What is a Hypercane?
Meteorological worst case scenario tells story of a hurricane from hell.
If you thought hurricane Katrina was quite a whopper, professor Kerry Emanuel and his computers at MIT’s Atmosphere, Oceans and Climate Program will teach you otherwise.
His worst case scenario looks something like this: winds of over 600 miles an hour (approaching the speed of sound) whip around the center, water vapor, sea spray and storm debris are catapulted into the atmosphere, punching a hole in the stratosphere 20 miles above Earth’s surface. Central pressure would drop to 200 Millibars. Its super-gale-force winds would flatten forests and toss boulders. A 60-foot storm surge would flood nearby shores. The water vapor and debris could remain suspended high in the atmosphere for years, disrupting the climate and eating at Earth’s protective ozone layer.
It gets worse. Once this super-hurricane has formed, it begins to move away, loose some strength. But a second super-hurricane might form over the same area, followed by a third and forth, until a whole chain of hurricanes and superhurricanes are flattening everything on the surface of the earth.
But fortunately Emanuel is also quick to point out that we shouldn’t expect any of these hyper-hurricanes, or hypercanes, any time soon off our coasts. The circumstances that could lead to such a whopper do not occur easily; Emanuel’s calculations postulate that parts of the ocean would have to warm up to at least 100 degrees. Only the impact of a large asteroid hitting the tropical ocean or a massive undersea volcano could generate such intense heating.
Learning From the Past
This is not to say that such a hypercane, or several of them, might have thundered over earth in the past. Emanuel and his colleagues theorize that asteroid-triggered hypercanes may have contributed to global extinctions. Paleotempestology, a novel branch of meteorology, attempts to clear this up. By analyzing the chemistry of tropical coral reefs for clues about the salinity and temperature of the water, the “fingerprints” of past hurricanes can be found, dating back thousands of years.
The same principle also applies for rivers and lakes. For example, on the bottom of the Hudson River murky sediments and huge natural reefs, made entirely of oyster shells, give evidence of a massive hurricane pre-dating the Great Pyramids. With the amassed data, even cycles in hurricane recurrence could be determined. Sediment cores collected from Lake Shelby in coastal Alabama for instance, revealed that Category 4 and 5 hurricanes struck the area about every 600 years. Another such whopper can be expected anytime soon.
Even with all our computers and knowledge, no one knows for sure how hurricanes get started. Detailing only what we know today would take up several pages, and there is a lot we don’t know. But meteorologists agree on the basic recipe: ocean water 80 degrees or warmer, super humid air, and a bunch of storms with thunderheads. Some assembly still required. “Hurricanes are an accident of nature,” Emanuel says. “Even if all the conditions are right, and they often are in the tropical ocean, hurricanes don’t happen by themselves. They literally need to be triggered.”
Genesis is one of the great enigmas for those who study hurricanes. There is still a lot of research to be done until we can fully understand how hurricanes are born. But we should consider ourselves lucky; compared to the knowledge we had in the fifties and sixties when hurricane research began to rev, our present knowledge is quite advanced, which is good.
At least we can fairly gauge their limitations. It is the friction exerted by the sea on swirling winds that sets the breaks, and in our present climate the worst possible hurricane would have “only” winds of over 200 mph. Thankfully most cyclones don’t live up to that potential, although Katrina came close.
There are also “borders” to where hurricanes can exist. A hurricane needs regions that are thermodynamically able to support its demands for energy, and those remain mostly close to the equator, both in the tropical Atlantic and tropical pacific. That too is good.
Yet a hypercane wouldn’t care about these “borders” once active. The heat engine would just run away and friction would no longer be able to keep up. The hypercane might shrink and loose some of its initial intensity, but hold easily at over 300 mph while grinding down the surface. This would also be the beginning of the hypercane chain as mentioned above, and the end of every living thing on Earth.
So how real is the threat? Will we see a hypercane form for the next season? Fortunately, the answer is no. Unless some meteorite drops in anytime soon, or a gigantic underwater volcano coughs up, we are safe from hypercanes. But superhurricanes of over 200 mph, such one as Katrina aspired to be, are a real threat. And taking into account that a normal hurricane too can hightail at high speed out of its “borders” before dissipating, such cities as Boston, New York, and Tokyo are in potential peril. Meteorologists all agree that it is not a matter of “if” a lusty hurricane might hit one of these cities–but rather a “when.”
And that is bad.