A storm is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather. It may be marked by strong wind, thunder and lightning (a thunderstorm), heavy precipitation, such as ice (ice storm), or wind transporting some substance through the atmosphere (as in a dust storm, snowstorm, hailstorm, etc).
Storms are created when a center of low pressure develops, with a system of high pressure surrounding it.
This combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. Small, localized areas of low pressure can form from hot air rising off hot ground, resulting in smaller disturbances such as dust devils and whirlwinds.
There are many varieties and names for storms.
- Ice Storm - Ice storms are one of the most dangerous forms of winter weather. When surface temperatures are below freezing, but a thick layer of above freezing air remains aloft above ground level, rain can fall into the freezing layer and freeze upon impact into a "glaze". In general, 8 millimeters (1/4 in) of accumulation is all that is required, especially in combination with breezy conditions, to start downing power lines as well as tree limbs. Ice storms also make unheated road surfaces too slick to drive upon. Ice storms can vary in time range from hours to days and can cripple both small towns and large urban centers alike.
- Blizzard - There are varying definitions for blizzards, both over time and by location. In general, a blizzard is accompanied by gale-force winds, heavy snow (accumulating at a rate of at least 5 centimeters (2 in) per hour), and very cold conditions (below approximately -10 degrees Celsius or 14 F). As of late, the temperature criteria has fallen out of the definition across the United States
- Snowstorm - A heavy fall of snow accumulating at a rate of more than 5 centimeters (2 in) per hour that lasts several hours. Snow storms, especially ones with a high liquid equivalent and breezy conditions, can down tree limbs, cut off power, and paralyze travel over a large region.
- Ocean Storm - Storm conditions out at sea are defined as having sustained winds of 48 knots (55 mph or 90 km/h) or greater. Usually just referred to as a storm, these systems can sink vessels of all types and sizes.
- Firestorm - Firestorms are conflagrations which attain such intensity that they create and sustain their own wind systems. It is most commonly a natural phenomenon, created during some of the largest bushfires, forest fires, and wildfires. The Peshtigo Fire is one example of a firestorm. Firestorms can also be deliberate effects of targeted explosives such as occurred as a result of the aerial bombings of Dresden and Tokyo during World War II. Nuclear detonations almost invariably generate firestorms
- Dust devil - a small, localized updraft of rising air.
- Windstorm - a severe weather condition indicated by high winds and with little or no rain, like European windstorm.
- Squall - sudden onset of wind increase of at least 16 knots (30 km/h) or greater sustained for at least one minute.
- Gale - An extratropical storm with sustained winds between 34-48 knots (39-55 mph or 63-90 km/h).
- Thunderstorm - A thunderstorm is a type of storm that generates lightning and the attendant thunder. It is normally accompanied by heavy precipitation. Thunderstorms occur throughout the world, with the highest frequency in tropical rainforest regions where there are conditions of high humidity and temperature along with atmospheric instability. These storms occur when high levels of condensation form in a volume of unstable air that generates deep, rapid, upward motion in the atmosphere. The heat energy creates powerful rising air currents that swirl upwards to the tropopause. Cool descending air currents produce strong downdraughts below the storm. After the storm has spent its energy, the rising currents die away and downdraughts break up the cloud. Individual storm clouds can measure 2-10 km across.
- Tropical Cyclone - A tropical cyclone is a storm system with a closed circulation around a centre of low pressure, fueled by the heat released when moist air rises and condenses. The name underscores its origin in the tropics and their cyclonic nature. Tropical cyclones are distinguished from other cyclonic storms such as nor'easters and polar lows by the heat mechanism that fuels them, which makes them "warm core" storm systems.
- Tropical cyclones form in the oceans if the conditions in the area are favorable, and depending on their strength and location, there are various terms by which they are called, such as tropical depression, tropical storm, hurricane and typhoon.
- Hailstorm - a type of storm that precipitates chunks of ice. Hailstorms usually occur during regular thunder storms. While most of the hail that precipitates from the clouds is fairly small and virtually harmless, there have been cases of hail greater than 2 inches diameter that caused much damage and injuries.
- Tornado - A tornado is a violent, destructive wind storm occurring on land. Usually its appearance is that of a dark, funnel-shaped cyclone. Often tornadoes are preceded by a thunderstorm and a wall cloud. They are often called the most destructive of storms, and while they form all over the world, the interior of the United States the most prone area, especially throughout Tornado Alley.
A strict meteorological definition of a terrestrial storm is a wind measuring 10 or higher on the Beaufort scale, meaning a wind speed of 24.5 m/s (89 km/h, 55 mph) or more; however, popular usage is not so restrictive. Storms can last anywhere from 12 to 200 hours, depending on season and geography. The east and northeast storms are noted for the most frequent repeatability and duration, especially during the cold period. Big terrestrial storms alter the oceanographic conditions that in turn may affect food abundance and distribution: strong currents, strong tides, increased siltation, change in water temperatures, overturn in the water column, etc.
Storms are not unique to Earth; other planetary bodies with a sufficient atmosphere (gas giants in particular) also undergo stormy weather. A famous example is the Great Red Spot on Jupiter. Though technically a hurricane, it is larger than the earth and has been raging for at least 340 years, when it was observed by astronomer Galileo Galilei. Neptune also had its own lesser known Great Dark Spot.
In September 1994 Hubble telescope using Wide Field Planetary Camera 2 imaged the storms on Saturn, generated by upwelling of warmer air, similar to a terrestrial thunderhead. The east-west extent of the same-year storm was equal to the diameter of Earth. The storm was observed earlier in September 1990 and acquired the name Dragon Storm.
Notable storms in art and culture
According to the Bible, a giant storm sent by God flooded the Earth. Noah and his family and the animals entered the Ark, and "the same day were all the fountains of the great deep broken up, and the windows of heaven were opened, and the rain was upon the earth forty days and forty nights." The flood covered even the highest mountains to a depth of more than twenty feet, and all creatures died; only Noah and those with him on the Ark were left alive.
In Greek mythology there were several gods of storms: Briareos, the god of sea storms; Aigaios, a god of the violent sea storms; and Aiolos, keeper of storm-winds, squalls and tempests.
William Shakespeare's play The Tempest (1611) was based on the following incident. Sir Thomas Gates, future governor of Virginia, was on his way to England from Jamestown, Virginia. On Saint James Day while between Cuba and the Bahamas a hurricane raged for nearly two days. Though one of the small vessels in the fleet sank to the bottom of the Florida Straits, seven of the remaining vessels reached Virginia within several days after the storm. The flagship of the fleet, known as Sea Adventure, disappeared and was presumed lost. A small bit of fortune befell the ship and her crew when they made landfall on Bermuda. The vessel was damaged on a surrounding coral reef, but all aboard survived for nearly a year on the island. The British colonists claimed the island and quickly settled Bermuda. In May 1610, they set forth for Jamestown, this time arriving at their destination.
The Romantic seascape painters J. M. W. Turner and Ivan Aivazovsky created some of the most lasting impressions of the sublime and stormy seas that are firmly imprinted on the popular mind. Turner's representations of powerful natural forces reinvented the traditional seascape during the first half of the nineteenth century. Upon his travels to Holland, he took note of the familiar large rolling waves of the English seashore transforming into the sharper, choppy waves of a Dutch storm. A characteristic example of Turner’s dramatic seascape is The Slave Ship of 1840. Aivazovsky left several thousand turbulent canvases in which he increasingly eliminated human figures and historical background to focus on such essential elements as light, sea, and sky. His grandiose Ninth Wave (1850) is an ode to human daring in the face of the elements.
Storms were also portrayed in several works of music. Examples are Beethoven's Pastoral Symphony (the fourth movement), Presto of the violin concerto RV 315 (Summer) from the Four Seasons by Vivaldi, and a scene in Act II of Rossini's opera The Barber of Seville.
Types of storm with "storm" in name
Types of storm without "storm" in name
Structural devices built for storms
Other storm topics