Tropical cyclogenesis

developmentdevelopeddeveloptropical developmentcyclogenesistropical cyclone formationformationtropical characteristicstropical cyclone developmentformed
Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere.wikipedia
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Tropical cyclone

hurricanetropical stormhurricanes
Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere. A recent example of a tropical cyclone that maintained itself over cooler waters was Epsilon of the 2005 Atlantic hurricane season. Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment.
Tropical cyclones typically form over large bodies of relatively warm water.

Sea surface temperature

sea surface temperatureswater temperaturesocean temperatures
Tropical cyclogenesis requires six main factors: sufficiently warm sea surface temperatures (at least ), atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to develop a low-pressure center, a pre-existing low-level focus or disturbance, and low vertical wind shear.
Warm sea surface temperatures are known to be a cause of tropical cyclogenesis over the Earth's oceans.

Hurricane Epsilon

Epsilon
A recent example of a tropical cyclone that maintained itself over cooler waters was Epsilon of the 2005 Atlantic hurricane season.
The NHC introduced the system in its tropical weather outlook on November 28, with the possibility of subtropical or tropical development noted.

Hurricane Catarina

105 mph (2004)CatarinaCatarina (2004)
Over four tropical cyclones have been observed here such as— a weak tropical storm in 1991 off the coast of Africa near Angola, Hurricane Catarina, which made landfall in Brazil in 2004 at Category 2 strength, and a smaller storm in January 2004, east of Salvador, Brazil.
The combination of the two led to a slow transition from an extratropical cyclone to a subtropical cyclone by March 24. The storm continued to obtain tropical characteristics and became a tropical storm the next day while the winds steadily increased.

Mediterranean tropical-like cyclone

MedicanemedicanesMediterranean Sea
Examples of these "Mediterranean tropical cyclones" formed in September 1947, September 1969, September 1973, August 1976, January 1982, September 1983, December 1984, December 1985, October 1994, January 1995, October 1996, September 1997, December 2005, September 2006, November 2011, November 2014, November 2017 and September 2018.
A majority of Mediterranean tropical cyclones (tropical cyclogenesis) form over two separate regions.

1975 Pacific Northwest hurricane

Unnamed Hurricanean unnamed hurricaneHurricane 12
On rare occasions, such as Alex in 2004, Alberto in 1988, and the 1975 Pacific Northwest hurricane, storms may form or strengthen in this region.
With warm water temperatures, the system strengthened and began to develop tropical characteristics.

Intertropical Convergence Zone

near-equatorial troughITCZIntertropical Convergence Zone (ITCZ)
Whether it be a depression in the intertropical covergence zone (ITCZ), a tropical wave, a broad surface front, or an outflow boundary, a low level feature with sufficient vorticity and convergence is required to begin tropical cyclogenesis.
Tropical cyclogenesis depends upon low-level vorticity as one of its six requirements, and the ITCZ fills this role as it is a zone of wind change and speed, otherwise known as horizontal wind shear.

1988 Atlantic hurricane season

1988Tropical Storm Alberto1988 season
On rare occasions, such as Alex in 2004, Alberto in 1988, and the 1975 Pacific Northwest hurricane, storms may form or strengthen in this region.
On September 2 a cluster of thunderstorms associated with a northwestward-moving tropical wave developed a surface low near Bermuda.

Jet stream

jetstreampolar jet streamsubtropical jet stream
There are cases where large, mid-latitude troughs can help with tropical cyclogenesis when an upper-level jet stream passes to the northwest of the developing system, which will aid divergence aloft and inflow at the surface, spinning up the cyclone.
The subtropical jet stream across the deep tropics of the Northern Hemisphere is enhanced due to increased convection in the equatorial Pacific, which decreases tropical cyclogenesis within the Atlantic tropics below what is normal, and increases tropical cyclone activity across the eastern Pacific.

Outflow boundary

gust frontoutflow boundariesoutflow
Whether it be a depression in the intertropical covergence zone (ITCZ), a tropical wave, a broad surface front, or an outflow boundary, a low level feature with sufficient vorticity and convergence is required to begin tropical cyclogenesis.
Tropical cyclogenesis

Tropical wave

easterly wavetropical wavestropical disturbance
Whether it be a depression in the intertropical covergence zone (ITCZ), a tropical wave, a broad surface front, or an outflow boundary, a low level feature with sufficient vorticity and convergence is required to begin tropical cyclogenesis.
Tropical cyclogenesis

Subtropical Cyclone Katie

Katiea rare subtropical cyclone
But in mid-2015, a rare subtropical cyclone was identified in early May relatively close to Chile.
Tropical cyclone formation in this extreme part of the Southeast Pacific is so rare that no warning agencies have yet been assigned to the region east of 120°W.

Extratropical cyclone

extratropicalextratropical transitionextratropical storm
Typically, tropical cyclones will undergo extratropical transition after recurving polewards, and typically become fully extratropical after reaching 45–50˚ of latitude.
Tropical cyclogenesis

Monsoon trough

monsoon depressionmonsoonmonsoonal trough
Monsoon trough
This is because a pre-existing near-surface disturbance with sufficient spin and convergence is one of the six requirements for tropical cyclogenesis.

Atmosphere

atmosphericatmospheresplanetary atmospheres
Tropical cyclogenesis is the development and strengthening of a tropical cyclone in the atmosphere.

Tropics

tropicaltropictropical zone
The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs.

Temperate climate

temperatetemperate zonetemperate zones
The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs.

Cyclogenesis

bombingCyclogenesis, extratropical cyclonesdeepening
The mechanisms through which tropical cyclogenesis occurs are distinctly different from those through which temperate cyclogenesis occurs.

Convection

convectiveconvection currentsconvection current
Tropical cyclogenesis involves the development of a warm-core cyclone, due to significant convection in a favorable atmospheric environment.

Humidity

humidspecific humidityair humidity
Tropical cyclogenesis requires six main factors: sufficiently warm sea surface temperatures (at least ), atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to develop a low-pressure center, a pre-existing low-level focus or disturbance, and low vertical wind shear.

Troposphere

troposphericdivergencemid-tropospheric
Tropical cyclogenesis requires six main factors: sufficiently warm sea surface temperatures (at least ), atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to develop a low-pressure center, a pre-existing low-level focus or disturbance, and low vertical wind shear.

Low-pressure area

area of low pressurelow pressure arealow pressure
Tropical cyclogenesis requires six main factors: sufficiently warm sea surface temperatures (at least ), atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to develop a low-pressure center, a pre-existing low-level focus or disturbance, and low vertical wind shear.

Wind shear

windshearvertical wind shearshear
Tropical cyclogenesis requires six main factors: sufficiently warm sea surface temperatures (at least ), atmospheric instability, high humidity in the lower to middle levels of the troposphere, enough Coriolis force to develop a low-pressure center, a pre-existing low-level focus or disturbance, and low vertical wind shear.

Tropical cyclone basins

basinSouth Pacific basinbasins
Tropical cyclones tend to develop during the summer, but have been noted in nearly every month in most basins.

Climate

climaticclimate systemclimates
Climate cycles such as ENSO and the Madden–Julian oscillation modulate the timing and frequency of tropical cyclone development.