Dry lightning

Dry lightning is a term which is used to refer to lightning strikes occurring without significant precipitation. The term is a technical misnomer since lightning itself is neither wet nor dry, and also because the thunderstorms which sometimes cause it actually do produce precipitation, although the precipitation does not reach the ground in significant amounts.

Causes

Dry thunderstorms

Main article: Dry thunderstorm
A lightning-sparked wildfire in Nevada.

Such thunderstorms are most common in the western portion of the United States during the summer. They occur when the rain produced by thunderstorms falls through a substantial layer of very dry air which evaporates the precipitation before it reaches the ground. For fire weather purposes, a thunderstorm does not have to be completely dry to be considered dry; in many areas, a tenth of an inch of rain is the threshold between a "wet" and "dry" thunderstorm.[1]

Dry thunderstorms are notable for two other reasons: they are the most common natural origin of wildland fires, and they can produce strong gusty surface winds that can fan flames.

Pyrocumulus clouds

Main article: Pyrocumulus cloud

Clouds do not have to be formed of water droplets to produce electricity. Pyrocumulus clouds produce lightning for the same reason that it is produced by cumulonimbus clouds. When the higher levels of the atmosphere are cooler, and the surface is warmed to extreme temperatures due to a wildfire, volcano, etc., convection will occur, and the convection produces lightning.

See also

References

  1. ↑ http://www.srh.noaa.gov/abq/?n=clifeature2010drythunderstorms NWS Albuquerque: Fire Weather Topics - Dry Thunderstorms