A typhoon is defined as a tropical cyclone in the western Pacific with high winds (hurricanes are storms with winds more than 75 mph near its center). Typhoons generally track in a westward or northern direction, and occur most frequently in a region of the western Pacific and east Asia that includes the Philippines, Vietnam, Taiwan, southern China, South Korea, southern Japan, Guam, the Marianas Islands and parts of Micronesia. They generally blow themselves out if they travel west of Vietnam or into the interior of China. and do not occur south of the Philippines.
A typhoon is essentially the same thing as a hurricane, which is defined as a strong tropical storm with winds over 75 miles per hour, occurring in the west Atlantic and the eastern Pacific, particularly in southeastern North Americas and the Caribbean. Similar storms in the Indian Ocean are called tropical cyclones; one that strike Australia are called willie willies. Cyclone is also a catch all phrase which describes all low pressure systems over tropical waters and includes typhoons and hurricanes as well All these storms feature super heavy rain as well as high winds.
The word “typhoon” comes from the Cantonese word tai feng. The approach of a typhoon is heralded by large waves, a storm surge, and falling barometric pressure. As it get nearer mountains of cumulus clouds appear and intensifying wind squalls culminate in an on-sweeping wall of dense clouds with furious winds and torrential rain. Describing a South China Sea storm in 1935, one American captain wrote: "A terrible crash was heard! The vessel trembled like an aspen-leaf...with the sea pouring in over the bow, and the topsails shivering like so many rags." Joseph Conrad described the storms in his novels Lord Jim and Typhoon.
The typhoon season lasts from the early summer to early autumn, often coinciding with the monsoon season in Southeast Asia and the wet season in eastern Japan. The main typhoon and hurrican season is from June to November. Sometimes they appear as early as May and as late as December. Storms can be particularly fierce in years of the El Niño. Usually more damage is caused by the heavy rain than by the winds.
Madeleine Nash wrote in Smithsonian magazine, “Hurricanes belong to a broad class of storms known as tropical cyclones, which also occur in the Indian and Pacific oceans. They do not develop spontaneously but grow out of other disturbances. In the Atlantic, most evolve out of "African waves," unstable kinks in the atmosphere that spiral off the West African coast and head toward Central America. Along the way, these atmospheric waves generate ephemeral clusters of thunderstorm-producing clouds that can seed hurricanes. At the same time, hurricanes are much more than collections of thunderstorms writ large; they stand out amid the general chaos of the atmosphere as coherent, long-lasting structures, with cloud towers that soar up to the stratosphere, ten miles above the earth's surface. The rise of warm, moist air through the chimney-like eye pumps energy into the developing storm.” [Source: Madeleine Nash, Smithsonian magazine, September 2006]
On average about 80 tropical cyclones occur annually around the world. Describing a category 5 hurricane, Madeleine Nash wrote in Smithsonian magazine, “As the storm bore down, sustained winds in the eye wall reached 160 miles per hour, with gusts that exceeded 200 miles per hour. The winds lifted up sheet metal roofs and wooden planks, hurling them through the air with lethal force; in some cases, as one writer described, "pounding sheets of sand sheared clothes and even the skin off victims, leaving them clad only in belts and shoes, often with their faces literally sandblasted beyond identification." [Source: Madeleine Nash, Smithsonian magazine, September 2006]
The highest wind ever recorded was at Mount Washington, New Hampshire in 1934: 230 miles hour
Hurricanes and typhoons in the northern hemisphere have an eye and thunderstorm-producing cumulus clouds that spiral out in a clockwise direction from the eye. They eye is 5 to 25 miles wide and is relatively calm, sometimes windless. Strong winds blowing towards the center of the area of extreme low pressure and cirrus streamer clouds radiating east or southeast direction and bent by the Coriolis affect. The most destructive part of the storm is usually the northern, leading side of the storm. The east side of a typhoon generally is more devastating than the west side.
The “eyewall,” an area just beyond the eye, is the region of the most intense winds of all. It is often only a kilometer or so wide but it interacts with the rings of thunderstorms that produce the heaviest winds and rains and its behavior and dynamics are crucial to the behavior of the storm as a whole. The eyewall is shaped by two opposing forces: 1) moist, warm air from inside the eye, which can feed the eyewall, strengthening it; and 2) dry air from outside the eye that can slowly bleed into it, and calm it down.
Air flowing from high pressure to low pressure causes winds. If the difference between high pressure and low pressure is great, intense circulation is generated, causing a powerful storm. As air spirals into a low-pressure zone warm humid air and warm sea surface winds meet and ascend, causing clouds to billow upwards, further lowering air pressure and causing winds to swirl even faster towards the center .
The deflecting action of the Earth’s rotation spins the developing cyclone (counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere). When water in the ascending clouds cools and falls as rain heat energy is produced, which further warms the storm, lowering the pressure and making the storm stronger. The cyclone can continue to strengthen as long it remains over warm water and is not destroyed by vertical wind shear---winds traveling at different speeds at lower and high altitudes---which can cut off the top of a storm breaking up it energy producing engine.
Madeleine Nash wrote in Smithsonian magazine, “Ocean warmth is essential---hurricanes do not readily form over waters cooler than about 79 degrees Fahrenheit---but the right temperature is not enough. Atmospheric conditions, such as dry air wafting off the Sahara, can cause hurricanes---along with their weaker cousins, tropical storms and depressions---to falter, weaken and die. Vertical wind shear---the difference between wind speed and direction near the ocean's surface and at 40,000 feet---is another formidable foe. [Source: Madeleine Nash, Smithsonian magazine, September 2006]
Storms can change very quickly. In 2005 Hurricane Wilma jumped to a Category 5 storm in less than 24 hours. 1935 Labor Day Hurricane in the Florida Keys, Madeleine Nash wrote in Smithsonian magazine, “exploded from a Category 1 to a Category 5 hurricane in 40 hours, about the amount of time an evacuation of the Keys might take today. As the storm bore down, sustained winds in the eye wall reached 160 miles per hour, with gusts that exceeded 200 miles per hour. The winds lifted up sheet metal roofs and wooden planks, hurling them through the air with lethal force; in some cases, as one writer described, "pounding sheets of sand sheared clothes and even the skin off victims, leaving them clad only in belts and shoes, often with their faces literally sandblasted beyond identification." [Source: Madeleine Nash, Smithsonian magazine, September 2006]
Types of Typhoons
Supertyphoons are very destructive. They are defined as typhoons with winds over 150 miles per hour. Such storms produce horizontal rain and can measure several hundred miles across, cover thousands of square miles and reach an altitude of almost ten miles tall. The largest storm on record, the 1979 typhoon Tip, produced gale force across a 650 mile area.
The power generated by a major hurricane is said to be equal to half a million nuclear bombs. The power of an average storm is said to be equal to 1.5 trillion watts---the equivalent to about half the world’s entire electrical generating capacity.
Atlantic storms are defined as: 1) Tropical Depression; 2) Tropical storm (less than 74 miles per hour); 3) Category One (between 74 and 95 miles per hour); 4) Category Two (between 95 and 110 miles per hour); 3) Category Three (between 111 and 130 miles per hour); Category Four (between 131 and 155 miles per hour); and Category Four (more than 155 miles per hour).
In Asia, different countries have different systems for identifying typhoons. Some countries such as Japan use numbers. Others use names.
Birth of Hurricanes and Typhoons
Marc Kaufman wrote in the Washington Post: “Twenty-one days before Hurricane Katrina made landfall at New Orleans last summer, a relatively small "wave" of turbulent air emerged from western Africa and headed out to sea. Over the ocean, that trough of low atmospheric pressure began to shrink, and it was further diminished by a mass of dry and dusty air from a large Saharan dust storm that blew offshore at about the same time. Over the eastern and central Atlantic, the dusty cloud mingled with the tropical wave and helped keep it weak and diffuse. But somewhere out over the Atlantic, that same atmospheric wave joined up with one or more other tropical depressions coming off Africa. Within days, the relatively small turbulence grew into the tropical cyclone that, as it crossed the ocean, became the hurricane that would devastate the Gulf Coast two weeks later. [Source: Marc Kaufman, Washington Post, August 7, 2006]
“Although many hurricanes that reach the United States are born as tropical depressions in the waters off Africa, little is known about why some peter out and others become monster hurricanes on the other side of the ocean. This is increasingly important information to have, and so a team of researchers from NASA and the National Oceanic and Atmospheric Administration will spend the next two months off the African coast trying to find the answer. "These waves are pretty innocuous -- lines of heavy rain with some thunderstorms," said Jeffrey Halverson, a NASA mission scientist and professor at the University of Maryland in Baltimore County. "But about 10 percent change character as they move to sea and get rotations and start building up power. That's the big mystery: Where does the spin come from?" [Ibid]
“About 60 waves every year come off West Africa in the late summer and head toward the Caribbean and North America, carried by trade winds. Most of the time, these weather patterns -- called African easterly waves because they form over the Darfur region of Sudan or Ethiopia in East Africa -- stretch 1,200 to 1,500 miles and last three to four days before they dissipate, unless they grow into something bigger. They get their initial power and instability from the difference in temperature between the very hot Sahara Desert air and the substantially cooler air along the coast of the Gulf of Guinea. [Ibid]
Playing an important role is “the Saharan air layer that forms over the desert during the late spring, summer and early fall, and generally moves out over the tropical Atlantic Ocean. Its very hot and dry air, strong winds and airborne dust are thought to inhibit cyclone development. There is some evidence that the dust makes it more difficult for rain to form, but that factor is currently not considered in hurricane computer models. [Ibid]
Typhoons develop in an area of the tropical Pacific at a latitude between 10 and 20 degrees north. They usually begin as westward-drifting “waves” of clouds drawn into an area of low pressure around the Caroline Islands of Micronesia (between Hawaii and the Philippines in the Pacific) and grow into westward-moving tropical depressions.
As the clouds advance across the warm water they pick up energy as the water evaporates. At a critical point the clouds develop into a vortex of air that rotates in a counter-clockwise direction because of the Coriolis effect (see above). The water temperatures generally have to be above 80̊F for all this to occur. The warmer the sea surface temperature are, and the more warm, moist air there is, the stronger the storm will be.
A number of things have to come together for a typhoon to form. Among them are the presence of an initial low-pressure system that pulls the air to a particular spot in the ocean; the Coriolis effect spinning the air in a vortex; difference in wind speed in the upper and lower parts of the atmosphere that create horizontal “shear forces”; and the presence of cold air 10 miles up in the atmosphere.
Factors that influence typhoon development include water temperatures and rainfall amounts in the Pacific; El Niño (which produces high-level winds that blow the top of typhoon clouds); and stratospheric jet-streams wind patterns. Scientist also believe that typhoons can be influenced by seemingly unrelated things like the atmospheric temperatures above Singapore.
According to a study by scientists at the University College London high sea temperatures are the most reliable indicator of increased typhoon and hurricane activity. The reasoning is that warmer seas cause more water to evaporate. As the water rises, latent heat is released which provides the energy for low pressure cell to develop into a hurricane.
Typhoons are self-feeding and self-reinforcing events fueled by: 1) evaporated water that releases energy when it condenses back into water; and 2) driving rapid updrafts that cause water to evaporate from the ocean, forming self-sustaining vortexes of swirling clouds and high winds. They dynamics of all this---especially of forces than can cause a storm to suddenly intensify---remain little understood. Among the clues that a storm is about to intensify are the presence of chimney clouds called hot towers that can reach as high as 11 milies into the atmosphere.
Rapidly moving air over warm water absorbs unusually large amount of water vapor through evaporation. As the air converge at the center of the storm, it rises. As the air rises, it cools and some of the water vapor condenses into droplets. That process release energy in the form of “heat cf condensation.” [Source: Washington Post, ✳]
The heat is released into a column of air that is already warmer than the air outside the storm. There can be as much as a 30̊F difference between air in the eyewall and air at the same altitude outside the storm. The heat dissipates slowly, in part because the air is contained in a rotating system. Meanwhile, the newly released reheated air continues to rise, eventually losing more moisture and condensation and releasing more heat. In this way a large and powerful typhoon can influence its environment in such a way as to allow the storm to get even bigger and stronger.✳
When the rising air exits from the system, sometimes as high as 50,000 feet above the sea surface, it is cold and relatively dry. As it departs more air is pulled in at the bottom of the storm, continuing the cycle. The energy from the warm water beneath the storm is vital to keeping the whole thing going. When a typhoon goes over cool water or land it tends to fall apart. High upper atmosphere winds are also great typhoon killers. They can sometimes sheer the tops off of a typhoon and cause it to suddenly collapse.
Hurricanes maintain and gain strength over the sea and lose strength when the go overland. Islands are often so small they little effect. The intensity of a storm is also related to its interaction with the sea. Warm water at the top of the ocean provides fuel. As the storm spins, it churns the water beneath it, bringing cooler water from the depths. The cooler water acts as a brake to slow the engine down. Some of the most intense storms are feed by warm water that is over a hundreds of meters deep and the breaking action of cooler water does not occur. Large waves can also slow a storm down by blunting the winds that created them.
Damage from Typhoons
Typhoons can cause millions or even billions of dollars in damage. Buildings slide down hillsides; valleys flood; villages disappear under landslides and mud slides; roads and bridges are washed away; crops become waterlogged, or are blown over or uprooted, or covered in mud. Destruction levels can be particularly high when a storm stalls and strong, driving rains persist for hours or even days, or when the storm slams into mountains, producing particularly large amounts of rain. Some typhoons are so powerful they blow plankton and small sea creatures into the sky, where they float around on clouds.
Usually much more damage and death is caused by rains than winds. People die from being hit by flying debris or falling trees or crushed in collapsed building but are more likely they die from drowning in flooded rivers or from suffocating under rain-induced mud slides and landslides. Most victims from the really deadly storms die from storm surges---masses of ocean water that are pushed forward by the winds---that can penetrate several miles inland. The surges are particularly deadly if they occur at high tide.
Typhoons often do the most damage on low coral islands which are sometimes inundated with waves that can reach a height of 30 meters at sea and storms surge that sweep water across the entire island, annihilating every tree and hut in their path. Modern buildings and houses with cinder block walls and metal roofs are usually strong enough to withstand the winds of strong typhoons but thatched-roof huts and shanties on the other hand are easily blown over or crushed by falling trees. Palm trees also blow over pretty because they don't have a deep root system.
Long term damage from typhoons includes sickness and starvation as water supplies become contaminated; cholera and dysentery spread; poisonous snakes are flooded out of their dens; crops and stored food are damaged; and transportation routes used to bring in relief supplies are disrupted or destroyed. Over the longer term fields and agricultural land may be is destroyed; rivers may be rerouted; factories washed away; infrastructure is damaged and people migrate out. In poor countries there is inevitably not enough money to fix everything.
Hurricanes account for nine of the 10 costliest U.S. natural disasters since 1989, with Hurricane Katrina at the top of the list with $125 billion in damage and 1,833 deaths, according to the U.S. Federal Emergency Management Agency and the National Oceanic and Atmospheric Administration.
Coastal Changes Caused by Hurricanes and Typhoons
Describing changes to the northern Gulf coast caused by hurricanes there, Cain Burdeau of Associated Press wrote: “Everywhere scientists look, they see disrupted patterns in and along the Gulf of Mexico. Coral reefs, flocks of sea birds, crab- and shrimp-filled meadows and dune-crowned beaches were wrapped up in -- and altered by -- the force of hurricanes Katrina, Rita, and Dennis. ''Nothing's been like this," said Abby Sallenger, a US Geological Survey oceanographer, during a recent flight over the northern Gulf Coast to study shoreline changes. [Source: Cain Burdeau, Associated Press, February 5, 2006]
For him, the changes are mind-boggling: Some barrier islands are nearly gone; on others, beaches are scattered like bags of dropped flour. Hurricanes have been kneading the Gulf Coast like putty for eons, carving out inlets and bays, creating beaches and altering plant and animal life -- but up to now, the natural world has largely been able to rebound. Trees, marine life ,and shoreline features tourists and anglers enjoyed in recent years were largely the same types as those 17th century buccaneers and explorers encountered.
But scientists say the future could be different. Nature might not be able to rebound so quickly. The reason: the human factor. ''Natural systems are resilient and bounce back," said Susan Cutter, a geographer with the University of South Carolina. ''The problem is when we try to control nature, rather than letting her do what she does." The seas are rising, the planet is getting hotter ,and commercial and residential development is snowballing. Add those factors to a predicted increase in nasty hurricanes and what results is a recipe for potentially serious natural degradation, some say.
Surveys of the washed out Chandeleur Islands, an arc of barrier islands off the coast of Louisiana, found nesting grounds for brown pelicans, royal terns, sandwich terns, and black skimmers gone.''Hopefully the birds will be resilient enough to move to other areas," said Tom Hess, a biologist with the Louisiana Department of Wildlife and Fisheries. ''We will have to see." Salt water spread by Hurricanes Katrina and Rita killed marsh grasses across the Louisiana coast, leaving little left to eat for Louisiana's most hunted bird -- the duck. ''Most of the marsh where that salt water sat for a long time looks dead. It looks like it is does extremely late in the winter and you've had several extreme frosts," said Robert Helm, a state waterfowl biologist. ''Where we found birds, they seemed to be concentrated in the habitat that was not impacted by the storm."
A lot of things are happening under the water, too. With their towering waves, hurricanes move huge volumes of mud and sediment on the ocean bottom, burying clam and oyster beds and seagrass meadows where crabs, shrimps and fish hide and feed. Can the sea plants spring back? ''It depends on the light penetration, how deep they are buried, and factors like that," said John Dindo, a marine scientist and assistant director of the Dauphin Island Sea Lab in Alabama.
Farther out, where the continental shelf drops off, the wild seas kicked up by the hurricanes damaged the Gulf's coral reefs.After Rita's 30-plus-foot waves, surveys of the coral at the Flower Garden Banks National Marine Sanctuary 100 miles off the coast of Louisiana and Texas showed damage to about 5 percent of the reef. Brain and star coral was toppled and smashed into other coral heads. About 3 feet of sand was dispersed on sand flats in the reef where trigger fish and queen conch burrow and nest.
Areas Hit by Typhoons
Most typhoons usually track north and first strike places like Guam, Saipan, Taiwan and Okinawa and then either move northward into Japan or Korea or move westward into the Philippines, Vietnam, or China. Because the Caroline Islands of Micronesia are breeding grounds for typhoons they rarely get hit by fully developed storms. Typhoons usually pass north of Palau.
The island of Okinawa lies right in the heart of Typhoon alley. The islands there get hit by an average of seven storms a year, some of them with winds exceeding 190 miles per hour. in the old days, fisherman's families there kept their finances in the name of the wife because fisherman often went out to sea and didn't come back.
Taiwan also gets hot quite a bit. After typhoons Taiwanese fishermen can sometimes be seen on the shore collecting washed up herring-like fish with chopsticks.
Typhoon Warning System
Typhoons frequently occur in Taiwan, which has its own storm warning system that alerts Taiwanese citizens of impending storms over the TV and radio. The first warnings are a 1) Storm Advisory, which warns a storm could strike within 48 hours; a 2) Sea Warning, which projects a storm will be within 60 miles of the shore within 24 hours; and a 3) Land warning, which projects a storm will hit land within eight hours.
Condition 24: destructive winds can be expected in 24 hours. At this stage Taiwanese are advised to fill their gas tanks, make sure they have plenty of flashlight batteries and candles and put away loose boards or other items that can be picked up by the wind and injure people.
Condition 12: destructive winds can hit within 6 hours. At this time Taiwanese are told to move valuables upstairs, and fill the bathtub and containers with water.
Condition 6: destructive winds can hit within 3 hours. Taiwanese are told to turn up refrigerator to maximum cold and try not to open it; unplug nonessential appliances; stay indoors; use the phone only for emergencies; do not travel; and tape large windows that might be exposed to heavy winds.
Emergency Alert: Destructive winds and rain are occurring over the island. Stay indoors, move furniture away from the windows, roll up rugs and place them on furniture if there is a possibility of flooding. If power goes out use refrigerator as little as possible.
Some scientists say the best place to seek shelter in a storm is a concrete parking garage which is unlikely to collapse because it solidly built and winds blow through it rather than push on it. Moreover the winds that blow through it subside once they are inside the structure
Naming Hurricanes and Hurricanes That Become Typhoons
Since 1950 American forecasters have identified storms using an alphabetical system of names. Beginning in 1953 those names were only female ones, but in 1979, at the urging of women's groups, male names were added. These days meteorologists plan ahead, compiling six years' worth of names--three male and three female for each letter of the alphabet except Q, U, X, Y, and Z (leaving 21 letters usable for names). Every six years the lists of names repeat, with the names of particularly devastating storms removed from the list. With the number of storms increasing some worry that the day will come soon when the number of storms in a given year will exceed the number of letters available for names. [Source: Whitney Dangerfield, National Geographic, Geographica. October 2005]
In the Pacific ocean a hurricane is a tropical cyclone on the east side of the international date line and a typhoon is such a storm on the west side. In recent years an increasing number of hurricanes have been crossing the international date line in the Pacific Ocean and turning into typhoons. Typhoon No. 12, for example, which struck Japan in September 2006, began on the east side of the international date line and turned into a hurricane there and crossed to the west side, when it was a category 5 storm with 270 kph winds, to became a typhoon. Typhoon no. 12 was the 16th hurricane to become a typhoon since the Japan Meteorological Agency began its monitoring operation in 1951. Before 1990 there were only six cases of this happening---two in the 1950s, one each in the 1960s and 70s, and two in the 1980s. In the 1990s there were seven such hurricanes that became typhoons and three between 2000 and 2006. [Source: Yomiuri Shimbun, September 2006]
World's Worst Recorded 20th Century Cyclones, Hurricanes, Typhoons and Other Storms (number of dead): 1) Bangladesh, Nov. 13, 1970 (300,000); 2) Bangladesh, Apr. 30, 1991 (139,000); 3) H. Bengal, India, Oct. 15-16, 1942 (40,000); 4) Bangladesh, June 1-2, 1965 (30,000); 5) Bangladesh, May 28-29, 1963 (22,000); 6) Bangladesh, May 11-12, (17,000); 7) Hong Kong, Sept. 18, 1906 (10,000); 8) Bangladesh, Dec. 15, 1965 (10,000); 9) Bangladesh, May 25, 1985 (10,000); 10) Caribbean, Hurricane Flora, Oct 4-8, 1963 (6,000); hurricane in Galveston, TX, Aug-Sept, 1900 (6,000).
Improving Coastal Defenses Against Hurricanes and Typhoons
Deborah Zabarenko of Reuters wrote: “Global warming is expected to cause more severe hurricanes, and that means U.S. communities will need new tactics to minimize storm damage, emergency preparedness have experts said. These tactics range from restoring wetlands -- which may actually slow down approaching storms -- to making homes and other structures better able to withstand hurricanes to organizing finances so more can be spent on prevention, the panel of experts said. [Source: Deborah Zabarenko, Reuters, August 27, 2007]
Wetlands, which used to be drained as a matter of course in the United States, provide flood control by absorbing excess water during storms, filter pollutants before they enter streams, lakes and oceans and protect coastal areas from erosion, according to a 2006 Government Accountability Office report.
Image Sources: Wikimedia Commons
Text Sources: New York Times, Washington Post, Los Angeles Times, Times of London, The Guardian, National Geographic, Smithsonian magazine, The New Yorker, Time, Newsweek, Reuters, AP, AFP, Wall Street Journal, The Atlantic Monthly, The Economist, Global Viewpoint (Christian Science Monitor), Foreign Policy, Wikipedia, BBC, CNN, NBC News, Fox News and various books and other publications.
© 2008 Jeffrey Hays
Last updated November 2012