What is a Hurricane?
A hurricane is a huge tropical storm. Tremendous
amounts of energy get sucked up into swirling winds. These giant wheels of
wind can cause serious damage, especially if they reach land. The high tides
and churned- up water in a hurricane cause damage too, and sometimes deaths.
This storm formed over the northwest Pacific Ocean, so it is called a typhoon.
These particular types of storms are called different names depending upon
where they form. Storms that form over the Atlantic Ocean are called hurricanes.
If they form over the northwest Pacific Ocean, they’re called typhoons.
In the South Pacific and the Indian Oceans, they’re called cyclones.
The scientific name is the same all over the world- tropical cyclone.
In the Atlantic Ocean, hurricane season begins
June 1 and lasts until November 30. In the northeast Pacific, the season is
a little longer. It goes from May 15 through November 30. Most hurricanes
occur in the hottest months—July through September. In the South Pacific,
which is in the Southern Hemisphere, the season is the other half of the year
- November through April.
How Do Hurricanes Form?
Hurricanes only form from warm ocean water.
The water’s temperature must be at least 26°C.
Warm air rises from the warming ocean. The air carries water vapor,
the gas form of water. The water vapor cools as it rises. It turns back into
a liquid. This condensation forms clouds, releasing heat energy into the air
at the same time.
The large, dark clouds high above ground are photographed by a passenger
on an airplane entering the center of Hurricane Eloise.
As evaporation and
condensation continue, the air pressure at the surface of the ocean goes down.
That lets more water vapor into the air. That vapor rises higher, where it
condenses and releases still more energy.
The cloud columns grow higher and larger. In this way, a hurricane is a storm
that feeds itself. The more it grows, the more energy it releases. The more
energy it releases, the more it grows.
How Much Energy?
The illustrations above show different details of a hurricane including
rain bands, eye wall and temperature.
Diagrams courtesy of University Corporation for Atmospheric Research
In a day, a hurricane can release an amount of energy equal to all of the
electricity the entire world can generate in 200 days! And the thing is, many
hurricanes don’t just last a day. They keep building as long as they
keep getting energy from warm water. But if a hurricane moves over land or
colder water (with temperatures below 26°C it
loses its energy source. It starts to fizzle out.
The Rating System: How Do Hurricanes Rate?
Scientists use different systems to rate
the intensity of hurricanes and other severe storms. The Beaufort
scale classifies storms based on the speed of their winds. Category 1 weather
is marked by no wind at all. Category 12 storms have wind speeds over 119
kph. That’s the lowest level of a hurricane.
scale was designed to measure hurricanes. It picks up where the Beaufort
scale leaves off. Category 1 hurricanes on the Saffir-Simpson scale correspond
to low-end Category 12 storms on the Beaufort scale. The Saffir-Simpson scale
goes up to Category 5 - wind speeds more than 250
kph. Hurricane Katrina, the storm that devastated New Orleans in 2005,
was a Category 5 hurricane.
Movement and Direction
Hurricanes and cyclones may spin different directions but they're both powerful
storms that have both positive and negative effects.
Hurricanes are constantly moving. Air currents
in the atmosphere—as high as 15,250
meters - push them along. These air currents are called steering winds
because they seem to steer hurricanes.
As the winds move, they spin. This is due to something called the Coriolis
effect. In the Northern Hemisphere, hurricanes spin counterclockwise.
In the Southern Hemisphere, hurricanes spin clockwise.
Hurricane Damage at Sea and on Shore
Hurricane Wilma's strong winds and heavy rains forced people to wade through
the flooded streets of Havana.
Hurricanes that stay out at sea can cause
such high waves, powerful winds, and heavy rain that even huge cargo ships
can be blown off course or wrecked. But a hurricane that reaches land can be
a real killer.
Because a hurricane can be hundreds of kilometers across, people in the area
begin to feel the effects hours before it reaches land. The winds arrive
first, bringing lots of rain. Strong winds blow roofs off buildings and knock
down trees and power lines. The storm surge—a rise in sea level caused
by hurricanes—is responsible for most hurricane-related deaths. The storm
surge can cause sudden flooding and can even harm habitats where fish breed.
Mangrove forests have been destroyed for shrimp farms, leading to less protection
from hurricane impact.
Some natural barriers such as mangroves help
to buffer the shore from the impact of high winds, large waves, and erosion. Conservation
of mangrove areas has become an important part of coastal ecology and minimizes
the negative impact of hurricanes.
Hurricane Katrina left the people of New Orleans in the USA homeless. Many
people stayed in temporary shelters at stadiums and school gyms.
Flooding and mudslides are also problems farther inland because hurricane
rains spread over such a wide area. The rotating winds of a hurricane can spin
off into tornadoes. Flooding and heavy rains can destroy water treatment facilities,
which can lead to pollution and disease.
Flooding can leave behind standing water, which can cause a bump in the mosquito
population. And crowded shelters—filled with people who have lost their
homes—make it easier for diseases to spread.
Are Hurricanes Good for Anything?
Believe it or not, hurricanes do bring some
benefits. The most obvious one is that they bring rain. Too much can be catastrophic,
but some regions depend on hurricanes for their rainfall. Half of Japan’s
rainfall is the result of typhoons. In 1969, Hurricane Camille helped end the
threat of a drought in parts of Tennessee and Kentucky in the USA.
Hurricane Camille's powerful winds uprooted an entire tree that fell on
Also, a hurricane churns up the water so much that surface water temperatures
are lowered. Sometimes they’re lowered enough to make conditions less
favorable for other hurricanes in the same area. Last, if it weren’t
for hurricanes, the tropics would be too hot. Hurricanes suck up the heat and
shift it away from the equator.
Studying and Forecasting Hurricanes
Scientists use a wide range of tools to study
hurricanes. Weather satellites can
track storms from space. Radar can follow storms as they move across a state.
(Some TV weather reporters use radar to watch storms move through a city!)
Organizations like the National Oceanic and Atmospheric Administration (NOAA)
also use airplanes to study hurricanes and other weather. Planes fly into hurricanes
and release tubes called dropsondes into
the eyes of hurricanes. Parachutes are attached to the dropsondes. Right before
they splash down, they transmit important scientific readings to the airplane.
These readings can tell scientists whether the hurricane is getting weaker
An airplane flies into a hurricane to monitor its conditions using special
What Do Scientists Learn?
Weather scientists, called meteorologists,
study hurricanes so we can all be better prepared when they happen. By knowing
how hurricanes form, how they travel, and what happens when they reach populated
areas, we can stay safer and minimize the damage they cause.
Technology helps us better forecast the behavior of storms. Japan on September
20, 1996: The blue in the image represents low wind speeds and red the highest
wind speeds on the ocean surface.
Alvin, Bertha, Christobal . . .
Different parts of the world use different lists of names for hurricanes and
major storms. Usually the same names are rotated every four or six years. The
first storm of the season is given the first name on that year’s list.
The second storm of the season gets the second name, and so on. For really
destructive storms, the World Meteorological Organization sometimes takes names
off the list. Once is enough.