South Atlantic tropical cyclone

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South Atlantic tropical cyclones 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.[1] 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.[2] These tropical cyclones will be given identifiers starting with "SL" in the future.[3]

According to a study published in 2008, there were 92 subtropical cyclones in the Southern Atlantic between 1957 and 2008.[4] Below is a list of notable South Atlantic tropical and subtropical cyclones.

South Atlantic tropical and subtropical cyclones[edit]

March 1974 Subtropical Depression[edit]

Subtropical depression (SSHWS)
Duration March 27, 1974 – March 29, 1974
Peak intensity 45 km/h (30 mph) (1-min)  988 hPa (mbar)

Similar to the later formation of Catarina, a strong dipole-blocking structure (or Rex blocking) persisted for nine and a half days over the western South Atlantic Ocean in late March 1974, which decreased wind shear across the region. A low pressure area developed over the Amazon basin, and intensified as it moved southeastward over open waters, establishing a very large closed circulation. Deep convection increased near the center, and banding features began developing. The system resembled a subtropical cyclone, and there were hints of a warm-core. It was unable to intensify further, due to the weakening of the ridge component of the blocking -which led to shear increasing- and water temperatures decreasing. Unlike Catarina, the system maintained a southeast motion throughout its duration.[5]

1991 Angola Tropical Cyclone[edit]

Tropical storm (SSHWS)
Duration April 10, 1991 – April 14, 1991
Peak intensity 65 km/h (40 mph) (1-min) 

A low pressure area formed over the Congo Basin on April 9. The next day it moved offshore northern Angola with a curved cloud pattern. It moved westward over an area of warm waters, and the circulation became better defined. According to the United States National Hurricane Center, the system was probably either a tropical depression or a tropical storm at its peak intensity. On April 14, the system rapidly dissipated as it was absorbed into a large squall line.[6][7] Of the few South Atlantic tropical cyclones that have existed, this is the only one in the eastern South Atlantic on record.

January 2004 Tropical Depression[edit]

Tropical depression (SSHWS)
Duration January 18, 2004 – January 21, 2004
Peak intensity 55 km/h (35 mph) (1-min)  1003 mbar (hPa)

A small area of convection developed on a trough of low pressure in mid January off Brazil. It organized and appeared to become a tropical depression on January 18. The next morning, it had a small CDO and well-defined bands, and the system, either a weak tropical storm or a strong tropical depression, likely reached its peak. Located 150 nautical miles (280 km) southeast of Salvador, Brazil, it weakened as upper level shear, typical for the basin, prevailed. The depression moved inland on the 20th as a circulation devoid of convection, and dissipated the next day over Brazil, where it caused heavy rains and flooding.[8]

Cyclone Catarina[edit]

Category 2 tropical cyclone (SSHWS)
Duration March 24, 2004 – March 28, 2004
Peak intensity 155 km/h (100 mph) (1-min)  972 mbar (hPa)
Main article: Cyclone Catarina

Cyclone Catarina was an extraordinarily rare tropical cyclone, forming in the southern Atlantic Ocean in March 2004.[2] Just after becoming a hurricane, it hit the southern coast of Brazil in the state of Santa Catarina on the evening of March 28, with winds estimated near 155 kilometres per hour (96 mph), making it a Category 2-equivalent on the Saffir-Simpson Hurricane Scale. The cyclone killed 3 to 10 people and caused millions of dollars in damage in Brazil.

At the time, the Brazilians were taken completely by surprise, and were at first in utter disbelief that an actual tropical cyclone could have formed in the South Atlantic despite the insistence of the National Hurricane Center otherwise. Later, they were convinced, and adopted the name "Catarina" for the storm, after Santa Catarina state. This event is considered by some meteorologists to be a nearly once-in-a-lifetime occurrence.

February 2006 Tropical Storm[edit]

Tropical storm (SSHWS)
Duration February 21, 2006 – February 24, 2006
Peak intensity 100 km/h (65 mph) (1-min) 

A small area of convection 600 miles southeast of Rio de Janeiro 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 low-level circulation center 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.[9]

January 2009 Subtropical Storm[edit]

Subtropical storm (SSHWS)
Duration January 28, 2009 – January 31, 2009
Peak intensity 65 km/h (40 mph) (1-min) 

A cold-core mid to upper-level trough 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.[10]

Tropical Storm Anita[edit]

Tropical storm (SSHWS)
Duration March 8, 2010 – March 12, 2010
Peak intensity 85 km/h (50 mph) (1-min)  995 mbar (hPa)

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 Laboratory 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.[11] 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.[12]

November 2010 Subtropical Cyclone[edit]

Subtropical storm (SSHWS)
Duration November 16, 2010 – November 18, 2010
Peak intensity Winds unknown  1005 mbar (hPa)

On November 16, a cold-core mid to upper-level trough 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.[13] [14] The subtropical cyclone became a weak trough on November 19, according to the CPTEC.[15] 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.[citation needed]

Subtropical Storm Arani[edit]

Subtropical storm (SSHWS)
Duration March 10, 2011 – March 16, 2011
Peak intensity 85 km/h (50 mph) (1-min)  989 mbar (hPa)

Early on March 14, 2011, the Navy Hydrographic Center-Brazilian Navy (SMM), in coordination with the National Institute of Meteorology, were monitoring an organizing area of convection near the southeast coast of Brazil.[16] Later that day a low pressure area developed just east of Vitória, Espírito Santo,[17] and by 1200 UTC, the system organized into a subtropical depression, located about 140 km (90 mi) east of Campos dos Goytacazes.[18] Guided by a trough and a weak ridge to its north, the system moved slowly southeastward over an area of warm waters,[19][20] intensifying into Subtropical Cyclone Arani on March 15,[21] as named by the Brazilian Navy Hydrographic Center.[22] The storm was classified as 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.[23]

Prior to developing into a subtropical cyclone, Arani produced torrential rains over portions of southeastern Brazil, resulting in flash flooding and landslides. Significant damage was reported in portions of Espírito Santo, though specifics are unknown.[24] Increased swells along the coast prompted ocean travel warnings.[25]

December 2013 Subtropical Cyclone[edit]

Subtropical storm (SSHWS)
Duration December 23, 2013 – December 25, 2013
Peak intensity Winds unknown  1008 mbar (hPa)

On December 23, the CPTEC (Centro de Previsão de Tempo e Estudos Climáticos) identified that a subtropical cyclone formed at 1200 UTC south of Rio de Janeiro.[26] On December 24, the cyclone moved southwards, maintaining a minimum pressure of 1,008 hPa (29.8 inHg).[27][28] On December 25 at 1200 UTC, the subtropical cyclone degenerated into a remnant low.[28][29]

February 2014 Subtropical Depression[edit]

Subtropical depression (SSHWS)
Clockwise vortex
Duration February 20, 2014 – February 22, 2014
Peak intensity 45 km/h (30 mph) (1-min)  1008 mbar (hPa)

On February 20, the Navy Hydrography Center briefly classified a subtropical depression about 925 km (575 mi) southeast of Rio de Janeiro. The system moved southward, with a minimum pressure of 1,008 hPa (29.8 inHg) and winds of about 45 km/h (30 mph).[30] On February 22, the subtropical depression dissipated.

Listed by month[edit]

There have been 12 officially recorded tropical and subtropical cyclones in the South Atlantic Ocean since 1974.

See also[edit]

References[edit]

  1. ^ Chris Landea (July 13, 2005). "FAQ: Why doesn't the South Atlantic Ocean experience tropical cyclones?". NOAA. Retrieved May 14, 2009. 
  2. ^ a b College of Earth and Mineral Sciences (2004). "Upper-level lows". Pennsylvania State University. Retrieved 2009-05-14. 
  3. ^ http://www.ofcm.noaa.gov/nhop/09/pdf/04-chap4-09.pdf
  4. ^ Aviva J. Braun (2008). "Subtropical Storms in the South Atlantic Basin and their Correlation with Australian East-Coast Cyclones" (PDF). American Meteorological Society. Retrieved November 19, 2010. 
  5. ^ McTaggart Cowan, Ron; Bosart, Lance; Davis, Christopher; Atallah, Eyad; Gyakum, John; Emanual, Kerry (2006). "Analysis of Hurricane Caterina (2004)". Monthly Weather Review (American Meteorological Society) 134 (11): 3048–9. Bibcode:2006MWRv..134.3029M. doi:10.1175/MWR3330.1. 
  6. ^ National Hurricane Center (1991). II. Tropical cyclone activity in the Atlantic Basin: A. Overview (Diagnostic Report of the National Hurricane Center: June and July 1991). National Oceanic and Atmospheric Administration. p. 10, 13, 14. http://hdl.handle.net/2027/uiug.30112005414658. Retrieved May 12, 2013.
  7. ^ Marcel Leroux (2001). "Tropical Cyclones". The Meteorology and Climate of Tropical Africa. Praxis Publishing Ltd. p. 314. Retrieved 2013-03-28. 
  8. ^ Gary, Padgett. "Monthly Global Tropical Cyclone Summary January 2004". Retrieved 2010-04-15. 
  9. ^ Padgett, Gary. "February 2006 Tropical Weather Summary". Retrieved 2009-01-28. 
  10. ^ Padgett, Gary (April 7, 2009). "January 2009 Tropical Weather Summary". Retrieved 2010-04-15. 
  11. ^ http://www.webcitation.org/5o7vOfDzk
  12. ^ (Portuguese) "Monitoramento - Ciclone tropical na costa gaúcha" (in Portuguese). Brazilian Meteorological Service. March 2010. 
  13. ^ (Portuguese) "Análise Sinótica: 17/11/2010-00Z" (in Portuguese). CPTEC - INPE. November 2010. Archived from the original on November 19, 2010. 
  14. ^ (Portuguese) "Baixas começam a semana "em alta"" (in Portuguese). METSUL. November 2010. Archived from the original on November 19, 2010. 
  15. ^ "Boletim Technico 19/11/10 - 00z". CPTEC. 
  16. ^ Chura, Ledesma, Davison (2011-03-14). "South American Synopsis". Hydrometeorological Prediction Center. Retrieved 2011-03-14. 
  17. ^ Chura, Ledesma, Davison (2011-03-14). "South American Synopsis (2)". Hydrometeorological Prediction Center. Retrieved 2011-03-14. 
  18. ^ Marine Meteorological Service (2011-03-14). "Weather and Sea Bulletin Referent Analysis 1200 GMT - 14/MAR/2011". Brazil Navy Hydrographic Center. Retrieved 2011-03-14. 
  19. ^ Chura, Ledesma, Davison (2011-03-15). "South American Synopsis (3)". Hydrometeorological Prediction Center. Retrieved 2011-03-15. 
  20. ^ Chura, Ledesma, Davison (2011-03-15). "South American Synopsis (4)". Hydrometeorological Prediction Center. Retrieved 2011-03-15. 
  21. ^ Marine Meteorological Service (2011-03-15). "Severe Weather Warnings". Brazil Navy Hydrographic Center. Retrieved 2011-03-15. 
  22. ^ "Severe Weather Warnings - March 11, 2011". Brazilian Navy. 2011-03-11. Retrieved 15 March 2011. 
  23. ^ Rob Gutro (2011-03-15). "NASA's Aqua Satellite Spots Rare Southern Atlantic Sub-tropical Storm". National Aeronautics and Space Administration. Retrieved 2011-03-15. 
  24. ^ (Portuguese) Unattributed (March 16, 2011). "Arani – tempestade subtropical afasta-se da costa do ES". Climatempo. Retrieved March 19, 2011. 
  25. ^ (Portuguese) Unattributed (March 16, 2011). "Após formar um olho, ciclone subtropical Arani perde força nesta quarta". Jornal De Tempo. Retrieved March 19, 2011. 
  26. ^ (Portuguese) "Análise Sinótica – 23/12/2013" (in Portuguese). CPTEC - INPE. December 23, 2013. Retrieved February 24, 2014. 
  27. ^ (Portuguese) "Análise Sinótica – 24/12/2013" (in Portuguese). CPTEC - INPE. December 24, 2013. Retrieved February 24, 2014. 
  28. ^ a b (Portuguese) "SÍNTESE SINÓTICA DEZEMBRO DE 2013" (in Portuguese). CPTEC - INPE. Retrieved February 24, 2014. 
  29. ^ (Portuguese) "Análise Sinótica – 25/12/2013" (in Portuguese). CPTEC - INPE. December 25, 2013. Retrieved February 24, 2014. 
  30. ^ Weather and Sea Bulletin Referent Analysis 1200 UTC for 20 Feb 2014. Navy Hydrography Center/Brazilian Navy. 20 February 2014 http://www.webcitation.org/6NXfB7UBu |url= missing title (help). Retrieved 21 February 2014. 

External links[edit]