The Portuguese search term vai chover amanhã was observed in Brazil’s search market on September 1.
However, this record does not mean that the same rain fell across Brazil, nor does it refer to the weather on September 11.
The key to the forecast at the time was a subtropical low-pressure system off the southern coast and rain and temperature conditions that varied greatly by region.
3-Line Summary
1. The September 1 rain forecast varied by region
2. Unstable conditions were forecast for the South, Southeast, and Midwest
3. A forecast for a date that has passed is not the current weather
A subtropical low-pressure system off the southern coast on the first day of September
The forecast issued on September 1 by INMET (Brazil’s National Institute of Meteorology) explained that a new subtropical low-pressure system would form off Brazil’s southern coast, creating conditions conducive to rain and thunderstorms in the South, Southeast, and Midwest. In this material, the subtropical low-pressure system was presented as a factor organizing unstable weather and cloud bands.
At the time of reporting, O GLOBO (a Brazilian daily newspaper) also reported the possibility of rain and thunderstorms in the South, Southeast, and Midwest that day. However, this was not the actual precipitation result but a forecast for September 1. Even if the search term appeared connected to the question “Will it rain tomorrow?”, the evidence remaining is only the outlook from that point in time.
INMET also assessed that temperatures could drop sharply in the South as a cold, dry air mass advanced. The fact that rain was mentioned did not by itself mean a warmer or more humid day. The explanation was that the effects of rain clouds and cold air could appear together depending on the region.
O GLOBO also reported a trend toward decreasing cloud cover in some areas of the South. Even though there was one factor—the formation of a low-pressure system—the forecast did not indicate that rain clouds and temperature changes would move in the same direction in every region.
The rain news extended from the South to the Midwest, but the scope varied
In the Southeast, early-morning showers and localized thunderstorms were forecast for São Paulo State and southern Rio de Janeiro State. O GLOBO also mentioned the possibility of gusty winds and hail in western São Paulo, the Triângulo Mineiro region of Minas Gerais State, southern Goiás State, and parts of Mato Grosso State and Mato Grosso do Sul State. By contrast, northern Espírito Santo State and north-central Minas Gerais State were described as relatively outside the rain conditions despite abundant cloud cover.
The daytime high in São Paulo city was given as 22 degrees, while Belo Horizonte in the same Southeast was forecast to reach 34 degrees. Even within areas where rain was forecast, temperature conditions differed this much. This is why it is difficult to interpret a city’s daily weather from the phrase “rain in the Southeast” alone.
The Midwest could not be viewed as one single block either. INMET presented conditions for rain and thunderstorms in Mato Grosso do Sul State and southern Goiás State, and expected localized showers in the south-central parts of Mato Grosso State and Goiás State. At night, the possibility of localized rain was also mentioned as far as the Federal District and north-central Goiás State. In the Federal District and central Goiás State, clouds were expected to increase during the day, but the meteorologist cited by O GLOBO said clearer signs of rain could emerge from Wednesday onward.
In the South, showers and isolated thunderstorms were expected in Santa Catarina State, eastern Rio Grande do Sul State, and Paraná State, with strong winds forecast especially along the coast. However, southern and western Rio Grande do Sul State were reported to be clearing as cold, dry air moved in, with no further rain forecast. Even within the same South, whether rain would occur differed by area.
In the North and Northeast, the key was heat more than ‘rain’
Along the Northeastern coast, rain was expected in Rio Grande do Norte State, Paraíba State, Pernambuco State, and Alagoas State. O GLOBO explained that precipitation could be at ordinary levels but could amount to a significant total if accumulated over a day. However, the interior of the Northeast—Maranhão State and Piauí State—and western and northwestern Bahia State were presented as following a hotter, drier pattern.
A forecast also indicated that the high in Piauí State could reach 41 degrees. INMET likewise mentioned intense heat in the interior Northeast, particularly Piauí State. Even within the same Northeast, it was a day when localized rain along the coast and high temperatures and dryness inland were forecast simultaneously.
The North was generally dominated by dry, hot weather, but showers caused by heat and humidity could be concentrated in west-central and northern Amazonas State. The possibility of isolated rain was separately presented for Acre State and southern Rondônia State. The forecast region and time of day mattered more than the single sentence “It will rain in Brazil.”
Globo Rural (a Brazilian agricultural media outlet) pointed out that September is a transition period in Brazil, from a dry, cold winter to the return of rain and higher temperatures. The meteorologist cited by the outlet explained that El Niño and above-average Atlantic Ocean temperatures affect atmospheric instability and moisture supply. The outlet also forecast that September precipitation would be concentrated heavily in the South, while parts of the Southeast, Midwest, and Northeast could also see more rain than average.
This monthly trend is not an announcement confirming whether a specific city will actually receive precipitation. Even in the short-term forecast for September 1, some parts of the South were presented as seeing the rain end, while in the North and Northeast, heat and dryness were more pronounced than rain depending on the region. The fact that the search-observation market was Brazil and the actual regions covered by the forecast at the time need to be viewed separately.
References
Tags #vai_chover_amanhã #BrazilWeather #BrazilRainForecast #September1Weather #SubtropicalLowPressureSystem #SouthernBrazil #SoutheasternBrazil #Central-WesternBrazil #NortheasternBrazil #ElNiño #PrecipitationForecast #ThunderstormForecast #TemperatureForecast