Strong storms and powerful wind gusts are poised to impact Brazil’s southern and southeastern regions, as a low-pressure system forming near the coast is expected to evolve into an extratropical cyclone over the Atlantic Ocean by late January 2025. This weather phenomenon typically develops offshore, without directly traversing the continental landmass, yet it significantly contributes to atmospheric instability across several Brazilian states.
The system is forecast to generate broad areas of instability over key regions including Santa Catarina, Paraná, São Paulo, Rio de Janeiro, and Espírito Santo. These conditions elevate the potential for widespread rainfall and severe weather events, prompting authorities to advise residents to prepare for adverse conditions.
As January 30th, 2025, progresses, the extratropical cyclone will shift its position, extending its influence to the coast of Rio de Janeiro. This movement is expected to intensify existing storm activity, potentially leading to localized heavy rainfall and strong winds across various municipalities.
Extratropical cyclone to bring severe weather to southern Brazil
A complex atmospheric setup, characterized by a persistent low-pressure system near Brazil’s coast, is the primary driver behind the formation of a significant extratropical cyclone. While this system primarily operates over the Atlantic, its indirect effects are substantial, creating conditions ripe for severe weather across mainland Brazil. The interaction between this offshore cyclone and continental atmospheric patterns is crucial for understanding the forecast instability.
Forecasters indicate that the cyclone’s influence is amplified by a secondary area of low pressure developing over Paraguay. This continental system is projected to expand eastward, affecting Mato Grosso do Sul, Paraná, and São Paulo, further increasing the risk of intense thunderstorms in these populous states during the final days of January.
Storms intensify across southeastern states
Heavy rainfall poses a significant risk for the southeast and southern coastal areas of São Paulo state starting early on January 30th, 2025. Specific localities like Itararé, Registro, Três Barras, and Peruíbe are identified as particularly vulnerable to strong downpours and potential flooding.
By the afternoon, these intense weather patterns are anticipated to spread, reaching the São Paulo metropolitan area. Residents in the capital and surrounding cities should prepare for locally intense thunderstorms, which may include frequent lightning strikes and powerful thunder.
Further inland, the typical summer-like afternoon showers are also expected to impact the interior and northern parts of São Paulo. Cities such as Jundiaí, Indaiatuba, Bocaina, Lençóis Paulista, Piracicaba, Ribeirão Preto, and São José dos Campos are likely to experience heavy rain and associated risks.
Cold front develops, increasing instability by Saturday
On January 31st, 2025, the extratropical cyclone will become well-developed and continue its trajectory deeper into the Atlantic Ocean, progressively moving away from Brazil’s coastline. Despite its oceanic position, the system will still generate a cold front near the shores of Rio de Janeiro and Espírito Santo, maintaining a degree of atmospheric instability.
The transport of moisture onto the continent, particularly over eastern São Paulo, will result in a notably unstable day. This includes increased cloud cover and scattered rain showers starting early in the morning, affecting areas such as Greater São Paulo.
In the state of Rio de Janeiro, the day is expected to be muggy, with rising nebulosity leading to morning rain, including in the Greater Rio area. However, the intensity of these rain showers is predicted to increase significantly during the afternoon, especially across the northern parts of the state.
Between the afternoon and evening of January 31st, severe storms are also projected to impact areas in southern Espírito Santo. These conditions could bring isolated but potent thunderstorms, accompanied by lightning and strong winds, presenting hazards to local communities.
Coastal warnings: winds and rough seas expected
Throughout the weekend of February 1st, 2025, the extratropical cyclone will continue its offshore movement, heading towards the southern region’s coast while maintaining a considerable distance from the mainland. This persistent offshore activity will result in notable changes to coastal conditions.
Coastal areas of São Paulo and the southern litoral of Rio de Janeiro are forecast to experience moderate wind gusts, with wave heights nearing one meter. These conditions could affect marine activities and coastal recreational plans, advising caution for beachgoers and small vessel operators.
Potential for a second cyclone in early February
The initial days of February 2025 are likely to maintain a pattern of high temperatures coupled with intermittent but strong thunderstorms across the Southeast. Atmospheric models are currently indicating the potential for a new extratropical cyclone to form around February 4th. This evolving scenario is being closely monitored by meteorologists and could be linked to the development of another cold front off the coast between São Paulo and Rio de Janeiro. Such a system has the potential to contribute significantly to the organization of a new episode of the South Atlantic Convergence Zone (ZCAS) during the first week of February, a weather pattern known for bringing prolonged periods of heavy rain to parts of Brazil.
Preparing for severe impacts
Authorities emphasize the importance of preparedness for residents in the affected regions. Key recommendations include:
* Securing loose objects outdoors to prevent wind damage.
* Avoiding unnecessary travel during peak storm periods.
* Staying informed about local weather alerts from official channels.
* Having emergency kits ready in case of power outages or flooding.
These measures are crucial for mitigating risks associated with the intense weather events forecast for late January and early February 2025 across southern and southeastern Brazil.
