Every year, heat, moisture, and wind in the warm seas north and south of the equator combine to form nature’s most powerful storm. Whether you call it a hurricane, typhoon, or tropical cyclone, its vast swirl of clouds and clear central eye are instantly recognizable on satellite pictures. You may actually have been through one or more in your lifetime, especially if you live near the coast in hurricane-prone regions.
These complex storms hold extreme records—for example, lowest pressure ever recorded (870 mb, Typhoon Tip, 1969); most monetary damage from a single storm ($140 billion in damage, 1926 Great Miami Hurricane, normalized to 2005 [Katrina comes in third on this list]); highest coastal storm surge (42 to 48 feet, Tropical Cyclone Mahina in Bathurst Bay, Australia, 1899)—but other important features are not covered by the media very often. Here are four facts about hurricanes that you might not have known before.
♦ Life on Earth would be worse without hurricanes
The shape of Earth’s orbit around the Sun and the tilt of our planet’s axis guarantee that most of the Sun’s heat energy arrives at and close to the equator. This solar heat evaporates water from the sea surface. A tropical depression can form, and if other factors are right, it will turn into a tropical storm and ultimately a hurricane, now “running” off a new source of heat, that released by condensation of water droplets into rain.
A hurricane, in this sense, is a heat engine. As it travels along and curves away from the equator, it transfers some of the Sun’s heat energy to parts of the planet that would otherwise be quite cool. In this way, hurricanes moderate temperature extremes around the world.
They also transfer a huge amount of tropical moisture up into the middle latitudes. This can make the difference between a normal summer season and a drought. Too much of a good thing, though, can cause devastating floods.
In Australia, life itself depends on the hurricanes (called tropical cyclones there). These systems travel into the arid inner region of the continent, where the reproductive cycle of kangaroos depends on the cooler temperatures and better feeding conditions their rains bring to what otherwise would be a terrible desert.
♦ The internal mechanics of hurricanes are not well understood
Geoscientists have developed ways to study hurricanes in great detail over the years with satellites and other technology. This has often raised as many questions as it has answered.
They have discovered, for instance, that stronger hurricanes, which usually have a very well-developed central area of clearing called the eye, will recycle the cloud wall that surrounds the eye. Forecasters look for this eyewall replacement process, which lasts for several hours as the existing wall falls apart and a new one is built, because it weakens the hurricane somewhat and also expands the wind field. However, they don’t know for sure what causes it or when it will happen.
Experts are also unable to explain why a very few of the more intense hurricanes become annular. Annular hurricanes lose all or most of their spiral rain bands and also develop a central eye that is much larger than usual, giving them the appearance of a ring, or annulus, on satellite views. They have formed in the Atlantic and East Pacific ocean basins but are extremely rare, which is a good thing. These hurricanes weaken much more slowly than ordinary hurricanes, and they are less susceptible to the steering factors in the atmosphere, which makes them more unpredictable and therefore more dangerous.
We humans don’t own the patent on long-distance connections; Earth has been doing it for a very long time.
You probably have heard of El Niño, an annual phenomenon in which the central and east-central Pacific Ocean surface around the equator gets a little warmer than usual; every three to five years, the reverse happens, La Niña, when the same area of the Pacific gets cooler than usual. However, did you know that these events in the Pacific determine how many hurricanes will form in the Atlantic that season?
This teleconnection happens because temperature changes over so much water in the Pacific influence tropical rainfall amounts everywhere from Indonesia to South America, which in turn has an impact on tropical weather worldwide.
El Niño and La Niña also affect the trade winds. Scientists believe that an El Niño weakens surface winds and strengthens upper-level winds over the areas of the Atlantic where hurricanes develop, creating less than ideal conditions and reducing the number of hurricanes that season, while exactly the opposite happens during a La Niña, when there are more hurricanes and storms. The Australian floods of 2010-2011, for example, happened during a La Niña.
♦ Accurate portrayals of hurricanes onstage and in the movies
In late July 1609, the “Sea Venture,” a ship filled with 150 colonists bound for Jamestown, Virginia, was caught in what probably was a hurricane and was blown off course. The desperate captain beached his ship on what turned out to be the island of Bermuda, saving everyone’s life, although the “Sea Venture” was a total loss. Eyewitness accounts from survivors eventually got back to London, where they were heard by a playwright, William Shakespeare, who decided to incorporate the tale into his next play, “The Tempest,” which opens with a shipwreck on Bermuda.
Stage managers were undoubtedly skillful back then, but Globe Theater audiences still needed a lot of imagination to see the storm that Shakespeare’s characters were caught in. The technology of dramatic presentation developed over the centuries, and by 1937, film maker John Ford (who was also an experienced sailor) was able to bring this impressive storm to the screen credibly in “The Hurricane,” his story of love and racism in Polynesia.
Ford prepares his audience for the big storm by adding almost subliminal details in scenes just before it, like the drop in pressure as the hurricane approaches and the arrival of lesser storm-force winds ahead of the hurricane’s very intense core (he draws the viewer’s attention to a wind gauge). By the time the extreme winds and huge storm surge, topped with battering waves, reach the island, viewers are fully prepared to believe this is real, not a movie illusion.
Even today, the accuracy of Ford’s portrayal of a major hurricane’s destructive landfall is remarkable. However, for safety and technological reasons, he couldn’t film his characters out at sea and struggling against the huge waves and fierce winds. This had to await the advent of modern special effects.
In 2000, “The Perfect Storm,” based on the real-life sinking of the “Andrea Gail” in the nor’easter of late October 1991, finally brought all aspects of a hurricane to the screen, including the experiences of some characters who fell into the water amidst 100-foot waves (an incredible wave height to many meteorologists, but probably close to reality, according to buoy measurements near where the “Andrea Gail” actually went down). It’s not hype—a viewer really can feel a little seasick at times during this movie.
While technically a nor’easter, the real “Perfect Storm” absorbed the remnants of Hurricane Grace, and is famous among meteorologists for the way it ended: it turned into another hurricane! Tropical weather experts decided not to give that hurricane a name, as it would be confusing to the public, who already knew the storm as the “Halloween Nor’easter” (the “Perfect Storm” label for it came later on). Therefore, this has also gone down in history as the “Unnamed Hurricane.”
The tropical cyclones that we call hurricanes have many roles in our lives. Their extreme behavior fascinates us and inspires us to tell tales of courage and danger. They show the long-distance connections that exist among ocean basins across the planet. Despite all of our technology and intensive study, there are still important things about hurricanes that we have yet to understand, and we do need to know everything we possibly can about them, for without hurricanes, our lives and those of many other living things would be much more difficult, if not impossible.
Sources and more information:
Australian Broadcasting Corporation (2000). “Eye of the Storm: Southern Exposure.” Retrieved on February 24, 2011, from http://www.abc.net.au/storm/exposure/default.htm
Atlantic Oceanographic and Meteorological Laboratory (June 1, 2010). “Tropical Cyclone Records, Frequently Asked Questions.” Retrieved February 27, 2011, from http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqE.html
National Climatic Data Center (NOAA, NESDIS), United States Department of Commerce. “The Perfect Storm, October 1991.” Retrieved on March 2, 2011, from http://www.ncdc.noaa.gov/oa/satellite/satelliteseye/cyclones/pfctstorm91/pfctstorm.html
United States National Weather Service, Climate Prediction Center (December 19, 2005). “Frequently Asked Questions about El Niño and La Niña.” Retrieved on March 4, 2011, from http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/ensostuff/ensofaq.shtml
Peter Dailey and Joana Dima (August 6, 2007). “Global Teleconnections.” Retrieved on March 4, 2011, from http://www.air-worldwide.com/publicationsitem.aspx?id=14534