MetSul Meteorologia warns that meteorological conditions will be very adverse and dangerous in the next few hours in the South of Brazil with a high risk of heavy to intense rain with high volumes and also isolated storms that can bring gales in localized points, capable of causing damage. A process of cyclogenesis begins (formation of an extratropical cyclone) that will give rise to a sea storm very close to the coast of Rio Grande do Sul.
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The intense instability is a consequence of an area of low pressure that has moved in the last few hours from the Northeast of Argentina to Rio Grande do Sul and that during the night of this Thursday and the beginning of Friday will deepen into the territory of Rio Grande do Sul before give rise to an extratropical cyclone in the southeast of the state this Friday.
The low pressure area that acts over Rio Grande do Sul brought rain in all regions in the last few hours and was heavy in several locations, accumulating only during this holiday 50 mm to 100 mm in municipalities such as Santiago, Alegrete, Frederico Westphalen, Erechim, Uruguaiana, Itaqui, Horizontina, etc. The east wind still blew strong with sometimes intense gusts in several places.
Why are the next few hours worrying? The low pressure area this Friday will give rise to an extratropical cyclone at the beginning of the day very close to the coast, just east and southeast of Chuí. During the day, the cyclone intensifies on the coasts of Uruguay and Rio Grande do Sul with central pressure falling to values below 990 hPa.
The deepening of low pressure over Rio Grande do Sul and the subsequent formation of the cyclone pushes colder air, which this afternoon brought very low temperatures for November in Central Argentina, to the North and Northeast of Argentina this Friday.
As a result, a cold front associated with the cyclone is organized over the south of Brazil and advances through the region with strong to intense rain and wind storms, which in isolation can be strong to severe, tonight and during Friday. There is potential for isolated storm cells to form that could trigger strong windstorms.
The risk is greater of severe weather tonight and during Friday in the Northern Half of Rio Grande do Sul, in Santa Catarina and Paraná, but the storms will advance to the Central-West and Southeast of Brazil, where localized storms with gales and rain should be expected strong, especially from Friday afternoon to night.
The cold front, as it moves through southern Brazil, will also bring a lot of rain. It rains a lot on Thursday night in sectors of the North and East Half of Rio Grande do Sul, including the Porto Alegre area. During Friday, as the front advances through the South, intense rain will hit many areas of Santa Catarina and Paraná. There is a risk of extreme volumes of 100 mm to 200 mm in a few hours in parts of the state of Santa Catarina, for example.
The maps below show rain projections for Thursday night, and early morning, morning, afternoon and night this Friday, using the European Meteorological Center (ECMWF) model, which shows how intense the instability will be with very high volumes in a short period of time. period in some areas.
Excessive volumes of rain over the next few hours in southern Brazil could bring flooding, flash floods, rising streams and streams, and river flooding. Relief areas may still experience landslides and barrier collapses. Lots of attention in cities in the west of Santa Catarina and the west and southwest of Paraná.
As the cyclone deepens on the coast, the wind will blow moderate to strong this Friday in all regions of Rio Grande do Sul with gusts, on average, of 50 km/h to 80 km/h, but which can reach 80 km/h to 100 km /h, isolatedly superior, in Lagoa dos Patos. The worst of the wind between this Friday and Saturday will occur in the coastal strip, where gusts between 70 km/h and 90 km/h are expected, but in some parts of the coast they could reach around 100 km/h or more. There is a risk of falling trees, poles, lack of electricity and localized roofing.
This Friday, at the beginning of the day, low pressure will be over Rio Grande do Sul and deepens, already with the cyclogenesis process, advancing towards the coast during the day, where it intensifies even more as an extratropical cyclone that will be with its center (B), estimated by the models at up to 995 hPa, very close to the South Coast of Rio Grande do Sul between Chuí and Rio Grande, over the Atlantic Ocean.
On Saturday, the cyclone will be over the Atlantic, still close to the coasts of Rio Grande do Sul and Uruguay at the beginning of the day, even more intense and with pressure projected by several models between 980 hPa and 985 hPa, but over the period the The system moves away from the continent in an East-Southeast direction while a high pressure center with colder air begins to take over southern Brazil.
On Sunday, in turn, the cyclone will already be far from the coast. A mass of drier and colder air covers Rio Grande do Sul at the weekend, associated with a high pressure center (A) that will be positioned over the Rio da Prata during the day.
Therefore, the weather improves and firms up this weekend in Rio Grande do Sul. The sun, which may already appear in some cities in Rio Grande do Sul this Friday, due to the cyclonic circulation that usually brings alternation of sun, clouds and rain, will begin to predominate throughout the weekend.
Although the cyclone will move away over the weekend, both Saturday and Sunday are expected to see intense sea disturbances on the coast. This Friday, the sea could be very rough on the South Coast, in the Hermenegildo and Rio Grande regions. A sea undertow is expected on the coast, as the very intense wind over the ocean, at high seas, of 120 km/h to 150 km/h, will generate a significant swell. Navigation with small boats on the coast and in inland waters such as Lake Guaíba and Lagoa dos Patos is extremely discouraged.
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