Upper tropospheric cyclonic vortex
Encyclopedia
An upper tropospheric cyclonic vortex is a vortex
, or a circulation with a definable center, that usually moves slowly from east-northeast to west-southwest and is prevalent across Northern Hemisphere
's warm season. Its circulations generally do not extend below 6080 metres (19,947.5 ft) in altitude, as it is an example of a cold-core low
. A weak inverted wave
in the easterlies
is generally found beneath it, and it may also be associated with broad areas of high-level clouds. Downward development results in an increase of cumulus clouds and the appearance of circulation
at ground level. In rare cases, a warm-core cyclone can develop in its associated convective activity, resulting in a tropical cyclone
and a weakening and southwest movement of the nearby upper tropospheric cyclonic vortex. Symbiotic relationships can exist between tropical cyclones and the upper level lows in their wake, with the two systems occasionally leading to their mutual strengthening. When they move over land during the warm season, an increase in monsoon
rain
s occurs.
) to locate the circumpolar trough
s and ridges
, trough lines extend over the eastern and central North Pacific and over the North Atlantic. Case studies of upper tropospheric cyclones in the Atlantic and Pacific have been performed by using airplane reports (wind
s, temperature
s and heights), radiosonde
data, geostationary satellite cloud
imagery, and cloud-tracked winds throughout the troposphere. It was determined they were the origin of an upper tropospheric cold-core lows, or cut-off lows.
relationship. It also means that a pool of cold air aloft is associated with the feature. If both an upper tropospheric cold-core low and lower tropospheric easterly wave
trough are in-phase, with the easterly wave near or to the east of the upper level cyclone
, thunderstorm
development (also known as moist convection) is enhanced. If they are out-of-phase, with the tropical wave west of the upper level circulation, convection
is suppressed due to convergence aloft leading to downward motion over the tropical wave or surface trough in the easterlies. Upper level cyclones also interact with troughs in the subtropical westerlies, such as cold front
s and stationary front
s. When the subtropical disturbances in the Northern Hemisphere actively move southward, or dig, the area between the upper tropospheric anticyclone
to its west and cold-core low
to its east generally have strong northeasterly winds in addition to a rapid development of active thunderstorm activity. Cloud bands associated with upper tropospheric cyclonic vortices are aligned with the vertical wind shear. Animated satellite cloud imagery is a better tool for their early detection and tracking. The low-level convergence caused by the cut-off low can trigger squall line
s and rough seas, and the low-level spiral cloud bands caused by the upper level circulation are parallel to the low-level wind direction. This has also been witnessed with upper level lows which occur at higher latitudes. For example, in areas where small-scale snow bands develop within the cold sector of extratropical cyclone
s.
, the tropical upper tropospheric trough
(TUTT) normally occurs between May and November, with peak activity between July and September. James Sadler suggested a revised model for the TUTT during the early part of the typhoon season in the western Pacific. Both Sadler and Lance Bosart have shown that the tropical upper tropospheric trough cyclonic cells are caused by the mid-latitude disturbance riding around the western side of the tropical upper tropospheric trough
when the subtropical ridge to its south is quite weak. In the north Atlantic, the TUTT is characterized by the semi-permanent circulation pattern that forms in the North Atlantic between August and November. Toby Carlson evaluated data over the eastern Caribbean sea for October 1965 and pinpointed the presence of an upper tropospheric cold-core cyclone. These cold-core cyclones generally form close to the Azores and move south and westward towards a latitude of 20°N. These circulations extend over an area of about 20° of latitude (or 2220 kilometres (1,198.7 nmi)) and 40° of longitude. The lowest level of closed circulation underneath the upper level cold-core cyclone is often between the 700 and the 500-hectopascal level (3000 metres (9,842.5 ft) to 5800 metres (19,028.9 ft) above sea level
). Their life cycles span 5 to 14 days.
The upper tropospheric cyclonic centers in the North Atlantic differ from that in the North Pacific. Most of them are detectable in the low tropospheric temperature field as cold troughs in the easterlies. They tend to vertically tilt toward the northeast. Cumulonimbus clouds and rainfall occur in the southeast quadrant, approximately 5° latitude (or 555 kilometres (299.7 nmi)) from the upper cyclone center. Large variations of cloud cover can exist in different systems. The summer tropical upper tropospheric trough is a dominant feature over the trade wind regions of the North Atlantic Ocean, Gulf of Mexico, and Caribbean Sea, and that the lower tropospheric responses to the tropical upper tropospheric trough in the North Atlantic are differ from those in the North Pacific.
lies over the trade wind
region of the east central Pacific and can cause tropical cyclogenesis
offshore Central America
. University of Hawaii
Professor James C. Sadler
has documented tropical cyclones over the eastern North Pacific that were revealed by weather satellite
observations, and suggested that the upper-tropospheric circulation is a factor in the development, as well as the life history, of the tropical cyclones. Ralph Huschke and Gary Atkinson proposed that a moist southwest wind that results from southeast trades of the eastern South Pacific deflecting towards the Pacific coasts of Central America between June and November, is known as the "temporale". Temporales are most frequent in July and August, when they can reach gale force and cause rough seas/swell. The area of heavy rain is generally located in the northeast quadrant approximately 5° of latitude (or 555 kilometres (299.7 nmi)) from the eye. In the western Pacific, tropical upper tropospheric lows are the main cause for the few tropical cyclones which develop north of the 20th parallel north
and east of the 160th meridian east
during La Nina events.
Trailing upper cyclones and upper troughs can cause additional outflow channels and aid in the intensification process of tropical cyclones. Developing tropical disturbances can help create or deepen upper troughs or upper lows in their wake due to the outflow jet stream
emanating from the developing tropical disturbance/cyclone. In the western North Pacific, there are strong reciprocal relationships between the areas of formative tropical cyclones and that of the lower tropospheric monsoon troughs and the tropical upper tropospheric trough
. Tropical cyclone movement can also be influenced by TUTT cells within 1700 kilometres (917.9 nmi) of their position, which can lead to non-climatological tropical cyclone tracks.
rains during the wet season
.
Vortex
A vortex is a spinning, often turbulent,flow of fluid. Any spiral motion with closed streamlines is vortex flow. The motion of the fluid swirling rapidly around a center is called a vortex...
, or a circulation with a definable center, that usually moves slowly from east-northeast to west-southwest and is prevalent across Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
's warm season. Its circulations generally do not extend below 6080 metres (19,947.5 ft) in altitude, as it is an example of a cold-core low
Cold-core low
A cold-core low, also known as a cold low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere. It is a low pressure system which strengthens with height in accordance with the thermal wind relationship. These...
. A weak inverted wave
Wave
In physics, a wave is a disturbance that travels through space and time, accompanied by the transfer of energy.Waves travel and the wave motion transfers energy from one point to another, often with no permanent displacement of the particles of the medium—that is, with little or no associated mass...
in the easterlies
Easterlies
The easterlies commonly refer to the low latitude trade winds near the equator . These winds carry tropical waves and cyclones from east to west in lower latitudes...
is generally found beneath it, and it may also be associated with broad areas of high-level clouds. Downward development results in an increase of cumulus clouds and the appearance of circulation
Atmospheric circulation
Atmospheric circulation is the large-scale movement of air, and the means by which thermal energy is distributed on the surface of the Earth....
at ground level. In rare cases, a warm-core cyclone can develop in its associated convective activity, resulting in a tropical cyclone
Tropical cyclone
A tropical cyclone is a storm system characterized by a large low-pressure center and numerous thunderstorms that produce strong winds and heavy rain. Tropical cyclones strengthen when water evaporated from the ocean is released as the saturated air rises, resulting in condensation of water vapor...
and a weakening and southwest movement of the nearby upper tropospheric cyclonic vortex. Symbiotic relationships can exist between tropical cyclones and the upper level lows in their wake, with the two systems occasionally leading to their mutual strengthening. When they move over land during the warm season, an increase in monsoon
Monsoon
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
rain
Rain
Rain is liquid precipitation, as opposed to non-liquid kinds of precipitation such as snow, hail and sleet. Rain requires the presence of a thick layer of the atmosphere to have temperatures above the melting point of water near and above the Earth's surface...
s occurs.
History of research
Using charts of mean 200-hectopascal circulation for July through August (located 9200 metres (30,183.7 ft) above sea levelSea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
) to locate the circumpolar trough
Trough (meteorology)
A trough is an elongated region of relatively low atmospheric pressure, often associated with fronts.Unlike fronts, there is not a universal symbol for a trough on a weather chart. The weather charts in some countries or regions mark troughs by a line. In the United States, a trough may be marked...
s and ridges
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
, trough lines extend over the eastern and central North Pacific and over the North Atlantic. Case studies of upper tropospheric cyclones in the Atlantic and Pacific have been performed by using airplane reports (wind
Wind
Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...
s, temperature
Temperature
Temperature is a physical property of matter that quantitatively expresses the common notions of hot and cold. Objects of low temperature are cold, while various degrees of higher temperatures are referred to as warm or hot...
s and heights), radiosonde
Radiosonde
A radiosonde is a unit for use in weather balloons that measures various atmospheric parameters and transmits them to a fixed receiver. Radiosondes may operate at a radio frequency of 403 MHz or 1680 MHz and both types may be adjusted slightly higher or lower as required...
data, geostationary satellite cloud
Cloud
A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...
imagery, and cloud-tracked winds throughout the troposphere. It was determined they were the origin of an upper tropospheric cold-core lows, or cut-off lows.
Characteristics
The tropical upper tropospheric cyclone has a cold core, meaning it is stronger aloft than at the Earth's surface, or stronger in areas of the troposphere with lower pressures. This is explained by the thermal windThermal wind
The thermal wind is a vertical shear in the geostrophic wind caused by a horizontal temperature gradient. Its name is a misnomer, because the thermal wind is not actually a wind, but rather a wind shear.- Physical Intuition :...
relationship. It also means that a pool of cold air aloft is associated with the feature. If both an upper tropospheric cold-core low and lower tropospheric easterly wave
Tropical wave
Tropical waves, easterly waves, or tropical easterly waves, also known as African easterly waves in the Atlantic region, are a type of atmospheric trough, an elongated area of relatively low air pressure, oriented north to south, which move from east to west across the tropics causing areas of...
trough are in-phase, with the easterly wave near or to the east of the upper level cyclone
Cyclone
In meteorology, a cyclone is an area of closed, circular fluid motion rotating in the same direction as the Earth. This is usually characterized by inward spiraling winds that rotate anticlockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere of the Earth. Most large-scale...
, thunderstorm
Thunderstorm
A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...
development (also known as moist convection) is enhanced. If they are out-of-phase, with the tropical wave west of the upper level circulation, convection
Convection
Convection is the movement of molecules within fluids and rheids. It cannot take place in solids, since neither bulk current flows nor significant diffusion can take place in solids....
is suppressed due to convergence aloft leading to downward motion over the tropical wave or surface trough in the easterlies. Upper level cyclones also interact with troughs in the subtropical westerlies, such as cold front
Cold front
A cold front is defined as the leading edge of a cooler mass of air, replacing a warmer mass of air.-Development of cold front:The cooler and denser air wedges under the less-dense warmer air, lifting it...
s and stationary front
Stationary front
A stationary front is a boundary between two different air masses, neither of which is strong enough to replace the other. On a weather map, this is shown by an inter-playing series of blue spikes pointing one direction and red domes pointing the other. They tend to remain essentially in the same...
s. When the subtropical disturbances in the Northern Hemisphere actively move southward, or dig, the area between the upper tropospheric anticyclone
Anticyclone
An anticyclone is a weather phenomenon defined by the United States' National Weather Service's glossary as "[a] large-scale circulation of winds around a central region of high atmospheric pressure, clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere"...
to its west and cold-core low
Cold-core low
A cold-core low, also known as a cold low or cold-core cyclone, is a cyclone aloft which has an associated cold pool of air residing at high altitude within the Earth's troposphere. It is a low pressure system which strengthens with height in accordance with the thermal wind relationship. These...
to its east generally have strong northeasterly winds in addition to a rapid development of active thunderstorm activity. Cloud bands associated with upper tropospheric cyclonic vortices are aligned with the vertical wind shear. Animated satellite cloud imagery is a better tool for their early detection and tracking. The low-level convergence caused by the cut-off low can trigger squall line
Squall line
A squall line is a line of severe thunderstorms that can form along or ahead of a cold front. In the early 20th century, the term was used as a synonym for cold front. It contains heavy precipitation, hail, frequent lightning, strong straight-line winds, and possibly tornadoes and waterspouts....
s and rough seas, and the low-level spiral cloud bands caused by the upper level circulation are parallel to the low-level wind direction. This has also been witnessed with upper level lows which occur at higher latitudes. For example, in areas where small-scale snow bands develop within the cold sector of extratropical cyclone
Extratropical cyclone
Extratropical cyclones, sometimes called mid-latitude cyclones or wave cyclones, are a group of cyclones defined as synoptic scale low pressure weather systems that occur in the middle latitudes of the Earth having neither tropical nor polar characteristics, and are connected with fronts and...
s.
Climatology
In the Northern HemisphereNorthern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
, the tropical upper tropospheric trough
Tropical Upper Tropospheric Trough
A tropical upper tropospheric trough , also known as the mid-oceanic trough, is a trough situated in upper-level tropics. Its formation is usually caused by the intrusion of energy and wind from the mid-latitudes into the tropics. It can also develop from the inverted trough adjacent to an upper...
(TUTT) normally occurs between May and November, with peak activity between July and September. James Sadler suggested a revised model for the TUTT during the early part of the typhoon season in the western Pacific. Both Sadler and Lance Bosart have shown that the tropical upper tropospheric trough cyclonic cells are caused by the mid-latitude disturbance riding around the western side of the tropical upper tropospheric trough
Tropical Upper Tropospheric Trough
A tropical upper tropospheric trough , also known as the mid-oceanic trough, is a trough situated in upper-level tropics. Its formation is usually caused by the intrusion of energy and wind from the mid-latitudes into the tropics. It can also develop from the inverted trough adjacent to an upper...
when the subtropical ridge to its south is quite weak. In the north Atlantic, the TUTT is characterized by the semi-permanent circulation pattern that forms in the North Atlantic between August and November. Toby Carlson evaluated data over the eastern Caribbean sea for October 1965 and pinpointed the presence of an upper tropospheric cold-core cyclone. These cold-core cyclones generally form close to the Azores and move south and westward towards a latitude of 20°N. These circulations extend over an area of about 20° of latitude (or 2220 kilometres (1,198.7 nmi)) and 40° of longitude. The lowest level of closed circulation underneath the upper level cold-core cyclone is often between the 700 and the 500-hectopascal level (3000 metres (9,842.5 ft) to 5800 metres (19,028.9 ft) above sea level
Sea level
Mean sea level is a measure of the average height of the ocean's surface ; used as a standard in reckoning land elevation...
). Their life cycles span 5 to 14 days.
The upper tropospheric cyclonic centers in the North Atlantic differ from that in the North Pacific. Most of them are detectable in the low tropospheric temperature field as cold troughs in the easterlies. They tend to vertically tilt toward the northeast. Cumulonimbus clouds and rainfall occur in the southeast quadrant, approximately 5° latitude (or 555 kilometres (299.7 nmi)) from the upper cyclone center. Large variations of cloud cover can exist in different systems. The summer tropical upper tropospheric trough is a dominant feature over the trade wind regions of the North Atlantic Ocean, Gulf of Mexico, and Caribbean Sea, and that the lower tropospheric responses to the tropical upper tropospheric trough in the North Atlantic are differ from those in the North Pacific.
Interaction with tropical cyclones
The summer TUTT in the Southern HemisphereSouthern Hemisphere
The Southern Hemisphere is the part of Earth that lies south of the equator. The word hemisphere literally means 'half ball' or "half sphere"...
lies over the trade wind
Trade wind
The trade winds are the prevailing pattern of easterly surface winds found in the tropics, within the lower portion of the Earth's atmosphere, in the lower section of the troposphere near the Earth's equator...
region of the east central Pacific and can cause tropical cyclogenesis
Tropical cyclogenesis
Tropical cyclogenesis is the term that describes the development and strengthening of a tropical cyclone in the atmosphere. The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which mid-latitude cyclogenesis occurs...
offshore Central America
Central America
Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. When considered part of the unified continental model, it is considered a subcontinent...
. University of Hawaii
University of Hawaii
The University of Hawaii System, formally the University of Hawaii and popularly known as UH, is a public, co-educational college and university system that confers associate, bachelor, master, and doctoral degrees through three university campuses, seven community college campuses, an employment...
Professor James C. Sadler
James C. Sadler
James C. Sadler was an American meteorologist, and a Professor in Tropical Meteorology at the University of Hawaii where he taught for 22 years. He is considered one of the pioneers of tropical meteorological study.- Career :...
has documented tropical cyclones over the eastern North Pacific that were revealed by weather satellite
Weather satellite
The weather satellite is a type of satellite that is primarily used to monitor the weather and climate of the Earth. Satellites can be either polar orbiting, seeing the same swath of the Earth every 12 hours, or geostationary, hovering over the same spot on Earth by orbiting over the equator while...
observations, and suggested that the upper-tropospheric circulation is a factor in the development, as well as the life history, of the tropical cyclones. Ralph Huschke and Gary Atkinson proposed that a moist southwest wind that results from southeast trades of the eastern South Pacific deflecting towards the Pacific coasts of Central America between June and November, is known as the "temporale". Temporales are most frequent in July and August, when they can reach gale force and cause rough seas/swell. The area of heavy rain is generally located in the northeast quadrant approximately 5° of latitude (or 555 kilometres (299.7 nmi)) from the eye. In the western Pacific, tropical upper tropospheric lows are the main cause for the few tropical cyclones which develop north of the 20th parallel north
20th parallel north
The 20th parallel north is a circle of latitude that is 20 degrees north of the Earth's equatorial plane. It crosses Africa, Asia, the Indian Ocean, the Pacific Ocean, North America, the Caribbean and the Atlantic Ocean....
and east of the 160th meridian east
160th meridian east
The meridian 160° east of Greenwich is a line of longitude that extends from the North Pole across the Arctic Ocean, Asia, the Pacific Ocean, the Southern Ocean, and Antarctica to the South Pole....
during La Nina events.
Trailing upper cyclones and upper troughs can cause additional outflow channels and aid in the intensification process of tropical cyclones. Developing tropical disturbances can help create or deepen upper troughs or upper lows in their wake due to the outflow jet stream
Jet stream
Jet streams are fast flowing, narrow air currents found in the atmospheres of some planets, including Earth. The main jet streams are located near the tropopause, the transition between the troposphere and the stratosphere . The major jet streams on Earth are westerly winds...
emanating from the developing tropical disturbance/cyclone. In the western North Pacific, there are strong reciprocal relationships between the areas of formative tropical cyclones and that of the lower tropospheric monsoon troughs and the tropical upper tropospheric trough
Tropical Upper Tropospheric Trough
A tropical upper tropospheric trough , also known as the mid-oceanic trough, is a trough situated in upper-level tropics. Its formation is usually caused by the intrusion of energy and wind from the mid-latitudes into the tropics. It can also develop from the inverted trough adjacent to an upper...
. Tropical cyclone movement can also be influenced by TUTT cells within 1700 kilometres (917.9 nmi) of their position, which can lead to non-climatological tropical cyclone tracks.
Interaction with monsoon regimes
As upper level lows retrograde over land masses, they can enhance thunderstorm activity during the afternoon. This magnifies regional monsoon regimes, such as that over western North America near the United States and Mexican border, which can be used to effectively forecast monsoon surges in precipitation magnitude. Across the north Indian ocean, the formation of this type of vortex leads to the onset of monsoonMonsoon
Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...
rains during the wet season
Wet season
The the wet season, or rainy season, is the time of year, covering one or more months, when most of the average annual rainfall in a region occurs. The term green season is also sometimes used as a euphemism by tourist authorities. Areas with wet seasons are dispersed across portions of the...
.