Wingtip vortices roll up in the wake of this U.S. Coast Guard C-130J. At the edge of a wing high-pressure, low velocity air is able to creep around the edge of the wingtip toward the low-pressure, high-velocity air atop the wing. This creates a swirling vortex that trails behind each wing, made visible here by the clouds entrained in the plane’s wake. Over time, these counter-rotating vortices will sink downward and break up due to viscosity and instabilities induced by their proximity. (via Aviationist)