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Another active day in Argentina yesterday! PDF Print E-mail
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Written by Reed Timmer   
Wednesday, 25 November 2009 09:12

vispampaSupercells exploded once again northwest of Buenos Aires, Argentina yesterday, which seems to be a hot spot of late.  An overshooting top of the strongest storm is clearly evident on the satellite image at right, courtesy of Matias Emanuel Bertolotti, also a meteorology student at the University of Buenos Aires.  Matias' website is http://www.weatherar.com, where you can find more interesting information on Argentina tornadoes.  One thing I've noticed while watching these South American tornado outbreaks unfold is that they always seem cellular in nature, with a lack of the forced lines of convection we get here so often in the U.S. Great Plains.  My thinking here is that Argentina does not have the massive Mexican Plateau to their west, which is the main source of warm air at the 850 to 700 mb cap level here in the U.S.  When the capping inversion is too strong, frontal boundaries often force linear convection above the cap level, which is not conducive for tornadoes.  In Argentina, capping inversions seem to be rarely strong enough to limit surface based convection, thus the mode is often cellular in nature.  What do our Argentinian readers think about this???

 

 

 

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0 #1 t-o-r-n-a-d-ogirl91 2009-11-25 16:15
Gosh Reed you catch them no matter where their at and I love it :P Dominate Reed
 
 
0 #2 ernani 2009-11-26 00:42
Part 1:
Hello Reed. I am a reader from Brazil (meteorologist, with a PhD from OU where I used to chase wx with Bob Conzemius; do you know him?). In South America we do not a have a very efficient source for an elevate mixed layer that could lead to those capping inversions. The Bolivian Plateau (a candidate for such a source) is too far north of the region where we get the best ingredients for severe convection.
 
 
0 #3 ernani 2009-11-26 00:42
Part 2:
So, in short, we have a very steep terrain to the west, and not the gentle slope found on the North American Plains. This explains, at least in part, the less frequent observation of capped environments for severe convection. Still, we can get "loaded-gun" soundings occasionally. You can find one such example from southern Brazil in this article from the 22nd AMS SLS Conference (http://ams.confex.com/ams/11aram22sls/techprogram/paper_81745.htm).
 
 
0 #4 ernani 2009-11-26 00:44
Part 3:
Another interesting distinction is the lack of a (true) persistent dry-line in northern Argentina. Because the air mass from the Atacama desert is separated (by the Andes) from the moist air of central South America, we do not get those extreme north-south oriented moisture gradients of the typical north american dry line.

BTW, have fun with our SH tornadic hodographs! I have some of them if you want to take a look. :^)
 
 
0 #5 ernani 2009-11-26 00:51
Finally, yesterday (Nov 25) an isolated severe thunderstorm hit a small town in northwestern Rio Grande do Sul state (southern Brazil) producing significant wind damage. The local civil defense team claims that it was a tornado, but I am not entirely convinced of that as yet. In any case, the satellite imagery shows a very strong isolated cell over that region, as shown in http://pyata.cptec.inpe.br/repositorio1/goes10/web/ams_realcada_alta/2009/11/S11615583_200911251115.jpg
 

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