earth science

South American Tornado Alley

South American Tornado Alley is a earth science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand South American Tornado Alley rather than just read about it. In short: 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. The area was named by the São Leopoldo Urban Climatology Station Network.

Key takeaways

South American Tornado Alley belongs to earth science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect South American Tornado Alley to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of South American Tornado Alley from memory before moving on to harder problems.

Reference excerpt

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. The area was named by the São Leopoldo Urban Climatology Station Network.

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. This region (especially central Argentina) is considered one of the areas with a high probability of tornado occurrence in the world. It is estimated that between 250-400 tornadoes are generated in this area per year, being more common in autumn and spring.

Causes NASA conducted a study in 2006, using information provided by its satellites, to identify the areas where the most intense storms occur. 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. A similar situation occurs east of the Rocky Mountains in the United States. 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.

Location The Tornado Alley covers a large area of South America: its central core is located in Argentina (northern Buenos Aires province, central and eastern Córdoba, southern and central Santa Fe, west of Entre Ríos), 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. The Alley encompasses the following areas:

In Argentina The provinces of:

La Pampa North and northeast of the province of Río Negro South of the province of San Luis Much of the province of Santa Fe Córdoba Entre Ríos Province of Buenos Aires Southeast of the province of Santiago del Estero Southeast of the province of Chaco Central and eastern part of the province of Formosa Corrientes Much of the province of Misiones In Brazil The states of:

Rio Grande do Sul Santa Catarina Paraná Mato Grosso do Sul Interior of the state of São Paulo South-central Minas Gerais In southern Paraguay The departments of:

Ñeembucú Itapúa Misiones 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. 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. 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. 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, a tornado formed, killing approximately 500 people, 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 and also claimed the lives of 80 people. Their intensity is purely speculative since the Fujita scale, based on systematic survey damage, was only introduced in the United States in 1971 and its use in other countries took several more years. On September 30, 1991, a narrow, high-end F4 tornado struck parts of the municipalities of Itu (SP) and Salto (SP). 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.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with South American Tornado Alley

Start with the simplest possible case. Write down what South American Tornado Alley claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In earth science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to South American Tornado Alley before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about South American Tornado Alley ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of South American Tornado Alley

In research: South American Tornado Alley appears in earth science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses South American Tornado Alley in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: South American Tornado Alley is common in secondary-school and first-year university syllabi. It links to neighbouring topics Climate of South America, Pampas, Regions of South America, so understanding it makes those chapters shorter.
In everyday life: Look for South American Tornado Alley outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study South American Tornado Alley in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what South American Tornado Alley means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
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Frequently asked questions

What is South American Tornado Alley in simple terms?

Why does South American Tornado Alley matter?

Because it connects several earth science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study South American Tornado Alley?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on South American Tornado Alley.