Primarily for that reason, it continues to defy dynamical description. Strong turbulence occurs in atmospheres and oceans under conditions where the Reynolds number is large. The Kolmogoroff spectrum provides a simple scaling for three-dimensional, hydrodynamical turbulence. It describes how energy introduced at large scales cascades to progressively smaller scales ultimately to be dissipated by viscosity. Two-dimensional strong turbulence has a different dynamics.
Weak turbulence involves nonlinear interactions among waves.
Because individual waves survive for many periods, weak turbulence is amenable to standard techniques of perturbation theory. Ensembles of waves on the surface of deep water are among the best studied examples of weak turbulence. These interact via three-mode couplings which transfer energy towards shorter wavelength. As their name implies, gravity provides their restoring force. The lowest order, nonlinear interactions of gravity waves couple four modes.