MetSul Meteorologia reinforced, this Sunday, the 28th, the warning about a scenario of serious hydrological and meteorological risk in Rio Grande do Sul with excessive to extreme rain and a very high probability of river floods and floods at the end of April and, especially, in the first week of May.
An exceptionally warm air mass over Brazil will intensify over the center of the country this week under an atmospheric blocking pattern. At the same time, colder air will be acting over Argentina for several days, generating a huge thermal contrast in the continent’s mid-latitudes.
Since Rio Grande do Sul will be in the transition zone between the two air masses, hot and cold, instability will be frequent with the expectation of a lot of rain. Sometimes colder air from the South will advance towards the State, sometimes warmer air from the North will enter, and this constant day-to-day variation will generate successive areas of instability with abundant precipitation.
The scenario is very similar to that of last year’s meteorological spring, during the height of El Niño, when extreme rain events with flooding hit Rio Grande do Sul in the months of September, October and November under atmospheric blockages associated with powerful waves of heat in the Central-West and Southeast of Brazil.
The rain that will fall at the end of April and the beginning of May will add to what has already fallen this weekend and in the last few days in Rio Grande do Sul, when it rained a lot and even excessively in some places.
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River floods and floods
As it has already rained a lot and the indications are that it will rain a lot more in the State, there will inevitably be river floods and floods, assesses MetSul. The tendency is that several basins (rivers) should reach alert and flood quotas in Rio Grande do Sul and in several regions this first week.
The GloFAS projection indicates that the vast majority of rivers in Rio Grande do Sul have a high (red) to extreme (purple) risk of flooding in the next ten days.
Residents of the valleys, especially Taquari and Caí, severely punished by last year’s floods, naturally ask whether there will be floods like the one in 2023. The risk of flooding in the Taquari and Caí Rivers is high, but in the short term (seven to ten days) The likelihood of a repeat of floods as severe as those in September or November is remote to low.
Extreme rain will bring floods and geological risks
Given the precipitation scenario presented, despite variations in volumes and distribution of rain in the numerical modeling package, it is certain that there will be impacts on the population and, in some municipalities, serious ones. The persistence of rain for several days, in addition to river flooding, will bring flooding and flooding. Rain with accumulations as extreme as expected also brings geological risks.
The risk of landslides in hillside areas will be very high.. There must also be barriers falling that could result in partial or total blockages of state and federal highways. Some roads, particularly municipal and rural ones, are expected to become impassable with likely sections and ridges covered by water.
With the prospect of strong currents, flooded sections should be strictly avoided by drivers at risk of fatal accidents. Another concern is that this episode of excessive rain occurs at a time when the summer harvest is still being harvested, compromising farmers’ activities and even causing losses. So many consecutive days of rain and such high volumes must cause serious problems for the field. Crops will even be underwater in several municipalities.
