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Rare South Atlantic Hurricane Heads Toward Brazil
jellisky writes "An unprecendented sort of weather event has been occuring recently, without much fanfare at all. A tropical cyclone in the south Atlantic is slowly drifting toward Brazil. The southern Atlantic ocean isn't exactly a hurricane hotbed, as pointed out by National Hurricane Center forecaster Jack Beven, "We know there hasn't been a hurricane in that area since at least the satellite era, the mid-60s at the minimum." The storm is a small one, though, but has estimated winds near minimal hurricane strength (74-95 mph). It's quite an interesting sight, perfect for piquing the weather curiousity that many of us have."
Here's a nicer image of the cyclone.
Aesthetically more pleasing. However, the OSEI image didn't crop the edges of the storm system, and the increased amount of land mass visible allows easier identification of where the storm is occuring in relation to the South American coast. In addition, the infrared information contained in the OSEI image makes it far more easy to distinguish between relatively warm, low-lying clouds (yellowish) and the cold tops of the cloud towers near the eye of the storm (in white).
"I'm so moist I'm sticking to the leather." -Kermit the Frog on The Late Late Show
Tropical cyclones with maximum sustained surface winds of less than 17 m/s (34 kt, 39 mph) are called "tropical depressions". (This is not to be confused with the condition mid-latitude people get during a long, cold and grey winter wishing they could be closer to the equator ;-)) Once the tropical cyclone reaches winds of at least 17 m/s they are typically called a "tropical storm" and assigned a name. If winds reach 33 m/s (64 kt, 74 mph)), then they are called: a "hurricane" (the North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline, or the South Pacific Ocean east of 160E); a "typhoon" (the Northwest Pacific Ocean west of the dateline); a "severe tropical cyclone" (the Southwest Pacific Ocean west of 160E or Southeast Indian Ocean east of 90E); a "severe cyclonic storm" (the North Indian Ocean); and a "tropical cyclone" (the Southwest Indian Ocean) (Neumann 1993).
In any case, most models do not predict large warming of the equatorial band, partially because evaporation over tropical oceans keeps the atmosphere from heating. Of course, this increased evaporation leads to increased latent heat, which is a possible cause of extreme weather.
Having said that, one extreme event does not proof of climate change make. Climate change is about long term trends, not short term weather. If we see more South Atlantic hurricanes over the next decade, then there would be an indication that they could be a result of climate change.
Then we could look for the proximate cause: increased latent heat, ocean temperature patterns, change in winds, salinity changes, all of the above concurrent or consecutive, whatever. Then we would ask, is this change something we would expect from human induced change, eg increased greenhouse gas forcing or aerosols or something else.
Subject: G7) Why doesn't the South Atlantic Ocean experience tropical cyclones?
Though many people might speculate that the sea surface temperatures are too cold, the primary reasons that the South Atlantic Ocean gets no tropical cyclones are that the tropospheric (near surface to 200mb) vertical wind shear is much too strong and there is typically no inter-tropical convergence zone (ITCZ) over the ocean (Gray 1968). Without an ITCZ to provide synoptic vorticity and convergence (i.e. large scale spin and thunderstorm activity) as well as having strong wind shear, it becomes very difficult to nearly impossible to have genesis of tropical cyclones.
However, in rare occasions it may be possible to have tropical cyclones form in the South Atlantic. In McAdie and Rappaport (1991), the US National Hurricane Center documented the occurrence of a strong tropical depression/weak tropical storm that formed off the coast of Congo in mid-April 1991. The storm lasted about five days and drifted toward the west-southwest into the central South Atlantic. So far, there has not been a systematic study as to the conditions that accompanied this rare event.
Pasted from the local oglobo.globo.com, free reg. required.
Ciclone Catarina ganha forca e deve atingir Santa Catarina neste domingo
ClicRBS
CBN
RIO - Batizado de Catarina, o ciclone extratropical que se formou a 440 quilometros da costa sul do pais ganhou forca durante a madrugada deste sabado e deve chegar ao continente na madrugada deste domingo, se for mantido este ritmo de deslocamento.
O ciclone, que tem ventos de 118 a 152 quilometros por hora, deve entrar no continente brasileiro entre Itajai, no litoral norte catarinense, e a Foz do Prata, no litoral gaucho, atingindo principalmente as praias de mar aberto. Especialistas preveem ventos de 70 km/h, podendo chegar a 170 km/h em alto mar.
E possivel que o fenomeno afete areas no interior catarinense. Meteorologistas alertam, porem, que nao ha razao para panico. Os efeitos causados pelo ciclone extratropical seriam chuva, vento forte e ressaca no mar. De acordo com a previsao do Centro de Hidrografia da Marinha, as ondas deverao chegar a tres metros de altura no litoral norte de Santa Catarina ate Cabo Frio, no Rio de Janeiro. Em mar aberto, as ondas poderao atingir quatro metros de altura.
Em Santa Catarina, a Defesa Civil e Policia Rodoviaria Federal mantem equipes em plantao permanente atendendo pelo telefone 191. O ciclone que ocorre no litoral e um fenomeno inedito no Atlantico Sul.
Nas imagens de satelite, o ciclone extratropical, com caracteristicas tropicais, e muito parecido com um furacao - o tipo especifico de ciclone que se abate sobre o Oceano Atlantico Norte, o Mar do Caribe, o Golfo do Mexico e o Oceano Pacifico Leste, ao Norte do Equador.
- Esse ciclone e incomum porque se desprendeu do restante da frente fria. E a primeira vez que eu vejo um ciclone extratropical perto do Brasil tao concentrado assim - disse Francisco de Assis Diniz, chefe do Centro Nacional de Previsao do Instituto Nacional de Meteorologia, surpreso com a imagem.
1. I first found out about the storm on Weather Underground.
;)
2. Dvorak Source
3. CNN's 1st page on it. 4. CNN's follow-up page on it.
*. Hats off to the person that beat me to a first post.
Life is irony, and nothing ever goes as planned.
here's another copy of the original study with a slightly improved .pdf conversion:
g e. pdf
http://www.ems.org/climate/pentagon_climatechan