Hypercanes

Discovery Communications, 1998

Kerry Emanuel describes the worst hurricane that could ever happen: Winds whip around its center at 500 miles an hour. Water vapor, sea spray and storm debris are catapulted into the atmosphere, punching a hole in the stratosphere 20 miles above the Earth's surface. If this meteorologist's nightmare ever made landfall, 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 away at Earth's protective ozone layer.

Emanuel calls this a "hypercane."

Don't expect one to be brewing any time soon, however. These hurricanes from hell are a figment of Emanuel's computer models. A professor at MIT's atmosphere, oceans and climate program, Emanuel studies the physics of hurricanes, placing him among an elite group of scientists. He flies into these ferocious tropical storms and measures their physical properties. On land, he deconstructs their machinery using computer models, and digs into their geologic past -- all to understand what makes these whopper storms tick.

No one knows for sure how hurricanes get started. The ingredients for cooking one up still remain a mystery. A basic recipe: ocean water 80 degrees or warmer, super humid air, and a bunch of storms with thunderheads. Some assembly still required. "Hurricanes are accidents 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. In 1991, Emanuel flew a research plane into some cloud clusters off the coast of Mexico to see which ones became hurricanes and which ones didn't. During those flights, Emanuel witnessed the birth of Hurricane Guillermo, a classic hurricane and one of the best studied pre-hurricanes.

Will we ever witness a hurricane as mighty as the ones depicted in Emanuel's computers? It's unlikely, even in the most dire global warming scenario, according to Emanuel. To create such a monster, 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. It might have happened at least once in our past, though. Emanuel and his colleagues theorize that asteroid-triggered hypercanes may have contributed to massive global extinctions millions of years ago.

In our present climate, the worst possible hurricane would have winds of 200 mph. Thankfully most cyclones don't live up to that potential, although Hurricane Andrew came close. By the time it hit Florida in August 1992, it had sustained winds of 145 mph. When at sea, Andrew barely made it to hurricane status, which is defined by a wind speed of 74 mph or greater. Within a day or two, its intensity had shot up. It surprised everyone.