South Atlantic tropical cyclone
Encyclopedia
South Atlantic tropical cyclone
s are unusual weather events that occur in the southern hemisphere. Strong wind shear
(which disrupts cyclone formation) and a lack of weather disturbances favorable for tropical cyclone development make any hurricane-strength cyclones extremely rare. If a "hurricane season" were to be demarcated in the South Atlantic, it would most likely be the opposite of the North Atlantic season, from November to the end of April with mid-March being the peak when the oceans are warmest in the Southern Hemisphere. These tropical cyclones would be given identifiers starting with SL in the future.
According to a study published in 2008, there were 92 subtropical cyclones in the Southern Atlantic between 1957 and 2008. Below is a list of notable South Atlantic tropical and subtropical cyclones.
was tracked into an area of relatively low shear and marginal 26°C waters on February 23, 2006. The wave had deep convection, was able to form a closed LLC and had 35 mi/h (56 km/h) winds as measured by Quikscat on February 24, 2006. These characteristics were operationally recognized for three hours before high shear began to tear the system apart, just short of the six hours required to be officially declared a tropical depression. The storm was estimated at have peaked in intensity with winds of 65 mph (100 km/h), equivalent to a strong tropical storm, early on February 23. While under study, the system was referred to as 90L Invest. The shear would eventually cause the system to dissipate later that night.
in phase with a low-level warm-core low
formed a system
over Uruguay
and Rio Grande do Sul
state in Brazil
and moved eastward into the South Atlantic
. Winds exceeded 54 knots on the coast of Uruguay and extreme southern Rio Grande do Sul. The storm produced rainfall in 24 hours of 300 mm or more in some locations of Rocha
(Uruguay) and southern Rio Grande do Sul. The weather station owned by MetSul Weather Center in Morro Redondo, Southern Brazil, recorded 278.2 mm in a 24-hour period.
Fourteen deaths and thousands of evacuees are attributed to the storm with an emergency declared in four cities.
began monitoring the system as a system of interest under the designation of 90Q. The National Hurricane Center
also began monitoring the system as Low SL90. During the afternoon of March 9, the system had attained an intensity of 55 km/h (35 mph) and a barometric pressure of 1000 hPa (mbar). It was declared a tropical storm on March 10 and became extratropical late on March 12. Anita's accumulated cyclone energy
was estimated at 2.0525 by the Florida State University. There was no damage associated to the storm, except high sea in the coasts of Rio Grande do Sul and Santa Catarina. Post mortem, the cyclone was given the name "Anita" by private and public weather centers from Southern Brazil.
in phase with a low-level warm-core low
formed a system
over Uruguay
and Rio Grande do Sul
state in Brazil
and moved southeastward into the South Atlantic
, where it slightly deepened. The system brought locally heavy rains in southern Brazil and northeast of Uruguay that exceeded 200 milimeters in a few hours in some locations of Southern Rio Grande do Sul northwest of Pelotas. Damages and flooding were observed in Cerrito, São Lourenço do Sul and Pedro Osório. Bañado de Pajas, departament of Cerro Largo in Uruguay, recorded 240 mm of rain. Then, it started to drift southeastward, over open waters of the South Atlantic, where it gradually weakened.
The subtropical cyclone became a weak trough on November 19, according to the CPTEC. The low pressure system that originated the subtropical cyclone favored hail storms that affected dozens of cities in Southern Brazil, mainly in Rio Grande do Sul state, on November 15. Over a dozen towns declared emergency due to the damages. In some places, the hail accumulated 30 cm (one foot) and could be seen in the fields even four days after the storm.
(SMM), in coordination with the National Institute of Meteorology, were monitoring an organizing area of convection near the southeast coast of Brazil. Later that day a low pressure area
developed just east of Vitória, Espírito Santo
, and by 1200 UTC
, the system organized into a subtropical depression
, located about 140 km (90 mi) east of Campos dos Goytacazes
.
Guided by a trough
and a weak ridge
to its north, the system moved slowly southeastward over an area of warm waters, intensifying into Subtropical Cyclone Arani on March 15, as named by the Brazilian Navy Hydrographic Center. The storm was classified subtropical, due to the convection being located east of the center.
On March 16, Arani began experiencing 25 knots of wind shear due to the another frontal system bumping it from behind.
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...
s are unusual weather events that occur in the southern hemisphere. Strong wind shear
Wind shear
Wind shear, sometimes referred to as windshear or wind gradient, is a difference in wind speed and direction over a relatively short distance in the atmosphere...
(which disrupts cyclone formation) and a lack of weather disturbances favorable for tropical cyclone development make any hurricane-strength cyclones extremely rare. If a "hurricane season" were to be demarcated in the South Atlantic, it would most likely be the opposite of the North Atlantic season, from November to the end of April with mid-March being the peak when the oceans are warmest in the Southern Hemisphere. These tropical cyclones would be given identifiers starting with SL in the future.
According to a study published in 2008, there were 92 subtropical cyclones in the Southern Atlantic between 1957 and 2008. Below is a list of notable South Atlantic tropical and subtropical cyclones.
Subtropical Cyclone of March 1974
A small area of convection 600 miles southeast of Rio de JaneiroRio de Janeiro
Rio de Janeiro , commonly referred to simply as Rio, is the capital city of the State of Rio de Janeiro, the second largest city of Brazil, and the third largest metropolitan area and agglomeration in South America, boasting approximately 6.3 million people within the city proper, making it the 6th...
was tracked into an area of relatively low shear and marginal 26°C waters on February 23, 2006. The wave had deep convection, was able to form a closed LLC and had 35 mi/h (56 km/h) winds as measured by Quikscat on February 24, 2006. These characteristics were operationally recognized for three hours before high shear began to tear the system apart, just short of the six hours required to be officially declared a tropical depression. The storm was estimated at have peaked in intensity with winds of 65 mph (100 km/h), equivalent to a strong tropical storm, early on February 23. While under study, the system was referred to as 90L Invest. The shear would eventually cause the system to dissipate later that night.
Subtropical Storm of January 2009
A cold-core mid to upper-level troughTrough (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...
in phase with a low-level warm-core low
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
formed a system
Pressure system
A pressure system is a region of the Earth's atmosphere where air pressure is a relative peak or lull in the sea level pressure distribution. The surface pressure at sea level varies minimally, with the lowest value measured and the highest recorded...
over Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
and Rio Grande do Sul
Rio Grande do Sul
Rio Grande do Sul is the southernmost state in Brazil, and the state with the fifth highest Human Development Index in the country. In this state is located the southernmost city in the country, Chuí, on the border with Uruguay. In the region of Bento Gonçalves and Caxias do Sul, the largest wine...
state in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and moved eastward into the South Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
. Winds exceeded 54 knots on the coast of Uruguay and extreme southern Rio Grande do Sul. The storm produced rainfall in 24 hours of 300 mm or more in some locations of Rocha
Rocha Department
Rocha is a department in the east of Uruguay. It has natural beauties like Cabo Polonio, Valizas, Santa Teresa. Rocha is well known for its beach towns which swell during the summer holidays...
(Uruguay) and southern Rio Grande do Sul. The weather station owned by MetSul Weather Center in Morro Redondo, Southern Brazil, recorded 278.2 mm in a 24-hour period.
Fourteen deaths and thousands of evacuees are attributed to the storm with an emergency declared in four cities.
Tropical Storm Anita
On March 8 2010, a previously extratropical cyclone developed tropical characteristics and was classified as a subtropical cyclone off the coast of southern Brazil. The following day, the United States Naval Research LaboratoryUnited States Naval Research Laboratory
The United States Naval Research Laboratory is the corporate research laboratory for the United States Navy and the United States Marine Corps and conducts a program of scientific research and development. NRL opened in 1923 at the instigation of Thomas Edison...
began monitoring the system as a system of interest under the designation of 90Q. The National Hurricane Center
National Hurricane Center
The National Hurricane Center , located at Florida International University in Miami, Florida, is the division of the National Weather Service responsible for tracking and predicting weather systems within the tropics between the Prime Meridian and the 140th meridian west poleward to the 30th...
also began monitoring the system as Low SL90. During the afternoon of March 9, the system had attained an intensity of 55 km/h (35 mph) and a barometric pressure of 1000 hPa (mbar). It was declared a tropical storm on March 10 and became extratropical late on March 12. Anita's accumulated cyclone energy
Accumulated cyclone energy
Accumulated cyclone energy is a measure used by the National Oceanic and Atmospheric Administration to express the activity of individual tropical cyclones and entire tropical cyclone seasons, particularly the North Atlantic hurricane season. It uses an approximation of the energy used by a...
was estimated at 2.0525 by the Florida State University. There was no damage associated to the storm, except high sea in the coasts of Rio Grande do Sul and Santa Catarina. Post mortem, the cyclone was given the name "Anita" by private and public weather centers from Southern Brazil.
Subtropical Storm of November 2010
On November 16, a cold-core mid to upper-level troughTrough (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...
in phase with a low-level warm-core low
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
formed a system
Pressure system
A pressure system is a region of the Earth's atmosphere where air pressure is a relative peak or lull in the sea level pressure distribution. The surface pressure at sea level varies minimally, with the lowest value measured and the highest recorded...
over Uruguay
Uruguay
Uruguay ,officially the Oriental Republic of Uruguay,sometimes the Eastern Republic of Uruguay; ) is a country in the southeastern part of South America. It is home to some 3.5 million people, of whom 1.8 million live in the capital Montevideo and its metropolitan area...
and Rio Grande do Sul
Rio Grande do Sul
Rio Grande do Sul is the southernmost state in Brazil, and the state with the fifth highest Human Development Index in the country. In this state is located the southernmost city in the country, Chuí, on the border with Uruguay. In the region of Bento Gonçalves and Caxias do Sul, the largest wine...
state in Brazil
Brazil
Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...
and moved southeastward into the South Atlantic
Atlantic Ocean
The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...
, where it slightly deepened. The system brought locally heavy rains in southern Brazil and northeast of Uruguay that exceeded 200 milimeters in a few hours in some locations of Southern Rio Grande do Sul northwest of Pelotas. Damages and flooding were observed in Cerrito, São Lourenço do Sul and Pedro Osório. Bañado de Pajas, departament of Cerro Largo in Uruguay, recorded 240 mm of rain. Then, it started to drift southeastward, over open waters of the South Atlantic, where it gradually weakened.
The subtropical cyclone became a weak trough on November 19, according to the CPTEC. The low pressure system that originated the subtropical cyclone favored hail storms that affected dozens of cities in Southern Brazil, mainly in Rio Grande do Sul state, on November 15. Over a dozen towns declared emergency due to the damages. In some places, the hail accumulated 30 cm (one foot) and could be seen in the fields even four days after the storm.
Subtropical Storm Arani
Early on March 14 2011, the Navy Hydrographic Center-Brazilian NavyBrazilian Navy
The Brazilian Navy is a branch of the Brazilian Armed Forces responsible for conducting naval operations. It is the largest navy in Latin America...
(SMM), in coordination with the National Institute of Meteorology, were monitoring an organizing area of convection near the southeast coast of Brazil. Later that day a low pressure area
Low pressure area
A low-pressure area, or "low", is a region where the atmospheric pressure at sea level is below that of surrounding locations. Low-pressure systems form under areas of wind divergence which occur in upper levels of the troposphere. The formation process of a low-pressure area is known as...
developed just east of Vitória, Espírito Santo
Espírito Santo
Espírito Santo is one of the states of southeastern Brazil, often referred to by the abbreviation "ES". Its capital is Vitória and the largest city is Vila Velha. The name of the state means literally "holy spirit" after the Holy Ghost of Christianity...
, and by 1200 UTC
Coordinated Universal Time
Coordinated Universal Time is the primary time standard by which the world regulates clocks and time. It is one of several closely related successors to Greenwich Mean Time. Computer servers, online services and other entities that rely on having a universally accepted time use UTC for that purpose...
, the system organized into a subtropical depression
Subtropical cyclone
A subtropical cyclone is a weather system that has some characteristics of a tropical and an extratropical cyclone. As early as the 1950s, meteorologists were unclear whether they should be characterized as tropical or extratropical cyclones. They were officially recognized by the National...
, located about 140 km (90 mi) east of Campos dos Goytacazes
Campos dos Goytacazes
Campos dos Goytacazes is a municipality and city located in the northern area of Rio de Janeiro State, Brazil, with a population of 463,545 inhabitants. Its area is 4,031.910 km², which makes it the largest municipality in the state and its elevation is 14 m...
.
Guided by a 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...
and a weak ridge
Ridge (meteorology)
A ridge is an elongated region of relatively high atmospheric pressure, the opposite of a trough....
to its north, the system moved slowly southeastward over an area of warm waters, intensifying into Subtropical Cyclone Arani on March 15, as named by the Brazilian Navy Hydrographic Center. The storm was classified subtropical, due to the convection being located east of the center.
On March 16, Arani began experiencing 25 knots of wind shear due to the another frontal system bumping it from behind.
Listed by month
There have been 9 officially recorded tropical and subtropical cyclones in the South Atlantic Ocean since 1974.| Month | Number of recorded storms in the South Atlantic Ocean |
|---|---|
| January | 2 |
| February | 1 |
| March | 4 |
| April | 1 |
| May | 0 |
| June | 0 |
| July | 0 |
| August | 0 |
| September | 0 |
| October | 0 |
| November | 1 |
| December | 0 |
See also
- Hurricane Huron
- List of notable tropical cyclones#Unusual landfalls
- Mediterranean tropical cyclone
- North Atlantic tropical cyclone
- Tropical cyclogenesis#Unusual areas of formation