trajectory

(Or path.) A curve in space tracing the points successively occupied by a particle in motion. At any given instant the velocity vector of the particle is tangent to the trajectory. In steady- state flow, the trajectories and streamlines of the fluid parcels are identical. Otherwise, the curvature of the trajectory K_T is related to the curvature of the streamline K_S by

where V is the parcel speed and ∂ψ/∂t is the local change of the wind direction. The curvatures and wind change are positive for the cyclonic sense of flow.