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Sou'wester Hits Brazil With Storm Surge, Waves

By Jesse Ferrell, Meteorologist/Community Director
4/10/2010, 5:10:50 AM

I wanted to draw your attention to an article and video on about the continuing bad weather in Brazil. This is something that I brought to the attention of our News Team yesterday and they did a great job reporting on it. Rio de Janeiro lost at least 170 people in a flood early this week when a cold front caused heavy upsloping rain, to the tune of 15 inches. This caused major landslides and flooding, leading to the death toll. The Washington Post says that this disaster's death toll will likely pass the massive flood in 1966 there which killed 250, and that over $207 million in aid has been requested.

This week, as if they needed something else to worry about, what I'm calling a "Sou'wester" (the Southern Hemisphere equivalent of a Nor'easter) developed. These storms aren't rare off the Brazilian coast, but they are not usually that far north, and the positioning is causing a storm surge and waves to 15 feet at Rio. Check out this video showing waves crashing onto the airport runway.


In order to better understand the situation down there, I interviewed Alexandre Alexandre Aguiar, who works for the METSUL Meteorological Center in Brazil (and has a lot of impressive maps & photos on their blog, which is in Portuguese). Here is his explanation of the bad weather:

"The extreme rainfall – near 400 mm in some areas of the city of Rio de Janeiro in just 24 hours last Monday and Tuesday – was caused by a cold front followed by an intense and far-reaching cold air mass for this time of the year. The topography of Rio de Janeiro, a city between the sea and the mountains, favors extreme rainfall events when there is moisture advection coming from the sea. Please pay attention to the high SST anomalies right in the coast of Rio at this moment. Rio was also affected by extreme rainfall with a high death toll also in 1966, 1967, 1971, 1988 and 1996."


"An extratropical cyclone with cold advection – similar to the Nor’easter - formed in the South Atlantic and has been favoring the storm surge along the coast of Rio de Janeiro. The devil is in the details. Well, extratropical cyclones are common in the South Atlantic, but usually they form along the coast of Argentina and in the Plata region. This system originated much to the North, around 27S/28S of latitude, and favored the storm surge in the coasts of Sao Paulo and Rio. Usually, storm surges affect mainly the Southern coast of Brazil (Rio Grande do Sul and Santa Catarina), but if the cyclones is very deep the surge may reach even the Southeast region (Sao Paulo and Rio) and in extreme cases the Northeast shore of the country. As this system developed much to the North than usual, the surge didn’t have a impact here in the South, but was a direct hit for Sao Paulo and mainly Rio."

"Please see the photo of the storm surge at the today’s front page of Correio do Povo, a Brazilian paper based here in Porto Alegre that has the weather services from MetSul. Be free to reproduce it with the credit to Correio do Povo/Newseum."


The image above shows the analysis of waves yesterday as estimated by the WaveWatch computer forecast model.

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