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Brazil Storm Was Bad But NOT Tropical!

By Jesse Ferrell, Meteorologist/Community Director
9/15/2009, 9:40:53 AM

At least two articles, here and here, are saying that a storm made "landfall" in Brazil. To quote from the second source, which shows a satellite picture of a rotating low pressure system over the coast:

"A powerful cyclone with winds raging up to 120 kmph (75 mph) made landfall in the southern Brazilian state of Santa Catarina on Tuesday evening and moved westwards, to the Argentinean border."

This cyclone (the articles claim) was the cause of the tornado that crossed the Argentina/Brazil border last week, as well as flooding at the end of the week. Some incredible pictures from the MetSul Weather Center during this event can be seen throughout this blog entry. CNN says that the tornado had 125 mph winds and over 1 million lost power from last week's storms.


The quote above, of course, brings to mind 2004's Cyclone Catarina, quoted with exactly the same wind speed, hitting the same state in Brazil -- the only tropical storm to ever form in the South Atlantic (so far as anyone knows).

But in this case, there was just a "cyclone" (low-pressure system) that caused the bad weather, originating over land, moving OFFshore (no landfall), and was certainly not tropical. (As's Jim Andrews pointed out, it's late winter in the Southern Hemisphere; "Catarina" hit in March, late summer). This low pressure was a central player in an unusual severe weather situation.

How can we prove this? The synoptic weather maps below, provided by Alexandre Aguiar from MetSul, show the low pressure moving east from land to the ocean over time (maps are every 12 hours from Sept. 6 to Sept. 8 and are available for download in higher resolution here).


Alexandre said in an email "It was a conventional and CONTINENTAL low. No low made landfall. A thermal (warm) low deepened over Northern Argentina prior to the cold front. It was a quasi stationary low over land that deepened and favored the severe weather."

So what of the satellite image the article presented? It may have been stock footage. It is colored like a MODIS image but doesn't appear on their site here or here, and it doesn't match this Infrared image that was found by My Buddy Scott [JessePedia]...



Alexandre went on to talk about the power of the storm:

"Monday, September 7th, 2009, will never be forgotten by many communities in Southern Brazil. In the national holiday for the country’s independence in 1822, an outbreak of severe weather brought damage and destruction with isolated tornadoes, torrential rain, high winds and large hail. The storms were ignited by an intense cold front that rushed to Southern Brazil, where the air was very warm and incredibly unstable. Thunderstorms stability indices were in the roof, according to model analysis that day: Showalter of -8, CAPE near 5.000, Total Totals of 58, K of 47 and Lifted Index of -10. The first severe storms affected late in the morning the Northern part of Uruguay and South Rio Grande do Sul, the southernmost state of Brazil. Bage Airport recorded a gust of 70 knots. In the vicinity of Bage, damages are consistent with tornadoes in many towns. According to the local Civil Defense of Acegua, Brazil, a home water tank was found near 3 miles away of its original location. Hundreds of trees fell along 40 miles of a road connecting Bage to the city of Acegua. In the afternoon, in Central Rio Grande do Sul, large hail damaged over one thousand homes in the city of Itaara. In Northern Rio Grande do Sul, high winds (a tornado was not still ruled out) caused major damages in Victor Graeff.


Later in the day, the storms reached the states of Santa Catarina and Parana. In Guaraciaba, Western Santa Catarina, a tornado partially destroyed the city of Guaraciaba. Four people died. In the other side of the border, ten people died due to a tornado in San Pedro, province of Misiones, in Argentina. MetSul Weather Center believes that it is possible that the same tornado in Argentina caused the damage and the deaths in the Brazilian town of Guaraciaba. Damage in Guaraciaba was severe and even catastrophic in some points of the city. A car was thrown near 40 feet and was found in the middle of a field. Our first estimate points to a F3 tornado.

On Tuesday, September 8th, the storms reached Sao Paulo, Brazil’s largest city and one of the most populated in the world. Heavy rain brought the city to a standstill. Eight people died in high risk areas in slums located in the slopes of hills due to landslides. Brazilian National Weather Service stated Sao Paulo experience the most rainfall in 24 hours in September since records began in 1943 with 80 mm (around 3 inches).

From Wednesday (9th) Saturday (12th) the problem was the rain in Southern Brazil due to a stationary front that was reinforced by a low pressure system that migrated from Northern Argentina to the region. In less than a week, some towns recorded up to 12 inches of rain. Since the beginning of the month, the precipitation reaches 15 inches in some places. And August was vey wet. In just 40 day, some cities in the state of Rio Grande do Sul have already observed 20 inches of rain. The result of so much water was inundation. Several rivers overflowed their banks. Thousand were forced out their homes. The majority of the river began to subside, but forecast models are indicating another round of heavy rain later this week."

Here's a video that's Raychel Harvey-Jones did the day of the tornado:

I thank Alexandre for his detailed information and wish all of the areas affected in South America the best for recovery efforts, which I'm sure are ongoing. You can see even more information on this storm, including weather followups, radar images and newspaper clips, on the MetSul Blog (some of the highest weekly rainfall totals I found there were over 17 inches!)

By the way, I understand that there is a lot of confusion internationally when referring to a "cyclone" (which could mean low pressure, hurricane, or tornado in different languages) but here I see something that is really being misrepresented. Even if this storm would have come from the ocean (a Sou'easter??) according to WikiPedia only a "tropical cyclone" can "make landfall" -- a rule that I almost broke last week (except that considered the East Coast storm tropical so it was still a valid remark).

The views expressed are those of the author and not necessarily those of AccuWeather, Inc. or


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