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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.
We had the tail end of a hurricane from baja hit southern California about 2 years ago... a very rare event.
It didn't do a whole lot of damage; many areas get 80-90mph Santa Ana winds occasionally.
Nothing to see here; Move along.
Oh, but I think that's what makes them so interesting though... The more we know about these storms (their patterns, forces behind them, etc.), the more we can do to be better prepared for them -- potentially saving people's lives that would otherwise be lost.
huzzah
Over the last year there have been several unusual hurricane events. The first recorded hurricane in the Atlantic to occur in April was in 2003, along with the first recorded hurricane in December, both breaking long-standing records. This one however is most unusual because of the weather patterns in that part of the world. While they have most of the necessary conditions (warm water, weather systems) the prevailing winds blow from west to east (as opposed to east to west for the North Atlantic tropics), usually tearing systems that could develop into shreads.
This becomes a problem because unlike areas that are used to hurricanes (US, Carribbean, Pacific, Australia, Madagascar) the Brazilians have no experience with tropical systems, so they have no way of knowing what to expect. Having lived through 16 of them (including Betsy in 1965, Camille in 1969 and Andrew in 1992) all I can say is that anyone living in the potential landfall area might want to consider going inland a ways.
A good site to look at is the Naval Research Labs Monterey hurricane page located here:
http://www.nrlmry.navy.mil/tc_pages/tc_home.html
It lists all of the systems they are following, along with a very good collection of satellite images.
Maybe it's one of the first signs that this prediction may be accurate.
And, as the article says, Bush thinks Global Warmin is a hoax. Typical.
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Roses are #FF0000, Violets are #0000FF, find / -name '*base*' |xargs chown -R us && mv zig greatjustice
Most of the South Atlantic is actually cooler than average, so it seems unlikely that global warming is to blame.
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.
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.