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An Overview and Brief History of Southern Hemisphere Tropical Cyclones
(Released June 2012)

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  by Adam Arnold  

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Southeast Pacific and South Atlantic Regions

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Closer to the Americas, the southeast Pacific and southern Atlantic basins are generally free of tropical cyclone activity. No tropical cyclone in history has been recorded in the southeastern Pacific east of roughly 160°W longitude. This is mostly due to the very cold waters of the Peruvian Current off of the west coast of South America. For both areas, the ITCZ is generally too far north towards the equator where the Coriolis force necessary for tropical cyclone formation is not strong enough. In addition, wind shear is very strong across both regions due to a more equatorward presence of the jet stream.

Despite the very negative factors towards tropical cyclone formation, there have been a few recorded incidents of tropical cyclone formation in the south Atlantic. On 10 April 1991, a tropical storm formed off of the coast of Angola. It most likely peaked at a strength of an estimated 40 knots as it drifted west-southwestwards towards the open Atlantic, dissipating on 12 April 1991. This tropical storm was the only recorded tropical cyclone to form in the southeastern Atlantic close to Africa, as usually the cold waters of the Benguela Current prevent tropical cyclone formation.

Cyclone Catarina is the flagship historical tropical cyclone of the south Atlantic. Forming on 24 March 2004 in unusually favorable conditions as a subtropical cyclone several hundred miles east-southeast of Florianopolis, Brazil, Catarina moved slowly westward, obtaining full tropical characteristics on 25 March 2004. After becoming a full tropical cyclone, Catarina was better able to consolidate its structure and intensify while it moved westwards towards the Brazilian coast. On 26 March 2004, Catarina became the equivalent of a category one hurricane on the Saffir-Simpson scale. During this time, Brazilian meteorologists refused to consider Catarina a tropical cyclone due to the lack of recorded cyclones near the Brazilian coast, ignoring the evidence and suggestions provided by the National Hurricane Center in Miami. Despite this, they still warned the residents of Santa Catarina state, from which the cyclone was unofficially named, and surrounding areas that a strong storm (furação) was headed their way. On 28 March 2004, Catarina reached its maximum strength of 90 KTS, a category 2 hurricane on the Saffir-Simpson scale. Shortly after, Catarina made landfall near Torres, Rio Grande do Sul. Because the area had not seen a tropical cyclone in recorded history, and due to the low-income nature of many of the residents (living on an annual salary of around US $200 (2004)), the impact was unusually devastating for the strength at which Catarina hit. Fortunately authorities evacuated residents close to the coast prior to the storm. In all, approximately 36,000 homes were damaged (with almost 1,000 completely destroyed) (Marcelino-2004 9), 3 people died, and 38 people were injured (USA Today 2004).  The agricultural sector of the area was devastated, with some areas losing their entire banana and rice crops (Marcelino-2004 11).
Path of Cyclone Catarina
The track of Cyclone Catarina using the color scheme from the Saffir-Simpson Hurricane Scale.

After Catarina, an effort through the WMO and NHC in Miami was organized to better train Brazilian meteorologists for the threat of tropical cyclones. This resulted in more standardized classification procedures for the south Atlantic basin. These improved efforts have been put to the test twice since Catarina with Tropical Storm Anita in March 2010 and Subtropical Storm Arani in March 2011. Anita was the first tropical cyclone to be classified with a new numbering suffix of SL, while Arani was the first officially named tropical or subtropical cyclone in the south Atlantic. Anita stayed mostly off the coast of southern Brazil, causing high seas and some rain in the coastal areas of Santa Catarina and Rio Grande do Sul states. Arani caused flooding and landslides in portions of Espirito Santo state before moving southeastwards away from the Brazilian coast.

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