Cyclone Catarina, a rare South Atlantic tropical cyclone viewed from the International Space Station on March 26, 2004

In meteorology, a cyclone is an area of low atmospheric pressure characterized by inward spiraling winds that rotate counter clockwise in the northern hemisphere and clockwise in the southern hemisphere of the Earth. Cyclone Catarina is one of several informal names for a South Atlantic tropical cyclone that hit southeastern Brazil in late March 2004 A South Atlantic Tropical cyclone is an unusual weather event Events 1026 - Pope John XIX crowns Conrad II as Holy Roman Emperor. "MMIV" redirects here For the Modest Mouse album see " Baron von Bullshit Rides Again " Meteorology (from Greek grc μετέωρος metéōros, "high in the sky" and grc -λογία -logia) is the Interdisciplinary In Mathematics, a spiral is a Curve which emanates from a central point getting progressively farther away as it revolves around the point Wind is the flow of Air or other Gases that compose an Atmosphere (including but not limited to the Earth's) A clockwise motion is one that proceeds 'like the Clock 's hands' from the top to the right then down and then to the left and back to the top Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball' A clockwise motion is one that proceeds 'like the Clock 's hands' from the top to the right then down and then to the left and back to the top Southern Hemisphere is the half of a Planet that is South of the Equator —the word hemisphere literally means 'half ball' ^[1][2] The generic term covers a wide variety of meteorological phenomena. A meteorological phenomenon is a Weather event which can be explained by the principles of Meteorology. These include tropical cyclones and extratropical cyclones, so meteorologists rarely use "cyclone" without additional qualification. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low

Structure

There are a number of structural characteristics common to all cyclones. Their center is the area of lowest atmospheric pressure, often known in mature tropical and subtropical cyclones as the eye. Near the center, the pressure gradient force (from the pressure in the center of the cyclone compared to the pressure outside the cyclone) and the Coriolis force must be in an approximate balance, or the cyclone would collapse on itself as a result of the difference in pressure. In physics the Coriolis effect is an apparent deflection of moving objects when they are viewed from a Rotating frame of reference. The wind flow around a large cyclone is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere as a result of the Coriolis effect. A clockwise motion is one that proceeds 'like the Clock 's hands' from the top to the right then down and then to the left and back to the top (An anticyclone, on the other hand, rotates clockwise in the northern hemisphere, and counterclockwise in the southern hemisphere. In Meteorology, an anticyclone (that is opposite to a Cyclone) is a Weather phenomenon in which there is a descending movement of the air and )

Formation

Radar image of a tropical cyclone in the northern hemisphere. Radar is a system that uses electromagnetic waves to identify the range altitude direction or speed of both moving and fixed objects such as Aircraft, ships A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Northern Hemisphere is the half of a Planet that is North of the Equator —the word hemisphere literally means 'half ball'

Main article: Cyclogenesis

Cold-core cyclones (most cyclone varieties) form due to the nearby presence of an upper level trough, which increases divergence over an area that induces upward motion and surface low pressure. Cyclogenesis is the development or strengthening of cyclonic circulation in the atmosphere (a low pressure area Warm-core cyclones (such as tropical cyclones and many mesocyclones) can have their initial start due to a nearby upper trough, but after formation of the initial disturbance, depend upon a storm-relative upper level high to maintain or increase their strength.

Categorization

Each of the six main types of cyclone has further characteristics which define it as either a Polar cyclone, Polar low, Extratropical, Subtropical, Tropical, or Mesoscale. Polar Cyclones (also known as polar vortices, Arctic cyclones, and sub-polar cyclones) are vast areas of low pressure which strengthen in the A polar low is a small-scale short-lived atmospheric low pressure system (depression that is found over the ocean areas poleward of the main Polar front in Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low A subtropical cyclone is a Weather system that has some characteristics of a Tropical cyclone and some characteristics of an Extratropical cyclone. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding A mesocyclone is a Vortex of air approximately 2 to 10 km in diameter (the Mesoscale of meteorology within a convective Storm

Polar cyclone

Main article: Polar cyclone

Polar or Arctic cyclones are vast areas of low pressure. Polar Cyclones (also known as polar vortices, Arctic cyclones, and sub-polar cyclones) are vast areas of low pressure which strengthen in the A polar cyclone is a low pressure weather system, usually spanning 1,000–2,000 kilometers, in which the air circulates in a counterclockwise direction in the northern hemisphere, and a clockwise direction in the southern. The weather is a set of all the phenomena occurring in a given Atmosphere at a given Time.

Polar low

Polar low over the Barents Sea on February 27, 1987

Main article: Polar low

A polar low is a small-scale, short-lived atmospheric low pressure system (depression) that is found over the ocean areas poleward of the main polar front in both the Northern and Southern Hemispheres. The Barents Sea (Barentshavet Баренцево море is a part of the Arctic Ocean located north of Norway and Russia. Events 1560 - The Treaty of Berwick, which would expel the French from Scotland, is signed by England and the Congregation Year 1987 ( MCMLXXXVII) was a Common year starting on Thursday (link displays 1987 Gregorian calendar) A polar low is a small-scale short-lived atmospheric low pressure system (depression that is found over the ocean areas poleward of the main Polar front in A low pressure area, or " low " is a region where the Atmospheric pressure is lower in relation to the surrounding area In Meteorology, the polar front is the boundary between the polar cell and the Ferrel cell in each hemisphere The systems usually have a horizontal length scale of less than 1,000 km and exist for no more than a couple of days. They are part of the larger class of mesoscale weather systems. Mesoscale Meteorology is the study of Weather systems smaller than Synoptic scale systems but larger than microscale and Storm-scale cumulus Polar lows can be difficult to detect using conventional weather reports and are a hazard to high-latitude operations, such as shipping and gas and oil platforms.

Polar lows have been referred to by many other terms, such as polar mesoscale vortex, Arctic hurricane, Arctic low, and cold air depression. Today the term is usually reserved for the more vigorous systems that have near-surface winds of at least 17 m/s.

Extratropical

A fictitious synoptic chart of an extratropical cyclone affecting the UK and Ireland. The blue arrows between isobars indicate the direction of the wind, while the "L" symbol denotes the centre of the "low". Note the occluded, cold and warm frontal boundaries. A surface weather analysis is a special type of Weather map that provides a view of Weather elements over a geographical area at a specified time based on information

Main article: Extratropical cyclone

An extratropical cyclone, sometimes inaccurately called a cyclone, is a synoptic scale low pressure weather system that has neither tropical nor polar characteristics, being connected with fronts and horizontal gradients in temperature and dew point otherwise known as "baroclinic zones". Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low The synoptic scale in Meteorology (also known as large scale or cyclonic scale) is a horizontal length scale of the order of 1000 kilometres (about 620 A low pressure area, or " low " is a region where the Atmospheric pressure is lower in relation to the surrounding area A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Polar Cyclones (also known as polar vortices, Arctic cyclones, and sub-polar cyclones) are vast areas of low pressure which strengthen in the A surface weather analysis is a special type of Weather map that provides a view of Weather elements over a geographical area at a specified time based on information In Vector calculus, the gradient of a Scalar field is a Vector field which points in the direction of the greatest rate of increase of the scalar Temperature is a physical property of a system that underlies the common notions of hot and cold something that is hotter generally has the greater temperature The dew point (sometimes spelled dewpoint) is the Temperature to which a given parcel of Air must be cooled at constant Barometric pressure, ^[3]

The descriptor "extratropical" refers to the fact that this type of cyclone generally occurs outside of the tropics, in the middle latitudes of the planet. These systems may also be described as "mid-latitude cyclones" due to their area of formation, or "post-tropical cyclones" where extratropical transition has occurred,^[3][4] and are often described as "depressions" or "lows" by weather forecasters and the general public. Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low These are the everyday phenomena which along with anti-cyclones, drive the weather over much of the Earth. In Meteorology, an anticyclone (that is opposite to a Cyclone) is a Weather phenomenon in which there is a descending movement of the air and

Although extratropical cyclones are almost always classified as baroclinic since they form along zones of temperature and dewpoint gradient, they can sometimes become barotropic late in their life cycle when the temperature distribution around the cyclone becomes fairly uniform with radius. In Fluid dynamics, the baroclinity (sometimes called baroclinicity) is a measure of the Stratification in a fluid In Meteorology, a barotropic atmosphere is one in which the pressure depends only on the density and vice versa so that isobaric surfaces (constant pressure surfaces

Subtropical

Main article: Subtropical cyclone

A subtropical cyclone is a weather system that has some characteristics of a tropical cyclone and some characteristics of an extratropical cyclone. A subtropical cyclone is a Weather system that has some characteristics of a Tropical cyclone and some characteristics of an Extratropical cyclone. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of Cyclones defined as synoptic scale low It can form in a wide band of latitude, from the equator to 50°. Latitude, usually denoted symbolically by the Greek letter phi ( Φ) gives the location of a place on Earth (or other planetary body north or south of the The equator (sometimes referred to colloquially as "the Line") is the intersection of the Earth 's surface with the plane perpendicular to the

Tropical

Main article: Tropical cyclone

A tropical cyclone is a storm system fueled by the heat released when moist air rises and the water vapor in it condenses. A tropical cyclone is a storm system characterized by a low pressure center and numerous Thunderstorms that produce strong winds and Flooding Condensation is the change of the physical state of aggregation (or simply state of matter from gaseous phase into liquid phase The term describes the storm's origin in the tropics and its cyclonic nature, which means that its circulation is counterclockwise in the northern hemisphere and clockwise in the southern hemisphere. The Tropics are centered on the Equator and limited in Latitude by the Tropic of Cancer in the northern hemisphere at approximately 23°26' (23 Tropical cyclones are distinguished from other cyclonic windstorms such as nor'easters, European windstorms, and polar lows by the heat mechanism that fuels them, which makes them "warm core" storm systems. A nor'easter (also northeaster; see below is a macro-scale Storm along the East Coast of the United States and Atlantic Canada. A European windstorm is a severe cyclonic storm that tracks across the North Atlantic towards northwestern Europe in the winter months A polar low is a small-scale short-lived atmospheric low pressure system (depression that is found over the ocean areas poleward of the main Polar front in

Depending on their location and strength, there are various terms by which tropical cyclones are known, such as hurricane, typhoon, tropical storm, cyclonic storm and tropical depression.

Tropical cyclones can produce extremely strong winds, tornadoes, torrential rain, high waves, and storm surges. A tornado is a violent rotating column of air which is in contact with both the surface of the earth and a Cumulonimbus cloud or in rare cases the base of a Cumulus Storm surge or tidal surge is an offshore rise of water associated with a low pressure weather system typically a Tropical cyclone. The heavy rains and storm surges can produce extensive flooding. A flood is an overflow of an expanse of water that submerges land a deluge Although their effects on human populations can be devastating, tropical cyclones also can have beneficial effects by relieving drought conditions. A drought is an extended period of months or years when a region notes a deficiency in its water supply They carry heat away from the tropics, an important mechanism of the global atmospheric circulation that maintains equilibrium in the Earth's troposphere. Atmospheric circulation is the large-scale movement of air and the means (together with the smaller Ocean circulation) by which Heat is distributed on the surface The troposphere is the lowest portion of Earth's atmosphere. It contains approximately 75% of the atmosphere's mass and almost all of its Water vapor and

Mesoscale

Main article: Mesocyclone

A mesocyclone is a cyclonic vortex of air, between approximately 2 and 10 km diameter within a convective storm. A mesocyclone is a Vortex of air approximately 2 to 10 km in diameter (the Mesoscale of meteorology within a convective Storm They can often be found in association with updrafts in supercells, where tornadoes may form. A supercell is a severe thunderstorm with a deep continuously rotating updraft (a Mesocyclone) A tornado is a violent rotating column of air which is in contact with both the surface of the earth and a Cumulonimbus cloud or in rare cases the base of a Cumulus The term refers only to mesoscale cyclones found within convective storms, and does not apply to other cyclones on the mesoscale. Mesoscale Meteorology is the study of Weather systems smaller than Synoptic scale systems but larger than microscale and Storm-scale cumulus ^[5] Storms with mesocyclones can feature strong surface winds and severe hail. Hail is a form of precipitation which consists of balls or irregular lumps of ice (hailstones

Extraterrestrial cyclones

Main article: Extraterrestrial cyclone

Cyclone on Mars, imaged by the Hubble Space Telescope

Cyclones are not unique to Earth. Extraterrestrial cyclones are Cyclones found on other Planets Venus Venus has two large long-lived pairs of inverted anticyclones The Hubble Space Telescope ( HST; also known colloquially as "the Hubble" or just "Hubble" is a space telescope that was carried into Cyclonic storms are common on Jovian planets, like the Small Dark Spot on Neptune. A gas giant (sometimes also known as a Jovian planet after the planet Jupiter, or giant planet) is a large Planet that is not primarily The Small Dark Spot, sometimes also called Dark Spot 2 or The Wizard's Eye, was a southern Cyclonic storm on the Planet Neptune. Neptune ( English|AmE] ] is the eighth and farthest Planet from the Sun in the Solar System. Mars has also exhibited cyclonic storms. Jovian storms like the Great Red Spot are usually mistakenly named as giant hurricanes or cyclonic storms. However, this is inaccurate, as the Great Red Spot is, in fact, the inverse phenomenon, an anticyclone. In Meteorology, an anticyclone (that is opposite to a Cyclone) is a Weather phenomenon in which there is a descending movement of the air and ^[6]

See also

• Anticyclone
• Cyclogenesis
• Eye (cyclone)
• Gyre
• List of environment topics
• Meteorology
• Mesocyclone
• Polar cyclone
• Polar low
• Extratropical cyclone
• Subtropical cyclone
• Tropical cyclone
• Tropical cyclogenesis

References

External links

• Fundamental of Physical Geography: The Mid-Latitude Cyclone - Dr. Michael Pidwirny, University of British Columbia, Okanagan
• Glossary Definition: Cyclogenesis - The National Snow and Ice Data Center
• Glossary Definition: Cyclolysis - The National Snow and Ice Data Center
• Weather Facts: The Polar Low - Weather Online UK
• NOAA FAQ
• Cyclones 'ClearlyExplained'
• Kent Cyclone - Listen to 'Cyclone What?' here
• The EM-DAT International Disaster Database by the Centre for Research on the Epidemiology of Disasters
• Task Force Cyclone