A local high-velocity downward movement of air mass flowing out of a thunderstorm. It is the chief cause of severe wind shear. The size of a downburst may vary from a ¼ mile to more than 10 miles. It can last from 5 to 30 minutes. The wind speed can go as high as 120 knots. It is potentially very dangerous, especially during the takeoff and landing phases.
But the density of surface-observation sites remains coarse relative to the scale of MCSs and especially to the scale of sub-MCS features (e.g., mesoscale convective vortices or macrobursts) known to be responsible for much of the most intense damage within bowing convective systems (Miller and Johns 2000; Miller et al.