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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.
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
Global warming is just that - a warming, on average, of the globe.
The fact that the majority of the South Atlantic is cooler than average could reflect any one of a number of causes, one of the most likely of which is a warming of the Antarctic leading to increased melting of the icecap, thus releasing lots of cold water into the South Atlantic.
Looking at the chart, this seems plausible, as the concentration of colder water is away from the continental shelf of South America, and appears to skirt around the South Atlantic islands (notice the finger of yellow / orange sticking out from the coast of Argentina).
Cyclone formation is driven by temperature gradients, rather than average temperature, and the fact that the (normally slightly warmer) water on the continental shelf is warmer than usual, whereas the deepwater areas are colder, leads to the conclusion that the temperature gradient is much higher than usual.
So it's not surprising that a cyclone has formed, and the anomalous temperature gradients are perfectly consistent with global warming.
One thing from the map - I'd love to be in a boat off Namibia right now, watching the dolphins and whales - that extra cold water will be full of food, and it'll be a bumper autumn's fishing all along the South-West coast of Africa.
oh brave new world, that has such people in it!
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.
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.