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Nearby Lightning Strike (July, 2000) |
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This flash was close enough that the ground contact point is visible. Taken from a point about 20' AGL, looking due south from my home on Robbinsville, NJ, this picture includes a relatively unobstructed view of the lowest portion of the lighting path. The point of contact is estimated to be in a wooded area about 0.5 mile from the camera. |
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| The CG stroke actually emerges from the cloud base about the middle of the picture, just above the silhouette of the tree. A cloud-air (CA) discharge, or perhaps a branch from the CG discharge, proceeds directly towards the camera and only appears to be a section of vertical channel. |
In this close-up, it is clear the channel terminates behind the tree (a Dawn Redwood which now dominates the southern view from this window.) No unattached upward streamers are visible. The relatively low luminousity of the main channel (i.e. the film is not overexposed) indicates a low number of strokes. |
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With average stepped leader lengths of about 50m, the visible segments of this channel indicate the the flash is farther away than the ~20m the tree is from the camera. However, in the close-up view*, the straight sections of the channel show some tortuosity indicating fine structure* on a scale of a few meters. Lightning channel tortuosity has been observed on the cm-scale; see Idone, V. Microscale tortuosity and its variation as observed in triggered lightning channels. J. Geophys. Res. 100 No. D11, 22943-22965 (1995).
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