South American Tornado Alley

The Tornado corridor of South America is the region where cold, dry winds from the Andes and Patagonia meet warm, humid winds from the Amazon and the Chaco, creating conditions conducive to the formation of tornadoes.:[1] The area was named by the São Leopoldo Urban Climatology Station Network.[2]

It includes the states of Rio Grande do Sul, Santa Catarina, Paraná, São Paulo, all of south-central Minas Gerais, Mato Grosso do Sul in Brazil, as well as central and northern Argentina, Uruguay, Paraguay, and the south-central portion of Bolivia.[3] This region (especially central Argentina) is considered one of the areas with a high probability of tornado occurrence in the world.[4] It is estimated that up to 50 tornadoes are generated in this area per year, being more common in autumn and spring.[5][6]

Causes

NASA conducted a study in 2006, using information provided by its satellites, to identify the areas where the most intense storms occur.[7] It concluded that these occur mainly east of the Andes Mountains in Argentina. In this area, cold winds from Patagonia and Antarctica converge with warm air masses from Brazil, Paraguay, and northern Argentina, and with dry air coming from the Andes Mountains. The clash between these different air masses occurs mainly in the pampa plain and generates conditions for intense storms, hail, and tornadoes.[8] A similar situation occurs east of the Rocky Mountains in the United States.[7]

Due to insufficient weather radar coverage, as well as the region's low population density, it is not possible to accurately detect the number of tornadoes that occur annually in this area. Generally, only those sighted by people are recorded.[9]

Location

The Tornado Alley covers a large area of South America:[3] its central core is located in Argentina (northern Buenos Aires province, central and eastern Córdoba, southern and central Santa Fe, west of Entre Ríos[10]), as well as all of Uruguay. Within this zone, there is a higher probability of strong tornadoes forming; as the distance increases, the number and intensity of storms decreases.[5] The Alley encompasses the following areas:

In Argentina

The provinces of:[11]

In Brazil

The states of:[12]

In southern Paraguay

The departments of:

In addition, it covers the entire territory of Uruguay.

Measurement

In this region, conditions are favorable for the formation of tornadoes and intense storms, due to the large extent of the pampas plain. Cold air from Patagonia and Antarctica collides with warm, humid air coming from Brazil, northern Argentina, and Paraguay, as well as dry air from the Andes.[3] This combination produces intense storms that very frequently reach supercell status, and many generate intense hail and tornadoes of varying intensities, mainly F0, F1, and F2.

The tornadoes in this corridor are compared to those in the region known as the "Dixie Alley Corridor" in the United States, which includes the states of Mississippi, Alabama, Georgia, Tennessee, Arkansas, Florida, and Louisiana. This is because, most of the time, tornadoes in this region are produced by high-precipitation supercells, therefore being enveloped in curtains of rain (mainly in western and southwestern Paraná, northwestern and northern Rio Grande do Sul, and western Santa Catarina), which makes the visibility of the phenomena difficult or almost nil. This characteristic is extremely dangerous, as tornadoes enveloped in rain cause more deaths and are more difficult to predict. However, in the Campinas Region, most tornadoes are produced by classic or low-precipitation supercells. Additionally, tornadoes in the Southern region of Brazil are mostly events of low available convective potential energy (CAPE) and high wind shear (0-1 km).

In southern and southeastern Brazil, they generally occur between April and November, although they appear more frequently between April and June. In central Argentina, tornadoes are most frequent in spring and summer.[13] North of this area, intense storms begin to occur in late August, and because it is a more humid and warm zone, they can occur at any time of year. The plain encompassing the Chaco and the Pampas is less extensive and populated than that of North America, and the number of tornadoes recorded is lower. Furthermore, in South America, unlike the United States, Canada, and Europe, there are no measurements of the number of tornadoes that occur in each storm, nor are there advance warnings.[9] There are no measurements or statistics indicating the number of tornadoes generated each year in the Tornado Alley, but it is known that the number is lower than in the United States. They are of lower intensity, as most are F0, F1, and F2 scale tornadoes, with the maximum recorded being F5.

Registers

The most intense tornadoes were those of Encarnación (Paraguay) on September 20, 1926, when an F5 tornado formed, killing approximately 500 people,[14][15][16]making it the deadliest tornado recorded in South American history, and the San Justo tornado (Santa Fe province, Argentina) on January 10, 1973, which was the strongest tornado recorded outside the United States (F5) and also claimed the lives of 80 people.[17]

On September 30, 1991, a narrow, high-end F4 tornado struck parts of the municipalities of Itu (SP) and Salto (SP).[18] Well-built brick houses were flattened, vehicles were thrown hundreds of meters and mutilated beyond recognition, and thousands of trees were completely stripped of their bark and uprooted. A large luxury hotel and agricultural schools were completely devastated. Although classified as F3, meteorologists note that widespread F4 damage likely occurred with this tornado. The event caused 16 deaths and over 300 injuries.[19]

The 1993 Buenos Aires tornado outbreak was an outbreak (QLCS type) of around 100 tornadoes that affected the southern area of Buenos Aires province. Between the evening and night of Tuesday, April 13 of 1993, an extraordinary system of severe convective storms affected the localities of Trenque Lauquen, Pehuajó, Hipólito Yrigoyen, Carlos Casares, Bolívar, Daireaux, General Lamadrid, Olavarría, Tapalqué, Azul, Laprida, Benito Juárez, Tandil, Necochea, Lobería, Balcarce, General Alvarado and General Pueyrredon. The most affected localities were Henderson (F3), Urdampilleta (F3) and Mar del Plata (F2). This succession of tornadoes had intensities ranging from F0 to F3 and produced severe damage along northwest to southeast-oriented strips. The local area affected exceeded 4,000 square kilometers (1500 sq mi). The phenomenon was popularly called "La Noche De Los 100 Tornados" (the night of 100 tornadoes) and it holds the record for being the largest tornado outbreak ever recorded in the southern hemisphere.[20][21][22][23]

In Brazil, the most intense tornadoes occurred in Guaraciaba (Santa Catarina) in 2009 and Nova Laranjeiras (Paraná) in 1997. In Nova Laranjeiras, a tornado classified as F4 resulted in the total destruction of more than 80% of residences, many of which were left with only the floors remaining. In Guaraciaba, F4 damage was widespread and very significant, as trees were uprooted, masonry houses were wiped off the map, and objects were found hundreds of kilometers from their original location.[24]

The worst violent tornadoes that occurred much further north in the South American tornado corridor and outside the mid-latitudes were the events in Ivinhema (MS)/1989 as an F4, Ponta Porã (MS)/1999, Brasilândia-Panorama (MS and SP)/2015 as an F2, and Ribeirão Preto (SP)/1994 also as an F2.

See also

References

  1. ^ "Argentina: "El pasillo de los Tornados"". reporteplatense.com.ar (in Spanish). 2025-09-04. Archived from the original on July 15, 2020. Retrieved 2025-12-16.
  2. ^ "Folha Online - Cotidiano - Instituto prevê ocorrência de novos tornados no país - 31/05/2005". www1.folha.uol.com.br. Archived from the original on February 23, 2021. Retrieved 2025-12-16.
  3. ^ a b c Henrique, Daniel; Felipe, Rafael. "Condicionantes Atmosféricos da Tempestade Ocorrida em 21 de abril de 2008 na Cidade de Maringá (PR) e suas Conseqüências" (PDF). Archived from the original (PDF) on December 21, 2014.
  4. ^ Aguiar, Alexandre. "Tornados - Duas realidades muito diferentes". Metroclima.{{cite web}}: CS1 maint: url-status (link)
  5. ^ a b "Tornados en Argentina, ayer y hoy". Pronóstico Extendido (in Spanish). October 9, 2012. Retrieved 2025-12-16.
  6. ^ "Meteorología de Buenos Aires". Retrieved 2025-12-16.
  7. ^ a b "NASA Satellite Identifies the World's Most Intense Thunderstorms". www.nasa.gov. Archived from the original on 2023-05-13. Retrieved 2025-12-16.
  8. ^ "El pasillo de los tornados, la zona inestable de Sudamérica". EL PAIS. 2016-04-18. Retrieved 2025-12-16.
  9. ^ a b "Meteorología carece de sistema de detección y predicción de tornados". Última Hora (in Spanish). 2015-01-19. Retrieved 2025-12-16.
  10. ^ "Pasillo de los Tornados - Pasado y presente". Google My Maps. Retrieved 2025-12-16.
  11. ^ "Tornados en Argentina" (in Spanish).
  12. ^ Henrique, Daniel (August 17, 2012). "Tornados e trombas-d'água no Brasil : modelo de risco e proposta de escala de avaliação de danos". 1library.org (in Brazilian Portuguese). Campinas. Retrieved 2025-12-16.
  13. ^ Moutinho, Sofia (2012). "Brasil, alvo de tornados". Ciência Hoje (in Brazilian Portuguese). Retrieved 2025-12-16.
  14. ^ "El tornado de Encarnación - Interior - ABC Color". www.abc.com.py (in Spanish). Retrieved 2025-12-16.
  15. ^ "EL CICLÓN DE 1926 SE COBRÓ MÁS DE 400 VIDAS Y DESTRUYÓ ENCARNACIÓN". Última Hora (in Spanish). 2012-09-23. Retrieved 2025-12-16.
  16. ^ "La Nación / La primavera de 1926, cuando un tornado casi borra a Encarnación". www.lanacion.com.py (in Spanish). Retrieved 2026-02-22.
  17. ^ Ellitoral.com. "Se cumplen 40 años del tornado que azotó a San Justo" (in Spanish). Retrieved 2025-12-16.
  18. ^ Itu.com.br. "Histórias de tempestades em Itu". Itu.com.br (in Brazilian Portuguese). Retrieved 2026-02-22.
  19. ^ Itu.com.br. "Histórias de tempestades em Itu". Itu.com.br (in Brazilian Portuguese). Retrieved 2025-12-16.
  20. ^ "A 25 años de la noche de los tornados". www.smn.gob.ar. Archived from the original on 2020-10-20. Retrieved 2025-12-16.
  21. ^ "Un día como hoy, hace 29 años, Argentina vivía la oleada de tornados más numerosa fuera de los EEUU" [On a day like today, 29 years ago, Argentina experienced the largest tornado outbreak outside the United States] (in Spanish). Retrieved 2025-04-17.
  22. ^ Redacción. "La noche de los 100 tornados" [the night of the 100 tornadoes]. argentina.gob.ar (in Spanish). Retrieved 2025-04-17.
  23. ^ "Trágico martes 13" [Tragic Tuesday the 13th] (in Spanish).
  24. ^ "Folha de S.Paulo - Vendaval deixa 80% das casas no chão - 16/06/97". www1.folha.uol.com.br. Retrieved 2025-12-16.
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