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Weather Library > Lightning FAQ: 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.

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Cloud-to-ground lightning: downward-moving

For a negative cloud-to-ground discharge (the most common type of lightning striking the ground), the stepped leader (the channel of ionized air) begins in the lower section of a thunderstorm cloud and 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. 1: From high-speed video of a cloud-to-ground strike near Arian, Texas: 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.

See more lightning types >

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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