![Whirlwind 2250](https://upload.wikimedia.org/wikipedia/commons/2/24/Whirlwind_2250.jpg)
A whirlwind is a weather phenomenon in which a
vortex
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...
of
wind
Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few hou ...
(a vertically oriented rotating column of air) forms due to instabilities and
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
created by heating and
flow
Flow may refer to:
Science and technology
* Fluid flow, the motion of a gas or liquid
* Flow (geomorphology), a type of mass wasting or slope movement in geomorphology
* Flow (mathematics), a group action of the real numbers on a set
* Flow (psych ...
(
current) gradients. Whirlwinds occur all over the world and in any season.
Types
Whirlwinds are subdivided into two main types, the great (or major) whirlwinds, and the lesser (or minor) whirlwinds. The first category includes
tornado
A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...
es,
waterspout
A waterspout is an intense columnar vortex (usually appearing as a funnel cloud, funnel-shaped cloud) that occurs over a body of water. Some are connected to a cumulus congestus cloud, some to a cumuliform cloud and some to a cumulonimbus clou ...
s, and
landspouts. The range of atmospheric vortices constitute a continuum and are difficult to categorize definitively. Some lesser whirlwinds may sometimes form in a similar manner to greater whirlwinds with related increase in intensity. These intermediate types include the
gustnado
A gustnado is a brief, shallow surface-based vortex which forms within the downburst emanating from a thunderstorm. The name is a portmanteau by elision of "gust front tornado", as gustnadoes form due to non-tornadic straight-line wind feature ...
and the
fire whirl
A fire whirl or fire devil (sometimes referred to as a fire tornado) is a whirlwind induced by a fire and often (at least partially) composed of flame or ash. These start with a whirl of wind, often made visible by smoke, and may occur when inte ...
. Other lesser whirlwinds include
dust devil
A dust devil is a strong, well-formed, and relatively short-lived whirlwind. Its size ranges from small (half a metre wide and a few metres tall) to large (more than 10 m wide and more than 1 km tall). The primary vertical motion is u ...
s, as well as
steam devil
A steam devil is a small, weak whirlwind over water (or sometimes wet land) that has drawn fog into the vortex, thus rendering it visible.
They form over large lakes and oceans during cold air outbreaks while the water is still relatively war ...
s,
snow devils, debris devils, leaf devils or hay devils, water devils, and shear
eddies
In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object. Fluid beh ...
such as the mountainado and eddy whirlwinds.
Formation
A major whirlwind (such as a
tornado
A tornado is a violently rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud or, in rare cases, the base of a cumulus cloud. It is often referred to as a twister, whirlwind or cyclone, altho ...
) is formed from
supercell thunderstorm
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...
s (the most powerful type of thunderstorm) or other powerful
storms. When the storms start to spin, they react with other high altitude winds, causing a
funnel to spin. A
cloud
In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may co ...
forms over the funnel, making it visible.
A minor whirlwind is created when local winds start to spin on the ground. This causes a funnel to form. The funnel moves over the ground, pushed by the winds that first formed it. The funnel picks up materials such as
dust
Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...
or
snow
Snow comprises individual ice crystals that grow while suspended in the atmosphere—usually within clouds—and then fall, accumulating on the ground where they undergo further changes.
It consists of frozen crystalline water throughout ...
as it moves over the ground, thus becoming visible.
Duration
Major whirlwinds last longer because they are formed from very powerful winds, and it is hard, though not impossible, to interrupt them. Minor whirlwinds are not as long-lived; the winds that form them do not last long, and when a minor whirlwind encounters an obstruction (a
building
A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and fun ...
, a
house
A house is a single-unit residential building. It may range in complexity from a rudimentary hut to a complex structure of wood, masonry, concrete or other material, outfitted with plumbing, electrical, and heating, ventilation, and air condi ...
, a
tree
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...
, etc.), its rotation is interrupted, as is the windflow into it, causing it to dissipate.
Associated weather
Supercell thunderstorms, other powerful storms, and strong winds are seen with major whirlwinds. Wind storms are commonly seen with minor whirlwinds. Also, small, semi-powerful “wind blasts” may be seen before some minor whirlwinds, which can come from a wind storm. These wind blasts can start to rotate and form minor whirlwinds. Winds from other small storms (such as
rain storms and local
thunderstorm
A thunderstorm, also known as an electrical storm or a lightning storm, is a storm characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere, known as thunder. Relatively weak thunderstorms are someti ...
s) can cause minor whirlwinds to form. Like major whirlwinds, these minor whirlwinds can also be dangerous at times.
Similar phenomena
Eddies
In fluid dynamics, an eddy is the swirling of a fluid and the reverse current created when the fluid is in a turbulent flow regime. The moving fluid creates a space devoid of downstream-flowing fluid on the downstream side of the object. Fluid beh ...
and
vortices
In fluid dynamics, a vortex ( : vortices or vortexes) is a region in a fluid in which the flow revolves around an axis line, which may be straight or curved. Vortices form in stirred fluids, and may be observed in smoke rings, whirlpools in th ...
may form in any
fluid
In physics, a fluid is a liquid, gas, or other material that continuously deforms (''flows'') under an applied shear stress, or external force. They have zero shear modulus, or, in simpler terms, are substances which cannot resist any shear ...
. In water, a
whirlpool is a similar phenomenon.
See also
*
Hurricane
A tropical cyclone is a rapidly rotating storm system characterized by a low-pressure center, a closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms that produce heavy rain and squalls. Depend ...
External links
Fire whirlwind video September 11, 2012 Alice Springs Australia.Severe Storm Definitions & Whirlwind Classification (
TORRO
The Tornado and Storm Research Organisation (TORRO) was founded by Terence Meaden in 1974. Originally called the Tornado Research Organisation it was expanded in 1982 following the inclusion of the Thunderstorm Census Organisation (TCO) after the d ...
)
Whirlwinds(
TORRO
The Tornado and Storm Research Organisation (TORRO) was founded by Terence Meaden in 1974. Originally called the Tornado Research Organisation it was expanded in 1982 following the inclusion of the Thunderstorm Census Organisation (TCO) after the d ...
)
A 'hay devil' from National GeographicA longer version of the above but poorer quality
{{Cyclones
Severe weather and convection
Vortices
Meteorological phenomena