Rare in Summer, Bomb Cyclone Forms on Brazil-Uruguay Border

RIO DE JANEIRO, BRAZIL – An extratropical cyclone with explosive features is forming near the border between Brazil and Uruguay, in southeastern Rio Grande do Sul. The phenomenon, known as a bomb cyclone, is a rare event in summer.

“It occurs when there is an explosive formation with a drop in atmospheric pressure of over 24 hPa in 24 hours, that is, when the pressure drops at a rate of 1 hPa per hour. This phenomenon occurs at higher latitudes, further south, and typically in winter months so it is completely atypical,” explains meteorologist Estael Sias.

The Brazilian region most affected by the phenomenon will be southern Rio Grande do Sul. “Wind will still gather force particularly in the south and east. Rain will lessen in most areas. Only the far south may experience heavy rainfall. Worse on the high seas”, he adds.

On Thursday morning, the city of Santa Vitória do Palmar reported winds of 80km/h, according to MetSul Meteorology. But gusts may become even stronger, reaching 100km/h. In the Metropolitan Region of Porto Alegre, wind speed may reach 70 km/h.

The Navy issued a wind warning until the end of Friday and high tides until Saturday.

The extratropical cyclone also gives rise to a cold front, which is responsible for heavy rain and is located in Santa Catarina and Paraná on Thursday. Instability is expected to ascend and reach the states of the Southeast and Midwest on Friday, Saturday and Sunday.