Cloud to ground lightning strikes south-west of Wagga Wagga

A dry thunderstorm is a

thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...

that produces thunder and lightning, but where all or most of its precipitation evaporates before reaching the ground. Dry lightning refers to lightning strikes occurring in this situation. Both are so common in the

American West The Western United States (also called the American West, the Western States, the Far West, the Western territories, and the West) is census regions United States Census Bureau As American settlement in the U.S. expanded westward, the mea ...

that they are sometimes used interchangeably. Dry thunderstorms occur essentially in dry conditions, and their lightning is a major cause of wildfires. Because of that, the United States

National Weather Service The National Weather Service (NWS) is an Government agency, agency of the Federal government of the United States, United States federal government that is tasked with providing weather forecasts, warnings of hazardous weather, and other weathe ...

, and other agencies around the world, issue forecasts for its likelihood over large areas.

Where dry thunderstorms occur

Dry thunderstorms generally occur in

deserts A desert is a landscape where little precipitation occurs and, consequently, living conditions create unique biomes and ecosystems. The lack of vegetation exposes the unprotected surface of the ground to denudation. About one-third of the l ...

or places where the lower layers of the atmosphere usually contain little

water vapor Water vapor, water vapour, or aqueous vapor is the gaseous phase of Properties of water, water. It is one Phase (matter), state of water within the hydrosphere. Water vapor can be produced from the evaporation or boiling of liquid water or from th ...

. Any precipitation that falls from elevated thunderstorms can be entirely evaporated as it falls through the lower dry layers. They are common during the summer months across much of western North America and other arid areas. The shaft of precipitation that can be seen falling from a cloud without reaching the ground is called " virga". A thunderstorm does not have to be completely dry to be considered dry; in many areas is the threshold between a "wet" and "dry" thunderstorm.

Hazards

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

Dust storms

Strong winds often develop around dry thunderstorms as the evaporating precipitation causes excessive cooling of the air beneath the storm, which increases its density and thereby its weight relative to the surrounding air. This cool air then descends rapidly and fans out upon impacting the ground, an event often described as a dry microburst. As the gusty winds expand outward from the storm, dry soil and sand are often picked up by the strong winds, creating dust and sand storms known as

haboob A haboob () is a type of intense dust storm carried by the wind of a weather front or thunderstorm. Haboobs occur regularly in arid, dry land area regions throughout the world, including off-Earth, and can be dangerous. Formation and charac ...

Fires

2011-08-04 20 00 00 Susie Fire in the Adobe Range west of Elko Nevada

In areas where trees or other vegetation are present, there is little to no rain that can prevent the lightning from causing them to catch fire. Storm winds also fan the

fire Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products. Flames, the most visible portion of the fire, are produced in the combustion re ...

and

firestorm A firestorm is a conflagration which attains such intensity that it creates and sustains its own wind system. It is most commonly a natural phenomenon, created during some of the largest bushfires and wildfires. Although the term has been used ...

, causing it to spread more quickly. Pyrocumulonimbus are cumuliform clouds that can form over a large fire and that are particularly dry. When the higher levels of the atmosphere are cooler, and the surface is thus warmed to extreme temperatures due to a wildfire, volcano, or other event, convection will occur, and produce clouds and lightning. They are similar to any cumulus cloud but ingest extra

particulates Particulate matter (PM) or particulates are microscopic particles of solid or liquid matter suspension (chemistry), suspended in the atmosphere of Earth, air. An ''aerosol'' is a mixture of particulates and air, as opposed to the particulate ...

from the fire. This increases the voltage difference between the base and the top of the cloud, helping to produce lightning.

Climate change

Climate change is expected to alter patterns of lightning-ignited wildfires. A key factor in the ignition of these wildfires is the type of lightning, with long-continuing-current (LCC) lightning being particularly significant. The risk of lightning-ignited wildfires is influenced not only by the occurrence of LCC lightning but also by the availability of dry fuel, which is influenced by how much rain has fallen before. Scientists predict, some places will see more LCC lightning and less rain, making it easier for wildfires to start. Areas like Southeastern Asia, South America, Africa, and Australia, along with parts of North America and Europe, could be at higher risk for these lightning-caused wildfires.

References

{{Reflist Lightning Light sources

Thunderstorm A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustics, acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorm ...