Barotropic Vorticity / Rossby Waves
∂ζ/∂t + U·∂ζ/∂x + β·∂ψ/∂x = F − rζ. Rossby phase speed: c = U − β/K².
When U < β/K² the wave is stationary — jet meanders. Blocking occurs when
high-amplitude Rossby waves become stationary, trapping weather systems.