A faintly luminous streamer that creates the first path in a lightning stroke. It propagates downwards from the cloud in stages, each some 50 m long, with slight pauses between each step, sending out branches as it does so. When one of the branches nears an object on the ground, a return stroke carrying the main discharge follows the path of that branch, but in the reverse direction. See also dart leader.
Subjects: Meteorology and Climatology.