Hurricanes Essay, Research Paper
The Coriolis Effect
Hurricanes have been an active weather phenomenon throughout history. Thanks to our modern equipment, they are easy to track, yet still difficult to predict. Their destructive force causes millions of dollars in damage each time they hit land. We use male and female names to name them. They begin as many storm clouds over warm water and begin to form a tropical storm when enough of them gather. The rotating earth sets the storms in motion. The Coriolis Effect, which is the apparent deviation of an object, greatly influences the path of a hurricane, and must be taken into effect when trying to predict its path.
Hurricanes are known around the world for their destructive and deadly force. They are migratory tropical cyclones that originate over oceans in areas near the Equator, and consist of high-velocity winds blowing circularly around a low-pressure center, known as the eye. We will look further into the specific details regarding the composition of the hurricane later.
The word “hurricane” comes from a tribe of people who lived in Central America thousands of years ago. They believed in a god who caused violent storms that raged upon the land from the sea. The god’s name was Hurakan, and his storms were called hurakans. After European explorers arrived in the Americas, they changed the name to hurricane, which is the term we use today. Hurricanes, like all weather, are not just a modern dilemma. They have brought disaster to people in all eras, even well known historical figures. For instance Christopher Columbus, on his first voyage to America, founded the first non-Indian town on the island of Hispaniola, which he named Isabella after his queen. Why isn’t this tremendously monumental and unique settlement ever discussed extensively in history books? Because less than a year after it was settled, it was totally destroyed by a hurricane and almost all records and artifacts from the island were lost. Ten years later Christopher Columbus was again thwarted by a hurricane. He had just set sail from Central America in 1503 when a hurricane moved in from the Atlantic, and he had no choice but to sail through it. He credits God for allowing his rickety old ships to successfully navigate through the storm. Here is an except from his diary regarding his crews’ journey into the storm:
Eyes never beheld the seas so high, angry, and covered by foam. The wind not only prevented our progress, but offered no opportunity to run behind any headland for shelter?Never did the sky look more terrible?The lightning broke forth with such violence that each time I wondered if it had carried off my spars and sails; the flashes came with such fury and frightfulness that we all thought the ships would be blasted. All this time the water never ceased to fall from the sky?1
In 1607 the colonists founded the city of Jamestown and hurricanes hadn’t been reported since 1570, when part of the Spanish Armada was sunk by a hurricane. Many people weren’t had forgotten they even existed. Two years after Jamestown was
officially settled, a fleet of ships was headed to the colony from England when they were caught in a violent hurricane. When the few survivors staggered into the harbor on the storm-beaten ships, they told horror stories that spread throughout the world, and the hurricane was once again feared as in the days of Hurakan. It was this fear that inspired Shakespeare to write The Tempest, his famous play about a violent hurricane. One last historical account of a hurricane is an ironic story that involves the Pilgrims. Most people know that the Pilgrims fled England from religious persecution and landed at Plymouth Rock, Massachusetts. But records show that their destination was actually Virginia, where they would reside in Jamestown before founding their own colony. It was an encounter with a hurricane at sea that sent them off course and landed them in Massachusetts.
The first study of a hurricane was done completely by accident. In 1680, an English pirate named William Dampier was caught in a hurricane while pirating around the Atlantic. His crew lost control of his ship and were forced to just let the hurricane blow them for hundreds of miles. When the storm had passed, Dampier checked his coordinates and found that he was within a mile of where he had been when the ship first encountered the hurricane, therefore concluding that hurricane winds move in a gigantic circle. He called hurricanes “vast whirlwinds.”1
To consider how a hurricane is formed, one must first understand the five ingredients that determine whether a simple tropical storm will mature into a full-blown hurricane or just fizzle out. Those ingredients include: ocean water, the heat of the sun, air, wind, and the spin of the earth. Though many scientists disagree regarding the life of hurricanes, they almost all agree on their births.
Hurricanes form when the heat of the sun warms some ocean water. The evaporating water forms a cloud or column of wet, warm air that moves upward. As this warm, moist air rises, more air rushes in to replace it. This air is also heated and moistened by the warm ocean surface. It begins to rise and form clouds, heating the air around it. Eventually, a large mass of warm, moist air with rain clouds is formed over the ocean. Because the air is warm, it expands. It becomes less dense and lighter, and forms an area
of low pressure. More air near the ocean surface now rushes in. However, this air doesn’t just flow straight in. It spirals in like water going down a bathtub drain.appendix a This spiral, or spinning motion, is caused by the rotation of the earth. The air goes faster and faster as it spirals inward.appendix b Then it rises in the clouds to form an eye and wall clouds. The whole storm, now spinning like a top, is carried across the ocean by the wind. Finally, when it moves over land or cold water, it loses its fuel source (warm ocean) and dies.
Hurricanes are extremely large, sometimes well over 400 miles in diameter. The winds that spiral in toward the eye can reach up to 75 miles an hour, while at the eye the sky is clear and the air is calm. Hurricanes are very erratic in nature and therefore it is extremely hard to predict their paths. Perhaps the greatest modern-day example of the behaviour of hurricanes is Hurricane Elena3. Elena was born off the western coast of Africa on August 22, 1985 and only classified as a tropical disturbance, which means that the winds are moving less than 20 miles per hour. It rapidly moved across the Atlantic in less than a week, and by the time it reached Cuba it was a tropical storm, the winds moving over 60 miles per hour. Two days later, on August 29, Elena was upgraded to hurricane status, with winds exceeding 130 miles per hour. Meteorologists were stunned by Elena’s unpredictability. Let’s see if you can forecast her path of destruction. (see exercise 1)
It goes without saying that hurricanes hold a lot of energy. It is estimated that if all the latent heat released during a hurricane of average size could be harnessed for use, it could supply the entire United States with enough electricity for six months.4 Oddly enough, the damage from hurricanes rarely comes from the millions of gallons of rain that they release. Flood waters from huge waves and the consequential flooding, along with the high winds that ravage the landscape, cause one hundred times more damage than the rain. And in the bayou region of Louisiana, residents are more concerned with poisonous snakes that wash up and nest in crevices and holes, and then come out after the storm disoriented and violent, than the water and wind.
Before we look at our final topic, we need to look at how hurricanes are named. In the late nineteenth century and early twentieth century, hurricanes were named simply by their location. (ie. Hurricane Texas, Hurricane Louisiana, etc.) After World War Two,
only female names were used, but after 1978, both male and female names were used. The first storm of the year begins with the letter ‘A’ and each subsequent storm follows in alphabetical order, alternating between male and female. A name is given to a storm only when it reaches tropical storm strength (when winds are above 60 miles per hour). After a storm receives the impressive category 3 rating, which means winds are blowing at over 115 miles per hour, the name is retired for ten years before it can return to the list. Here are some of the names on the year 2000 list: Aletta, Bud, Carlotta, Daniel, Emilia, Fabio, John, Zeke? for the Eastern Pacific storms, and Alberto, Beryl, Chris, Keith, and William?for the North Atlantic storms.
Now we come to the Coriolis effect, a factor crucial for hurricane forecasters. Named after the French physicist Gaspard de Coriolis, the Coriolis effect is the force or acceleration acting on the motion of bodies in a rotating system of reference.2 To put it a little more simply, an object moving above the earth in a northerly or southerly direction will be deflected in relation to the rotation of the earth. This deflection is clockwise in the Northern Hemisphere, and counterclockwise in the Southern Hemisphere.
To better understand this principal, lets look at a scenario involving a merry-go-round. Say you and a friend wanted to play catch on a flat, round merry-go-round. When the ride is still, obviously you can throw the ball to each other with no problem. But let’s say that the ride started rotating counterclockwise, as the earth does as viewed from the North Pole. When you throw the ball and it’s in the air, the merry-go-round is spinning beneath the ball, and for you and your friend, the ball appears to veer to the right, like this:
It sounds so interesting to us the way it all works, and fun to observe, but imagine the pressure on scientists earlier this century who were in charge of launching missiles! Before they could be programmed on where to strike, those in charge of launching them had to carefully factor in the Coriolis effect, or else the missile would land completely off target.
But what does the Coriolis effect have to do with hurricanes? Hopefully you’ve figured it out by now. The hurricane, nothing more than a high-pressure mass of clouds and strong winds, resides above the earth while the earth spins beneath it. So, like the ball on the merry-go-round, or a missile, a meteorologist has to take into careful consideration the Coriolis effect when trying to predict the path of a hurricane, because the direction it’s heading will rotate with the Earth, and a new location will be in it’s path.
Other aspects of life affected by the Coriolis effect include aircraft flights and NASA space-shuttle launches. Also, if it wasn’t for the friction between your car tires and the road while travelling on a highway, the Coriolis effect would pull your car 1500 feet to the right for every 10 miles traveled!4
So what are the practical applications after a study on hurricanes? Fortunately for those of us who live in Michigan, hurricanes don’t affect us like they do the coastal states. In the past, the only two things that hurricanes have done to Michigan are 1) swirl a mass of rain-laden clouds in our direction and gave us a day or two of steady rain, and 2) prevented masses of high-pressure to move eastward, giving us days of calm and clear weather. With the advent of Doppler radar, hurricanes are very easy to track, and the National Weather Service does a good job of issuing warnings and watches, giving people ample time to leave town until the storm is over or board up their house. But no matter how well you can track a hurricane, or even predict its path, constructing buildings to withstand winds in excess of 200 miles an hour (Hurricane Camille, 1969), flood waters, and torrential rains, still remains a very formidable task.