A shelf cloud associated with a heavy or severe thunderstorm over Enschede, Netherlands

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 (a wind storm), 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).

Formation

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.

Types

Sea storm, west coast of Portugal

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 mm or 1/4" of accumulation is all that is required, especially in combination with breezy conditions, to start downing power lines as well as tree limbs.^[1] 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 (winds of around 35 kts/40 mph or greater), heavy snow (accumulating at a rate of a 5+ cm/2+ in per hour), and very cold conditions (below approximately -10C/14F). As of late, the temperature criteria has fallen out of the definition across the United States^[2]
• Snowstorm - A heavy fall of snow (accumulating at a rate of a 5+ cm/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.^[3]
• Ocean Storm - Storm conditions out at sea are defined as having sustained winds of 48 kts/55 mph or greater.^[4] Usually just referred to as a storm, these systems can sink vessels of all types and sizes out at sea.
• 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 or greater sustained for at least one minute.
• Gale - An extratropical storm with sustained winds between 34-48 kts/39-55 mph.^[4]
• 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 their origin in the tropics and their cyclonic nature. They 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.

Heavy storm brought by Typhoon Sanvu in Hong Kong. Sanvu was the first typhoon in 2005 that passed through the city.

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.^[5]

Tropical cyclones can produce extremely high winds, tornadoes, torrential rain (leading to mudslides and flash floods), and drive storm surge onto coastal areas. Though the effects on populations and ships can be catastrophic, tropical cyclones have been known to relieve drought conditions. They carry heat away from the tropics, an important mechanism of the global atmospheric circulation that maintains equilibrium in the environment.

• Hailstorm - a type of storm that precipitates chunks of ice that aren't snow. 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 baseball and golf ball sized hail 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 American Midwest is the most prone area, especially Oklahoma and Kansas.

Classification

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.^[6] 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.

Extraterrestrial storms

The Great Red Spot on Jupiter

Storms are not unique to Earth; other heavenly 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 has its own lesser known Great Dark Spot.

In September of 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 (ca. 7,900 miles). The storm was observed earlier in September, 1990 and acquired the name Dragon Storm.

Art and culture

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. This near-catastrophe provided the inspiration and background for William Shakespeare's play, The Tempest.^[7]

The ninth wave is a painting by Ivan Aivazovsky.

British painter and printmaker J. M. W. Turner (1775-1851) created some of the most lasting and famous impressions of the sublime and stormy seas. His 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. Perhaps the best example and the most famous of Turner’s dramatic seascapes is The Slave Ship (properly Slavers throwing overboard the Dead and Dying - Typhoon Coming On) of 1840.

Russian bard Vladimir Vysotskiy has been singing the song the title of which could be roughly translated as "We say not 'storms', but 'stormes'" (Russian: "Мы говорим не 'штормы', а 'шторма'").

In Greek mythology there were several gods of storms: Briareos, by himself the god of sea storms, Aigaios, a god of the violent sea storms and Aiolos who kept the storm-winds, squalls and tempests locked away in the hollows of the floating island of Aiolia, to be released at the command of the gods.

According to the Bible, a giant storm sent by God flooded the Earth. See Noah's Ark.

See also

• Atmospheric pressure
• Blizzard
• Cyclone
• Derecho
• Extreme weather, a list of historical storms and other extreme weather
• Freezing rain
• Geomagnetic storm
• National Oceanic and Atmospheric Administration
• Low pressure area
• Storm chasing
• Storm warning
• Tornado
• Tropical cyclone

References

External links

Look up storm in Wiktionary, the free dictionary.

Wikiquote has a collection of quotations related to:

Storm

• Branick, Michael. NOAA Technical Memorandum NWS SR-145: A comprehensive glossary of weather terms for storm spotters. Second edition. 1996.