RIO DE JANEIRO, BRAZIL – A thick dust cloud hit Ribeirão Preto, Franca, Barretos and other major cities in São Paulo’s interior on Sunday afternoon, September 26. Strong gusts of wind were also reported. The cloud was later dispersed by heavy rainfall which reached 50 millimeters in some cities.
According to MetSul meteorologist Estael Sias, the phenomenon is common in Asian countries, where it is known as “haboob.” It is caused by rain storms with strong winds that, when coming into contact with dry soil, find remnants of patch burns, dust and vegetation, which ultimately create a “steamroller” of dirt that can reach up to 10 kilometers in height.
“First comes the storm and storm cloud, which generated the more horizontal wind current and stirred up all this debris. Since it hasn’t rained in that area for months, there is much dust, the soil and vegetation are dry, and the fires have also helped,” Sias explains.
Satellites from the National Institute of Meteorology showed that the city of Franca registered strong winds of up to 60 kph (36 mph) on Sunday. In Ribeirão Preto wind gusts reached 95 kpm (57 mph). The region was also on alert for storms with up to 30 millimeters of precipitation per hour and risk of hail, like the storm that hit parts of the capital of São Paulo the day before, causing damage to crops, fallen tree branches and floods.
Although Sias explains that this is a natural event due to the weather conditions, she also points out that it is more typical of Asian countries and not as common in southeastern Brazil.
However, she says that the phenomenon tends to disperse on its own: “The wind that follows the storm helps to spread this sand further and it dissolves, like fog, which is slow but helped by the wind.”