Hurricane, from the Carib Indians of the West Indies who called them huracan, probably derived from the Mayan storm god, Hunraken; or the Quiche god of thunder and lightning, hurakan; or other Caribbean Indian terms for evil spirit and big wind. The Spanish modified it to hurricane.

Tropical Cyclones account for approximately 1/8 of the deaths attributed to weather related disasters.

This is what usually happens. An area of thunderstorms develops in the tropics. They can grow higher there than elsewhere in the world because the tropopause, where cloud growth normally ends, is higher. As the thunderstorms get taller, the group develops a spin from the Coriolis Force and more hot, moist air is brought in from the surface. This replaces the air which is flowing upward and then outward as it reaches the high altitude winds. This warm moist air gives the system more energy. The cycle keeps going until there is no more hot air available to fuel the Tropical Cyclone.

It has been speculated that Tropical Cyclones occur only in the hot season because in the winter, the jet stream transfers temperatures and energy throughout the globe. But in the summer, the jet is so weak that another way is needed to keep Earth's energy budget balanced. So we have the Tropical Cyclone.

A Tropical Cyclone has different names throughout its average 12 day life cycle, depending on the wind speed.

• Tropical Disturbance - A slight rotary circulation with no strong winds. A common occurrence in the tropics. There are several different types of Tropical Disturbances: an easterly wave, a West African Disturbance Line (WADL), a disturbance in the Intertropical Convergence Zone (ITCZ), a trough or cold Low in the upper troposphere, or an old polar front. So if you hear any one of these terms on the evening weather show, you know something is brewing in the tropics that could develop into a major storm.
• Tropical Depression - A rotary counterclockwise circulation with the highest sustained wind of 39 miles per hour. It is at this point the hurricane people recognize it as a possible threat and give it a strange name like TD4 (Tropical Depression number four).
• Tropical Storm - A distinct rotary counterclockwise circulation with sustained wind of 39 miles per hour to 73 miles per hour. Now the Hurricane Center in Miami, FL, gives it a real name, like TROPICAL STORM EMILY. The eye becomes visible.
• Hurricane - Strong, very pronounced counterclockwise rotary circulation with winds of 74 miles per hour and higher. The eye is very pronounced.

• A HURRICANE WATCH means there is a possible hurricane threat to the area within 24 to 36 hours.
• A HURRICANE WARNING means hurricane conditions are expected to affect the area in less than 24 hours. Take immediate precautions.

HURRICANES...AND HOW THEY FORM

There are no other storms like hurricanes on earth. Views of hurricanes from satellites located thousands of miles above the earth show how unique these powerful, tightly coiled weather systems are.

WHAT IS A HURRICANE?

A hurricane is a type of tropical cyclone - the general term for all circulating weather systems (counterclockwise in the Northern Hemisphere) over tropical waters.

Hurricanes are products of the tropical ocean and atmosphere. Powered by heat from the sea, they are steered by the easterly trade winds and the temperate westerlies as well as by their own ferocious energy. Around their core, winds grow with great velocity, generating violent seas. Moving ashore, they sweep the ocean inward while spawning tornadoes and producing torrential rains and floods. Each year on average, ten tropical storms (of which six become hurricanes) develop over the Atlantic Ocean, Caribbean Sea, or Gulf of Mexico. Many of these remain over the ocean. However, about five hurricanes strike the United States coastline every 3 years. Of these five, two will be major hurricanes (category 3 or greater on the Saffir-Simpson Hurricane Scale).

SAFFIR-SIMPSON HURRICANE SCALE

1: 74-95 mph winds, minimal damage ex: Florence 1988 (LA), Charly 1988 (NC)

2: 96-110 mph winds, moderate damage ex: Kate 1985 (FL Panhandle), Bob 1991 (RI)

3: 111-130 mph winds, extensive damage ex: Alicia 1983 (N TX), Emily 1993 (NC Outer Banks)

4: 131-155 mph winds, extreme damage ex: Andrew 1992 (S FL), Hugo 1989 (SC)

5: >156 mph winds, catastrophic damage ex: Camille 1969 (LA/MS), Labor Day Hurricane 1935 (FL Keys)

A Category 1 hurricane is characterized by slight damage to shrubbery, trees and unanchored mobile homes. Low-lying coastal roads are inundated and piers suffer minor damage.

In a Category 2 hurricane, shrubbery and trees undergo considerable damage, and some trees are blown down; however, there is no major construction damage. Low-lying roads along the coast are cut off by rising water several hours before the hurricane center arrives. Evacuation of coastal residents is required.

Serious flooding occurs along the coast in a Category 3 hurricane. Leaves are torn from trees and large trees are uprooted. Small buildings suffer some structural damage. Large buildings along the coast are battered by waves and floating debris, and coastal roads are flooded up to five hours before the arrival of the storm eye. Evacuation of residents within several blocks of the shoreline is required.

Category 4 hurricanes blow over shrubs, trees and signs. Mobile homes are demolished, and there is extensive damage to roofing materials, windows and doors on more substantial buildings. Beaches are eroded extensively. Residents within two miles of the coast should be evacuated.

In a Category 5 hurricane, residents that live up to ten miles from the shore could be evacuated. Windows and doors suffer extensive damage. Some buildings are completely destroyed.

GILBERT in September, 1988, CAMILLE, in August, 1969, and the "Great Hurricane of 1935" that inundated parts of the Florida Keys are the only three storms that have been classified as a Category 5. So far.

Now that we know this, we can assume that major hurricanes are rather rare and obviously coastal residents from Texas to Maine can live contentedly without ever experiencing the total destruction of a Category 5 hurricane. But just between you and me, do not be too content, as none of our Gulf and east coastal areas are immune. Be prepared, stay alert and become Hurricanewise.

Timely warnings have greatly diminished hurricane fatalities in the United States. In spite of this, property damage continues to mount. There is little we can do about the hurricanes themselves. However, NOAA's National Hurricane Center and National Weather Service field offices team up with other Federal, state, and local agencies; rescue and relief organizations; the private sector; and the news media in a huge warning and preparedness effort.

BREEDING GROUNDS

In the eastern Pacific, hurricanes begin forming by mid-May, while in the Atlantic, Caribbean, and Gulf of Mexico, hurricane development starts in June. For the United States, the peak hurricane threat exists from mid-August to late October although the official hurricane season extends through November. Over other parts of the world, such as the western Pacific, hurricanes can occur year-round.

Developing hurricanes gather heat and energy through contact with warm ocean waters. The addition of moisture by evaporation from the sea surface powers them like giant heat engines.

Early in the Atlantic Tropical Cyclone season, which runs from June 1st through November 30th, the Caribbean Sea and Gulf of Mexico are the general formation zones. By July and August, the center of creation shifts eastward to the west coast of Africa, and then drifts slowly westward again. By September, the breeding ground extends from the Bahamas to the Lesser Antilles. From there, it shifts further westward and back to the original formation zones, the Caribbean and Gulf of Mexico. Do not forget, in meteorology, everything is "usually."

Hurricanes rarely bother our west coast or Hawaii, so we sit smugly thinking only about Atlantic Tropical Cyclones. Out of sight, out of mind. Actually, the incidence of these storms in the Pacific is three times what it is in the Atlantic. Their hurricane season runs from May 15th to November 30th. Of course, the Pacific is much larger than the Atlantic, so the storms have more room to move. Also, the Pacific Ocean has a larger expanse of warm water for the Tropical Cyclones to feed on. The reason they rarely hit our west coast is because the flow of water in that part of the ocean brings in colder water, which has a tendency to kill Tropical Cyclones, rather than promote them.

Pacific Tropical Cyclones can form off the west coast of Mexico and the easterly trade winds push the storm west, away from the California coast. Most of these storms perish at sea, but some travel the entire width of the Pacific. Over the Pacific, the tropical storm season never seems to end; it just slows down during the winter.

Sometimes moisture from Tropical Cyclones along Mexico's west coast gets caught in the westerlies, flowing over Mexico and into our southwest region. Ten inches of rain and more can fall over New Mexico, Kansas, and Iowa. Interesting to be sure.

HURRICANE MOVEMENT

The Greatest Storm on Earth originates in the warm waters near the equator, and generally affects the east coast of large continents. Simply put, air heated by the warm ocean rises, reaches its condensation point and generates a great amount of energy by a process called Heat of Condensation. In fact, the energy from only one storm, if it were possible to convert to electricity, would provide enough to supply the United States for at least a year. It generates 1,000 times the total energy output for the United States.

Tropical Cyclones survive as long as they track through warm waters. When a Tropical Cyclone comes ashore or moves over cold water, it quickly loses its force, and dissipates. Good thing too; imagine 200 miles per hour winds blowing across thousands of miles of land.

Tropical Cyclones do not move on certain tracks like a railroad train, nor do any two move along identical paths. In fact, the track they do follow is not even a straight line. So, long-range forecasting is an exercise in futility. Satellites are nice, and they show where the hurricane is located, pointing out the eye and providing an awesome picture for the television audience. Forecasting the movement is left in the hands of meteorologists. Unfortunately Mother Nature does not listen, or pay attention, to the hurricane advisories.

When the storms do come ashore and lose their force, we tend to forget about them; but that is the time to be on the alert. We ignored HURRICANE AGNES in 1972 before she hit the Susquehanna Valley in Pennsylvania. She held her power and looped back around and hit the Valley again a few days later, producing the rains of the century, like 19" on Harrisburg, PA.

DIANE, in 1955, caused little excitement along the shore points but when moving inland and losing her windy punch, the rains and floods began. Two hundred people perished in Pennsylvania, New York, and New England. Usually Tropical Cyclones do decay rapidly after landfall, but sometimes they do not.

Averages prove there is a scarcity of Tropical Cyclones. During any given year, only two will hit the East Coast and out of an average of 104 Tropical Disturbances building in the Atlantic every year, only ten will reach Tropical Storm stage, with six of these intensifying to hurricane force.

The Pacific Ocean will get about 16 Tropical Storms and Hurricanes. During the 1970's, fewer storms crossed our coast line than in any other decade of the 20th century. Thirty-nine percent of all hurricanes bothering this country affect Florida.

The diameter of a hurricane eye ranges up to 25 miles and the wall cloud around the eye extends up to ten miles high. Passage of the eye can be eerie and can make your blood run cold. If it is approaching from the south, and the winds have reached 120 miles per hour from the east, your whole life might pass before your very eyes. Suddenly, no wind, no noise, no rain, no blowing debris, and maybe the Sun or moon appears to remind us there is always a tomorrow. This is the time for a quick prayer of thanks; then brace yourself again, and collect your wits.

The howling winds return from the west and the trembling begins again. But the good news is you have survived the first half of the storm; it can only get better.

STORM STRUCTURE

The process by which a disturbance forms and subsequently strengthens into a hurricane depends on at least three conditions. Warm waters and moisture are mentioned above. The third condition is a wind pattern near the ocean surface that spirals air inward. Bands of thunderstorms form, allowing the air to warm further and rise higher into the atmosphere. If the winds at these higher levels are relatively light, this structure can remain intact and allow for additional strengthening.

The center, or eye, of a hurricane is relatively calm. The most violent activity takes place in the area immediately around the eye, called the eyewall. At the top of the eyewall (about 50,000 feet), most of the air is propelled outward, increasing the air's upward motion. Some of the air, however, moves inward and sinks into the eye, creating a cloud-free area.

Let's get some things straight:

• The generic name for all these storms is Tropical Cyclone.
• Hurricanes occur in the South Pacific, Eastern North Pacific, the North Atlantic, Gulf of Mexico and the Caribbean.
• In the western portions of the North Pacific these storms are called Typhoons.
• In the Philipines, a Baguio, named for the city that received 46" of rain in 24 hours from a tropical storm in July, 1911.
• Down under, in the Timor Sea and northern Australia, these storms are not called Willy-Nillys, which is the popular belief. They are known as Tropical Cyclones. (A Willy-Nilly is a small dust storm.)
• A Tropical Cyclone also occurs in the Indian Ocean and the Bay of Bengal.

No matter the name, they are still the same old Tropical Cyclone.

STORM SURGE

Storm surge is a large dome of water often 50 to 100 miles wide that sweeps across the coastline near where a hurricane makes landfall. The surge of high water topped by waves is devastating, The stronger the hurricane and the shallower the offshore water, the higher the surge will be. Along the immediate coast, storm surge is the greatest threat to life and property.

THE STORM SURGE

The storm surge is a great dome of water that comes into contact with the coastline near where the hurricane eye makes landfall. It is caused by the low pressure in a storm making the waters underneath rise, maybe by as much as 25' above the normal high tide, and the strong winds which push the surge ahead of the storm. All that extra water pounding into the shore spreads major damage. If the normal astronomical tide is three feet and the storm surge is 18', then the storm tide is 21 feet. The storm surge can occur up to 50 miles on either side of the hurricane eye.

A group of people in a Mississippi apartment complex decided to have a hurricane party during HURRICANE CAMILLE. The apartment complex was destroyed and the sole survivor was a woman who floated out a window on top of the storm surge using a mattress as a life raft. Twelve hours later, she was rescued from a tree 4.5 miles away from her home. This storm surge of 20' had waves of 15' more on top of it.

STORM TIDE

If the storm surge arrives at the same time as the high tide, the water height will be even greater. The storm tide is the combination of the storm surge and the normal astronomical tide.

The hurricane moves ashore. In the above example, a 15-foot surge added to the normal 2-foot tide creates a storm tide of 17 feet. This mound of water, topped by battering waves, moves ashore along an area of the coastline as much as 100 miles wide. The combination of the storm surge, battering waves, and high winds is deadly.

The storm surge claims nine out of every ten hurricane victims. This great dome of water sweeps across the coastline as the storm makes landfall. Spectators, who should not be out there, are caught by the surge as the giant wave carries away everything in its path.

Should a storm roar ashore at time of Spring Tides, the highest tide of the month, the surge gains additional height. The lunar phase, a long shallow ocean floor and a funneling effect caused by a V-shaped bay all contribute to the great death toll suffered when a cyclone hits the Bay of Bengal. In 1789, 20,000 people were lost, 50,000 in 1864, and in 1876 the "bakerganj" delivered a 40' surge and 400,000 people never knew what happened. The ocean has no mercy.

If a storm surge threatens, go inland for 25 miles, or more, as soon as possible. Do not stick around waiting to see what will happen. If something does happen, you will not have time to make a decision.

A great and tragic catastrophe is waiting to happen along our coastlines. Especially at places such as the New Jersey coast and other coastlines, where building has taken place on the Barrier Islands.

New Orleans is a disaster waiting to happen, with the Gulf of Mexico, a large lake close by, and a river running through town. This type of construction has spread from Maine to Texas as we convince each other that we must live closer to the ocean. So it is gonna happen; a mature hurricane will strike at the time of high astronomical tide and the storm surge will inundate everything in its path. And then we will close the barn door.

We talk about evacuation as the answer and it would help, but the Weatherwise will leave the danger area before the storm becomes an immediate threat. Have you been in the traffic jam on bridges and highways during a normal summer Sunday evening as all the weekend travellers are trying to get home from the shore? It backs up for miles, accidents occur and then add to the confusion draw-bridges which open to let boats pass. Even when there is no emergency, the short trip can take hours. Imagine five times the number of people in twice the hurry and everyone in a panic!

STORM TIDE FACTS

Over 6,000 people were killed in the Galveston Hurricane of 1900 - most by the storm tide. Hurricane Camille in 1969 produced a 25-foot storm tide in Mississippi Hurricane Hugo in 1989 generated a 20-foot storm tide in South Carolina.

WINDS

Hurricane-force winds, 74 mph or more, can destroy poorly constructed buildings and mobile homes. Debris, such as signs, roofing material, siding, and small items left outside, become flying missiles in hurricanes. Winds often stay above hurricane strength well inland. Hurricane Hugo (1989) battered Charlotte, North Carolina (which is about 175 miles inland), with gusts to near 100 mph, downing trees and power lines and causing massive disruption.

The greatest threat from the wind is flying debris. Parts of buildings, signs, lawn furniture, roofing and the like fly through the air like rockets and slam into stationary objects with the power of a sledge hammer. The winds are not too dangerous, but the noise is scary.

HEAVY RAINS/FLOODS

Widespread torrential rains often in excess of 6 inches can produce deadly and destructive floods. This is the major threat to areas well inland. Tropical Storm Claudette (1979) brought 45 inches of rain to an area near Alvin, Texas, contributing to more than $600 million* in damage. Long after the winds of Hurricane Diane (1955) subsided, the storm brought floods to Pennsylvania, New York, and New England that contributed to nearly 200 deaths and $4.2 billion* in damage. Hurricane Agnes (1972) fused with another storm system, producing floods in the Northeast United States which contributed to 122 deaths and $6.4 billion* in damage.

* Adjusted to 1990 dollars.

Floods and flash floods caused by torrential downpours are a constant threat during Tropical Cyclones. Up to 15" of rain is common. How about the uncommon? CLAUDETTE on July 25th, 1979, dumped 43" near Alvin, TX. Never take your eyes off these fellows until they enter Europe.

TORNADOES

Hurricanes also produce tornadoes, which add to the hurricane's destructive power. These tornadoes most often occur in thunderstorms embedded in rain bands well away from the center of the hurricane. However, they can also occur near the eyewall.

AREAS AT RISK

COASTAL AREAS AND BARRIER ISLANDS

All Atlantic and Gulf coastal areas are subject to hurricanes or tropical storms. Although rarely struck by hurricanes, parts of the Southwest United States and Pacific Coast suffer heavy rains and floods each year from the remnants of hurricanes spawned off Mexico. Islands, such as Hawaii, Guam, American Samoa, and Puerto Rico, are also subject to hurricanes. During 1993, Guam was battered by five typhoons. Hurricane Iniki struck the island of Kauai, Hawaii, on September 11, 1992, resulting in $1.8 billion damage.

Due to the limited number of evacuation routes, barrier islands are especially vulnerable to hurricanes. People on barrier islands and in vulnerable coastal areas may be asked by local officials to evacuate well in advance of a hurricane landfall. If you are asked to evacuate, do so IMMEDIATELY!

INLAND AREAS

Hurricanes affect inland areas with high winds, floods, and tornadoes. Listen carefully to local authorities to determine what threats you can expect and take the necessary precautions to protect yourself, your family, and your property.

• Camille - August 14-22, 1969: 27 inches of rain in Virginia caused severe flash flooding.
• Agnes - June 14-22, 1972: Devastating floods from North Carolina to New York produced many record-breaking river crests. The storm generated 15 tornadoes in Florida and 2 in Georgia.
• Hugo - September 10-22, 1989: Wind gusts reached nearly 100 mph as far inland as Charlotte, North Carolina. Hugo sustained hurricane-strength winds until shortly after it passed west of Charlotte.
• Andrew - August 16-28, 1992: Damage in the United States is estimated at $25 billion, making Andrew the most expensive hurricane in United States history. Wind gusts in south Florida were estimated to be at least 175 mph.

THE UNITED STATES HURRICANE PROBLEM

POPULATION GROWTH

The United States has a significant hurricane problem. Our shorelines attract large numbers of people. From Maine to Texas, our coastline is filled with new homes, condominium towers, and cities built on sand waiting for the next storm to threaten its residents and their dreams.

There are now some 45 million permanent residents along the hurricane-prone coastline, and the population is still growing. The most rapid growth has been in the sunbelt from Texas through the Carolinas. Florida, where hurricanes are most frequent, leads the Nation in new residents. In addition to the permanent residents, the holiday, weekend, and vacation populations swell in some coastal areas 10- to 100-fold.

A large portion of the coastal areas with high population densities are subject to the inundation from the hurricane's storm surge that historically has caused the greatest loss of life and extreme property damage.

PERCEPTION OF RISK

Over the past several years, the warning system has provided adequate time for people on the barrier islands and the immediate coastline to move inland when hurricanes have threatened. However, it is becoming more difficult to evacuate people from the barrier islands and other coastal areas because roads have not kept pace with the rapid population growth. The problem is further compounded by the fact that 80 to 90 percent of the population now living in hurricane-prone areas have never experienced the core of a "major" hurricane, Many of these people have been through weaker storms, The result is a false impression of a hurricane's damage potential. This often leads to complacency and delayed actions which could result in the loss of many lives.

FREQUENCY OF HURRICANES

During the 70's and 80's, major hurricanes striking the United States were less frequent than the previous three decades. With the tremendous increase in population along the high-risk areas of our shorelines, we may not fare as well in the future. This will be especially true when hurricane activity inevitably returns to the frequencies experienced during the 40's through the 60's. In the final analysis, the only real defense against hurricanes is the informed readiness of your community, your family, and YOU.

SURVEILLANCE AND FORECASTING

SATELLITE

Geostationary satellites orbiting the earth at an altitude of about 22,000 miles above the equator provide imagery both day and night. The satellite imagery helps provide estimates of the location, size, and intensity of a storm and its surrounding environment.

RECONNAISSANCE AIRCRAFT

The U.S. Air Force Reserve provides most of the operational reconnaissance. Pilots fly aircraft into the core of a hurricane to measure wind, pressure, temperature, and humidity as well as to provide an accurate location of the center of the hurricane. The National Oceanic and Atmospheric Administration also flies aircraft into hurricanes to aid scientists in better understanding these storms and to improve forecast capabilities. The NOAA flights also provide operational support as required.

RADAR

When a hurricane gets close to the coast, it is monitored by land-based weather radars. The National Weather Service is currently installing Doppler weather radars across the country which will add new dimensions to hurricane warning capabilities. They will provide detailed information on hurricane wind fields and their changes. Local NWS offices will be able to provide more accurate short-term warnings for floods, tornadoes, and inland high winds.

NATIONAL HURRICANE CENTER MODELS

The National Hurricane Center uses several different numerical computer models to aid in forecasting the path, speed, and strength of hurricanes. Data from weather satellite sensors, reconnaissance aircraft, and other sources are fed into these computer models. The National Hurricane Center also has a computer storm surge model. This model provides guidance on storm surge height and the extent of flooding it will cause.

WHAT TO LISTEN FOR...

NOAA WEATHER RADIO is the best means to receive warnings from the National Weather Service. The National Weather Service continuously broadcasts updated hurricane advisories that can be received by NOAA Weather Radios sold in many stores. The average range is 40 miles, depending on topography. Your National Weather Service recommends purchasing a radio that has both a battery backup and a tone-alert feature which automatically alerts you when a watch or warning is issued.

• TROPICAL STORM WATCH: Tropical Storm conditions are possible in the specified area of the watch, usually within 36 hours.
• TROPICAL STORM WARNING: Tropical Storm conditions are expected in the specified area of the warning, usually within 24 hours.
• HURRICANE WATCH: Hurricane conditions are possible in the specified area of the watch, usually within 36 hours. During a Hurricane Watch, prepare to take immediate action to protect your family and property in case a Hurricane Warning is issued.
• HURRICANE WARNING: Hurricane conditions are expected in the specified area of the warning, usually within 24 hours. Complete all storm preparations and evacuate if directed by local officials.
• SHORT TERM WATCHES AND WARNINGS: These provide detailed information on specific hurricane threats, such as tornadoes, floods, and high winds.

INFORMATION FOR LOCAL DECISION MAKERS

• The PUBLIC ADVISORY issued by the National Hurricane Center provides critical hurricane warning and forecast information.
• The MARINE ADVISORY issued by the National Hurricane Center provides detailed hurricane track and wind field information.
• The TROPICAL CYCLONE UPDATE issued by the National Hurricane Center highlights significant changes in a hurricane that occur between advisories.
• PROBABILITIES OF HURRICANE/TROPICAL STORM CONDITIONS provide a measure of the forecast track accuracy. The probabilities have no relation to tropical cyclone intensity.
• HURRICANE LOCAL STATEMENTS issued by local National Weather Service offices give greater detail on how the storm will impact your area.

All of the above information must be used to make an informed decision on your risk and what actions should be taken. Remember to listen to your local official's recommendations and to NOAA Weather Radio for the latest hurricane information.

Hurricane safety rules