page_title: South Atlantic tropical cyclone
section_title: 2004–2009
hierarchical_section_title: South Atlantic tropical cyclone / Other systems / 2004–2009
caption_attribution_description: English: South Atlantic Tropical Storm on February 23, 2006
context_page_description: 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. South Atlantic storms have developed year-round, with activity peaking during the months from November through May in this basin. 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, 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.
context_section_description: During 2004, the large-scale conditions over the South Atlantic were more conducive than usual for subtropical or tropical systems, with 4 systems noted. The first possible tropical cyclone developed within a trough of low pressure, to the southeast of Salvador, Brazil on January 18. The system subsequently displayed a small central dense overcast (CDO) and was suspected to be at the peak of its development as either a tropical depression or a tropical storm during the next day. The system was subsequently affected by some strong shear, before it moved inland and weakened along the coast of Brazil before it was last noted during January 21. Within Brazil the system caused heavy rain and flooding with a state of emergency declared in Aracaju, after the river overflowed and burst its banks which flooded homes, destroyed crops and caused parts of the highway to collapse. However, it was noted that not all of the heavy rain and impacts were attributable to the system, as a large monsoon low covered much of Brazil at the time. The second system was a possible hybrid cyclone that developed near south-eastern Brazil between March 15–16. Hurricane Catarina was the third system, while the fourth system had a well-defined eye like structure, and formed off the coast of Brazil on March 15, 2004.
  On February 22, 2006, a baroclinic cyclone intensified quickly and was estimated to have peaked with 1-minute sustained wind speeds of 105 km/h (65 mph), after radar data showed that the system had developed an eye and banding. However, there were questions about how tropical the system was, as it did not separate from the westerlies or the baroclinic zone it was in. Between March 11–17, 2006, another system with a warm core developed and moved southward along the South Atlantic Zone, before dissipating.
  Two subtropical cyclones affected both Uruguay and Rio Grande do Sul state in Brazil between 2009 and 2010. On January 28, 2009, a cold-core mid to upper-level trough in phase with a low-level warm-core low formed a system and moved eastward into the South Atlantic. The storm produced rainfall in 24 hours of 300 mm (12 in) 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 (10.95 in) in a 24-hour period. The storm caused fourteen deaths and the evacuation of thousands, with an emergency declared in four cities. It lasted until February 1, when the cyclone became extratropical.
caption: MODIS visible satellite image of a possible February 2006 tropical storm
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