-of- blocking and mature anomalies.

The nonlinear interactions of an initial small amplitude instability mode with a three-dimensional climatological flow (for Northern Hemisphere, January 1978), on which it is growing, are studied in a multilevel nonlinear primitive equation model incorporating spherical geometry. Numerical experiments in which there is either constant or no forcing are considered. -from Authors