Cold front advances through southern Brazil with rain and storms

Cold front advances through southern Brazil this Tuesday (14) with rain and localized storms of wind and hail. Areas that had a Monday with sun, clouds and heat will have rain, while locations that have experienced a rainy start to the week will experience a gradual decrease in instability followed by an improvement in the weather and the ingress of a cold air mass.

Intense lightning storm marked the beginning of the day in Santana do Livramento | Fabian Ribeiro Leal

This Monday night, strong areas of instability generated by the very hot air from the Midwest advance towards the Center of Rio Grande do Sul, the valleys and Greater Porto Alegre with risk of heavy or torrential rain and risk of isolated storms of wind and hail with many rays. Therefore, the Capital and the metropolitan region may again experience intense rain with lightning and risk of storms after a truce in the late afternoon. Other nuclei of intense instability move to the Northwest of Rio Grande do Sul and the North of the State, in addition to the West of Santa Catarina and Paraná.

In Rio Grande do Sul, Tuesday is still unstable. The cold front still brings rain to part of the state with rain and storms. Rain throughout the day is concentrated in the Northern Half with high volumes in many cities and is accompanied by isolated thunderstorms and strong winds and hail. Cities like Erechim, Passo Fundo, Carazinho, Lagoa Vermelha. Cruz Alta, Ijuí and Bom Jesus may experience heavy to torrential rain with high volumes. Porto Alegre must still have many clouds with periods of rain and that can occur in the form of temporary strong showers, but the volumes will be smaller than today’s and the weather tends to settle between the end of the day and the beginning of Wednesday.

In the west and south of Rio Grande do Sul, the day has many clouds and chances of rain and drizzle at different points, but with low volumes and with a tendency for instability to cease, especially in the second half of the day, with the entry of cooler and drier air. The cold air enters with wind and the temperature declines in most regions with a feeling of cold at night, when the temperature can drop to 13ºC in Santa Maria and 10ºC in cities in the South and on the Uruguayan border.

Cold front causes rain and storms also in Santa Catarina

The weather changes in much of Santa Catarina this Tuesday. Instability areas already bring rain and the possibility of isolated storms tonight in the West and Midwest, but during the course of Tuesday instability takes over the entire Santa Catarina state with rain. Rain will not be heavy in all areas, but isolated spots can have high volumes associated with heavy or torrential showers.

Rain projected by the WRF model in 72 hours between 9 am on Monday and 9 am on Thursday

When encountering very hot air over Santa Catarina, the cold front must cause localized storms that in some points can be strong to severe with the risk of hail and windstorms, not ruling out very isolated occurrences of severe wind with damage. The rain will still come with lightning and thunderstorms. In the fourth, part of Santa Catarina may still have rain, but irregular and more concentrated in the North and Northeast of Santa Catarina, close to Paraná.

Front will bring very irregular rain in Paraná

The high volumes of rain observed in Rio Grande do Sul will not be repeated in Paranã with the arrival of the cold front. The Southwest and West of Paraná already have rain and risk of storms located this night due to the very hot air and the approach of the front, but when arriving in Paraná, the front will bring very poorly distributed rain.

Rain projected by the ICON model in 72 hours between 9 am on Monday and 9 am on Thursday

The sun still appears with clouds this Tuesday in different points of Paraná, but cloudiness increases throughout the day and the weather is unstable in most regions of the state. It just so happens that the rain will not reach all points and will be very irregular with strong showers in localized sectors and zero precipitation in some municipalities. Because of the very hot air, isolated wind and hail storms are not out of the question.

Monday was rain, storms and heat in southern Brazil

Much of Rio Grande do Sul registered a Monday marked by very unstable weather. It rained heavily in several regions and, as expected, the highest volumes occurred in parts of the West, Center, South and areas of the East of Rio Grande do Sul.

Those accumulated until the end of the afternoon of this Monday were 121 mm in Jaguarão, 90 mm in Arroio Grande, 82 mm in Encruzilhada do Sul, 78 mm in Canguçu, 69 mm in Camaquã, 66 mm in Dom Pedrito, 61 mm in Pedro Osório and in Pelotas, 59 mm in Rosário do Sul, 58 mm in Caçapava do Sul, 57 mm in Viamão, 55 mm in Cachoeira do Sul and Alvorada, 54 mm in Porto Alegre, and 50 mm in Venâncio Aires.

The rain was accompanied by many thunderstorms with high incidence of lightning. There were also strong wind gusts that reached 80 km/h in Quaraí. New and intense areas of instability with heavy to intense rain and storms formed in the late afternoon in the Midwest and advanced to the East of Rio Grande do Sul and the Northern Half.

The instability of the second was associated with a low pressure center that interacted with very hot air transported by jet stream (wind) at low atmospheric levels originated in Bolivia and descended to the south of Brazil. Hot air operated as “fuel” (energy) for storms.

It was the wind current with hot air that made the sun appear very hot in the northwest of Rio Grande do Sul today before the late afternoon and evening rain with maximums of 35ºC in São Luiz Gonzaga, 35.9ºC in Santa Rosa and 36 ,8ºC in Porto Xavier.

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In Santa Catarina, the “jet” brought a north wind above 100 km/h in the Planalto Sul and 37ºC in the west of the state. The west of Paraná hit 38ºC. In Asuncion, Paraguay, the 40°C maximum was the highest ever recorded on a September 13, surpassing the previous daily record of 1994.