Rain in Rio Grande do Sul will continue. Lajeado is once again suffering from flooding half a year after the major historic floods of the Taquari River in the second half of 2023. Rivers are expected to rise even higher with the prospect of intense to extreme rain in the coming days. | AGEU KEHRWALD
Rio Grande do Sul is once again experiencing the drama of the waters with flooded cities, floods with overflowing rivers, deaths and damage, repeating the scenes from the second half of last year that marked the height of the 2023-2024 El Niño event and which was responsible for floods of historic proportions in the state.
The scenario is very complicated with the prospect of more rain adding to what has already rained, which will make the situation critical with considerable material damage and a high risk of losing more human lives, warns MetSul Meteorologia.
The rainfall accumulated in 96 hours until late afternoon today in several cities in Rio Grande do Sul were extreme and even extraordinary in some municipalities with accumulated in just four days above 400 mm. Cemaden’s rain gauges indicated 448 mm in Segredo, 410 mm in Lagoa Bonita do Sul, 371 mm in Faxinal do Soturno, 329 mm in Santa Maria, 318 mm in Cachoeira do Sul, 313 mm in Candelária and Nova Palma, 312 mm in Arroio do Tigre and 310 mm in Lajeado.
Many cities accumulated between 200 mm and 300 mm from the Center to the East of the state, like almost the entire Greater Porto Alegre which is 200 mm to 250 mm. By the end of the afternoon, 246 mm had rained since the weekend in Sapucaia do Sul, 236 mm in Canoas, 229 mm in Gravataí, 203 mm in Viamão, 200 mm in Novo Hamburgo, and 183 mm in Eldorado do Sul and Alvorada. These are volumes equivalent to two months of rain in just four days.
In the National Institute of Meteorology network, volumes in 96 hours until the end of the afternoon totaled 287 mm in Santa Maria, 279 mm in São Gabriel, 271 mm in Bento Gonçalves, 237 mm in Canela, 226 mm in Caçapava do Sul, 215 mm in Rio Pardo, 206 mm in Campo Bom and 203 mm in Porto Alegre.
The numbers make it clear. We are facing an exceptional rain event in Rio Grande do Sulfavored by an unusual climate situation in South America with an unusual hot air mass for this time of year over the states of Central Brazil.
What is already serious will get worse. The scenario we see at MetSul Meteorologia, without mincing words, is likely to evolve into an extremely serious one. Several cities must face a situation from calamity to disaster. In places where it has already rained 200 mm to 400 mm, data from numerical models indicate another 150 mm to 300 mm or more by Saturday.
The map below shows the rain projection for the WRF model initialized with the European model for 72 hours between 9am today and 9am Friday.
METSUL
This would make in just one week the accumulation in part of the state reaches between 500 and 700 mm, considering that it has already rained 300 mm to 450 mm in several municipalities. To get an idea of what these numbers represent, andIn just one week, part of the state of Rio Grande do Sul should have more rain than it usually falls, on average, in all the autumn months combined. More than that, some cities must have a third of what rains in an entire year in one week.
Map of the Global Flood Awareness System (GloFAS), the European Union’s global flood monitoring system, which uses data from meteorological and hydrological models, projects high risk (red) for most of the state’s rivers and extreme risk (purple) for the basins of the Jacuí, Ibicuí and Vacacaí rivers. | COPERNICUS
The trend is for the situation to worsen with more intense rain in the second half of the week because the state will be between a strong cold air mass in Argentina and an exceptionally hot air mass over Brazil, which will reinforce instability with a cold front.
The hot air, which today raised the temperature to 35ºC in the Northwest of Rio Grande do Sul, will cause highs never before seen in May in the coming days in the Southeast of Brazil with afternoons up to 10ºC warmer than the month’s normal. The cold air will bring intense cold in Argentina with lots of snow in the Andes. The cold air advances over the state and will be felt most on Friday with the dawn of low lows in Campanha and the South, and lower highs in the afternoon.
The thermal contrast and the advance of the cold front on Thursday reinforce the instability with heavy rain, especially in the Northern Half, where the sources of the rivers that cut through the valleys and are already leaving the bed are located. The rain in several regions between this Wednesday and Thursday becomes torrential again with high volumes in a short period of time, which can generate flash floods. There is also a risk of isolated thunderstorms of hail and gales, mainly from the Center to the North of the state on Thursday during the advance of the cold front.
WRF model suggests high risk of storms at the beginning of Thursday with the movement of the cold front through the Center and North of Rio Grande do Sul | METSUL
Thus, the rain in Rio Grande do Sul is unrelenting and continues on this holiday Wednesday with the approach of the cold front. There will be heavy to torrential showers during the day in several locations, especially in the Northwest, West, Center, South and East of the state. Again, the accumulation in some municipalities can be very high in a short period of time, with lightning and strong thunderstorms. Moments of improvement are predicted and, in the North and Northeast of the state, even openings.
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