The South Atlantic convergence zone, or SACZ, is an elongated axis of cloud

Cloud

A cloud is a visible mass of liquid droplets or frozen crystals made of water and/or various chemicals suspended in the atmosphere above the surface of a planetary body. They are also known as aerosols. Clouds in Earth's atmosphere are studied in the cloud physics branch of meteorology...

s, precipitation

Precipitation (meteorology)

In meteorology, precipitation In meteorology, precipitation In meteorology, precipitation (also known as one of the classes of hydrometeors, which are atmospheric water phenomena is any product of the condensation of atmospheric water vapor that falls under gravity. The main forms of precipitation...

, and convergent winds oriented in a northwest-southeast manner across southeast Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is the largest country in South America. It is the world's fifth largest country, both by geographical area and by population with over 192 million people...

 into the southwest Atlantic ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

. By definition, the feature is a monsoon trough

Monsoon trough

The monsoon trough is that portion of the Intertropical Convergence Zone which extends into or through a monsoon circulation, as depicted by a line on a weather map showing the locations of minimum sea level pressure, and as such, is a convergence zone between the wind patterns of the southern and...

. It is strongest in the warm season. Thunderstorm

Thunderstorm

A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

 activity along the feature magnifies over three or more days when the Madden-Julian Oscillation

Madden-Julian oscillation

The Madden–Julian oscillation ' is the largest element of the intraseasonal variability in the tropical atmosphere. It is a large-scale coupling between atmospheric circulation and tropical deep convection...

 passes into the region, due to the enhanced upper divergence. Low level winds over Rondônia

Rondônia

Rondônia is a state in Brazil, located in the north-western part of the country. To the west is a short border with the state of Acre, to the north is the state of Amazonas, in the east is Mato Grosso, and in the south is Bolivia. Its capital is Porto Velho. The state was named after Candido Rondon...

 are tied to the strength of this zone, where westerly wind

Wind

Wind is the flow of gases on a large scale. On Earth, wind consists of the bulk movement of air. In outer space, solar wind is the movement of gases or charged particles from the sun through space, while planetary wind is the outgassing of light chemical elements from a planet's atmosphere into space...

 anomalies correlate to active phases of the South America

South America

South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

n monsoon

Monsoon

Monsoon is traditionally defined as a seasonal reversing wind accompanied by corresponding changes in precipitation, but is now used to describe seasonal changes in atmospheric circulation and precipitation associated with the asymmetric heating of land and sea...

, while easterly wind anomalies indicate breaks of activity along the SACZ. The feature is also strongest with negative anomalies in the sea surface temperature pattern lie over the southern Atlantic ocean, while opposite conditions prevail across the northern Atlantic ocean.