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South Atlantic tropical cyclone

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Tracks of named South Atlantic tropical and subtropical cyclones since 2004

South Atlantic tropical cyclones are unusual weather events that occur in the Southern Hemisphere. Strong wind shear, which disrupts the formation of cyclones, as well as a lack of weather disturbances favorable for development in the South Atlantic Ocean, make any strong tropical system extremely rare, and Hurricane Catarina in 2004 is the only recorded South Atlantic hurricane in history. Storms can develop year-round in the South Atlantic, with activity peaking during the months from November through May. Since 2011, the Brazilian Navy Hydrographic Center has assigned names to tropical and subtropical systems in the western side of the basin, near the eastern coast of Brazil, when they have sustained wind speeds of at least 65 km/h (40 mph), the generally accepted minimum sustained wind speed for a disturbance to be designated as a tropical storm in the North Atlantic basin. Below is a list of notable South Atlantic tropical and subtropical cyclones.

Theories concerning infrequency of occurrence

It was initially thought that tropical cyclones did not develop within the South Atlantic.[1] Very strong vertical wind shear in the troposphere is considered a deterrent.[2] The Intertropical Convergence Zone drops one to two degrees south of the equator,[3] not far enough from the equator for the Coriolis force to significantly aid development. Water temperatures in the tropics of the southern Atlantic are cooler than those in the tropical north Atlantic.[4]

Although they are rare, during April 1991 the United States' National Hurricane Center (NHC) reported that a tropical cyclone had developed over the Eastern South Atlantic.[1][5] In subsequent years, a few systems were suspected to have the characteristics needed to be classified as a tropical cyclone, including in March 1994 and January 2004.[6][7] During March 2004, an extratropical cyclone formally transitioned into a tropical cyclone and made landfall on Brazil, after becoming a Category 2 hurricane on the Saffir–Simpson hurricane wind scale. While the system was threatening the Brazilian state of Santa Catarina, a newspaper used the headline "Furacão Catarina", which was originally presumed to mean "furacão (hurricane) threatening (Santa) Catarina (the state)".[1] After international presses started monitoring the system, "Hurricane Catarina" has formally been adopted.

At the Sixth WMO International Workshop on Tropical Cyclones (IWTC-VI) in 2006, it was questioned if any subtropical or tropical cyclones had developed within the South Atlantic before Catarina.[7] It was noted that suspect systems had developed in January 1970, March 1994, January 2004, March 2004, May 2004, February 2006, and March 2006.[7] It was also suggested that an effort should be made to locate any possible systems using satellite imagery and synoptic data; however, it was noted that this effort may be hindered by the lack of any geostationary imagery over the basin before 1966.[7] A study was subsequently performed and published during 2012, which concluded that there had been 63 subtropical cyclones in the Southern Atlantic between 1957 and 2007.[8] During January 2009, a subtropical storm developed in the basin, and in March 2010, a tropical storm developed, which was named Anita by the Brazilian public and private weather services.[9][10] In 2011, the Brazilian Navy Hydrographic Center started to assign names to tropical and subtropical cyclones that develop within its area of responsibility, to the west of 20°W, when they have sustained wind speeds of at least 65 km/h (40 mph).[11]

Notable storms and impacts

Pre-2010s

1991 Angola tropical storm

Tropical storm (SSHWS)
 
Duration10 April 1991 – 14 April 1991
Peak intensity65 km/h (40 mph) (1-min);

A low-pressure area formed over the Congo Basin on 9 April. The next day it moved offshore northern Angola with a curved cloud pattern. It moved westward over an area of warm waters while 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 14 April, the system rapidly dissipated, as it was absorbed into a large squall line.[5][12] This is the only recorded tropical cyclone in the eastern South Atlantic.

Hurricane Catarina

Category 2 hurricane (SSHWS)
 
Duration24 March 2004 – 28 March 2004
Peak intensity155 km/h (100 mph) (1-min);
972 hPa (mbar)
Main article: Hurricane Catarina

Hurricane Catarina was an extraordinarily rare hurricane-strength tropical cyclone, forming in the southern Atlantic Ocean in March 2004.[13] Just after becoming a hurricane, it hit the southern coast of Brazil in the state of Santa Catarina on the evening of 28 March, with winds up to 195 kilometres per hour (121 mph) making it a Category 2-equivalent cyclone on the Saffir–Simpson hurricane scale.[14] Catarina killed 3 to 11 people and caused millions of dollars in damage in Brazil.[15]

At the time, Brazilians were taken completely by surprise, and were initially skeptical that an actual tropical cyclone could have formed in the South Atlantic. Eventually, however, they were convinced, and adopted the previously unofficial 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.

2010s

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List of storms, by decade

See also

Wikimedia Commons has media related to South Atlantic tropical cyclones.

References

  1. ^ a b c Padgett, Gary. "Monthly Tropical Cyclone Summary March 2004". Archived from the original on 17 December 2015. Retrieved 7 February 2015.
  2. ^ Landsea, Christopher W (13 July 2005). "Subject: Tropical Cyclone Names: G6) Why doesn't the South Atlantic Ocean experience tropical cyclones?". Tropical Cyclone Frequently Asked Question. United States National Oceanic and Atmospheric Administration's Hurricane Research Division. Archived from the original on 27 March 2015. Retrieved 7 February 2015.
  3. ^ Gordon E. Dunn & Banner I. Miller (1960). Atlantic Hurricanes. Louisiana State University Press. p. 33. ASIN B0006BM85S.
  4. ^ Atlantic Oceanographic and Meteorological Laboratory, Hurricane Research Division. "Frequently Asked Questions: How do tropical cyclones form?". National Oceanic and Atmospheric Administration. Retrieved 26 July 2006.
  5. ^ a b National Hurricane Center (1991). McAdie, Colin J; Rappaport, Edward N (eds.). 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. pp. 10–14. hdl:2027/uiug.30112005414658. Retrieved 12 May 2013.
  6. ^ Padgett, Gary. "Monthly Tropical Cyclone Summary January 2004". Archived from the original on 17 December 2015. Retrieved 7 February 2015.
  7. ^ a b c d Topic 2a: The Catarina Phenomenon (PDF). The Sixth WMO International Workshop on Tropical Cyclones (IWTC-VI). San José, Costa Rica: World Meteorological Organization. 2006. pp. 329–360. Archived from the original (PDF) on 4 March 2016. Retrieved 7 February 2015.
  8. ^ Evans, Jenny L; Braun, Aviva J (2012). "A Climatology of Subtropical Cyclones in the South Atlantic". Journal of Climate. 25 (21). American Meteorological Society: 7328–7340. Bibcode:2012JCli...25.7328E. doi:10.1175/JCLI-D-11-00212.1.
  9. ^ Padgett, Gary (7 April 2009). "January 2009 Tropical Weather Summary". Retrieved 15 April 2010.
  10. ^ Padgett, Gary. "Monthly Global Tropical Cyclone Tracks March 2010". Archived from the original on 17 December 2015. Retrieved 7 February 2015.
  11. ^ "Normas Da Autoridade Marítima Para As Atividades De Meteorologia Marítima" (PDF) (in Portuguese). Brazilian Navy. 2011. Archived from the original (PDF) on 6 February 2015. Retrieved 5 October 2018.
  12. ^ Marcel Leroux (2001). "Tropical Cyclones". The Meteorology and Climate of Tropical Africa. Praxis Publishing Ltd. p. 314. ISBN 978-3-540-42636-3. Retrieved 28 March 2013.
  13. ^ College of Earth & Mineral Sciences (2004). "Upper-level lows". Pennsylvania State University. Archived from the original on 3 March 2016. Retrieved 14 May 2009.
  14. ^ Gary Padgett (2004). "March 2004 Tropical Cyclone Summary". Thomas R. Metcalf (Australian Severe Weather). Retrieved 23 October 2008.
  15. ^ Jefferson Bernardes (30 March 2004). "First South Atlantic hurricane hits Brazil". USA Today. Retrieved 23 February 2009.
Wikimedia Commons has media related to South Atlantic tropical cyclones.
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