Storm Highway by Dan Robinson
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Does lightning travel upward or downward?

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The answer is BOTH: There are distinct types of lightning strikes to earth that can travel in either direction - cloud-to-ground lightning and ground-to-cloud lightning. For each of these types of lightning, current flow and leader development can also take place in both directions.

VIDEO: Does lightning go UP or DOWN?

Cloud-to-ground lightning: downward-moving

Lightning starts inside of a storm cloud in the form of a bidirectional leader with a positive end and a negative end. Both ends propagate and branch in opposite directions.

Fig. 1: A rendering of a lightning discharge after it starts and grows inside of a cloud. The bidirectional leader grows in opposite directions into regions of opposing charge. Here, the negative leaders are growing downward and the positive leaders upward.

For a negative cloud-to-ground discharge (the most common type of lightning striking the ground), the negative end of this bidirectional leader begins heading toward the ground. This stepped leader (the channel of ionized air) propagates downward. When the tip of the stepped leader approaches the ground, one or more upward-moving leaders initiate from the ground. The two opposide-moving leaders meet in midair, usually at a point about 300 feet or less above ground. When the stepped leader and leader meet, they provide a conducting path for charge flow, like a wire connecting the cloud and the ground. There is then a tremendous flow of current upwards through this established channel, brightly illuminating it.

Cloud-to-Ground Lightning animation Cloud-to-Ground Lightning photo

This animation depicts the stepped leader descending to meet the upward leaders extending from the ground, and the first and subsequent return strokes. This is an extremely slow-motion animation- the actual process takes only a small fraction of a second. AT RIGHT: Photo of cloud-to-ground lightning.

Fig. 2: From high-speed video of a cloud-to-ground strike near Trenton, Illinois: The stepped leader descends, followed by the bright return stroke in the last 3 frames.

Ground-to-cloud lightning: upward-moving

Unlike cloud-to-ground lightning which starts inside the thunderstorm, a ground-to-cloud lightning flash begins from a tall ground-based object and moves upward. This type of lightning is common with strikes to towers and skyscrapers: read more.

Ground-to-Cloud Lightning animation Ground-to-Cloud Lightning photo

This animation depicts a type of upward-moving ground-to-cloud lightning striking a tall television tower. AT RIGHT: Photo of ground-to-cloud (upward) lightning striking a television broadcast tower.

Watch the video: Does lightning go UP or DOWN?

See more lightning types >

Storm chaser and photographer Dan Robinson
About the Author: Dan Robinson has been a storm chaser, photographer and cameraman for 30 years. His career has involved traveling around the country covering the most extreme weather on the planet including tornadoes, hurricanes, lightning, floods and winter storms. Dan has been extensively published in newspapers, magazines, web articles and more, and has both supplied footage for and appeared in numerous television productions and newscasts. He has also been involved in the research community, providing material for published scientific journal papers on tornadoes and lightning.

See Also:

How Lightning Works
A detailed, step-by-step description of a cloud-to-ground lightning discharge.
Lightning Discharges to TV Towers, Skyscrapers and other Tall Structures
An in-depth look at ground-to-cloud or 'upward moving' lightning discharges to tall structures, including dramatic up-close imagery.

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