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A tropical cyclone is a storm system characterized by a low-pressure center and numerous thunderstorms that produce strong winds and heavy
rain. Tropical cyclones strengthen when water evaporated from the
ocean is released as the saturated air rises, resulting incondensation of water vapor contained in the moist air. They are
fueled by a different heat mechanism than other cyclonic windstorms such as nor'easters, European windstorms, and polar lows.
The characteristic that separates tropical cyclones from other cyclonic systems
is that at any height in the atmosphere, the center of a tropical cyclone will
be warmer than its surroundings; a phenomenon called "warm core"
storm systems.
The term "tropical" refers
both to the geographical origin of these systems, which usually form in tropical regions of the globe, and to their
formation in maritime tropical air masses. The term "cyclone"
refers to such storms' cyclonic nature, with counterclockwise wind flow in the Northern Hemisphere and clockwise wind flow in the Southern Hemisphere. The opposite
direction of the wind flow is a result of the Coriolis force.
Depending on its location and strength, a tropical cyclone is referred to by
names such as hurricane, typhoon, tropical storm, cyclonic storm, tropical
depression, and simply cyclone.
While tropical cyclones can produce
extremely powerful winds and torrential rain, they are also able
to produce high waves, damaging storm surge,
and tornadoes. They develop
over large bodies of warm water, and lose their strength if they move over land
due to increased surface friction and loss of the warm ocean as an energy
source. This is why coastal regions can receive significant damage from a
tropical cyclone, while inland regions are relatively safe from receiving
strong winds. Heavy rains, however, can produce significant flooding inland,
and storm surges can produce extensive coastal flooding up to 40 kilometres (25 mi) from the coastline. Although their effects on human
populations can be devastating, tropical cyclones can relieve drought conditions. They also carry heat energy
away from the tropics and transport it toward temperate latitudes, which makes
them an important part of the global atmospheric circulation mechanism. As a result, tropical
cyclones help to maintain equilibrium in the Earth's troposphere,
and to maintain a relatively stable and warm temperature worldwide.
Many tropical cyclones develop when the atmospheric conditions around
a weak disturbance in the atmosphere are favorable. The background environment
is modulated by climatological cycles and patterns such as the Madden-Julian oscillation, El Niño-Southern
Oscillation, and the Atlantic multidecadal oscillation. Others
form when other types of
cyclones acquire tropical characteristics. Tropical systems are then moved
by steering winds in the troposphere;
if the conditions remain favorable, the tropical disturbance intensifies, and
can even develop an eye. On the other end of the spectrum, if the conditions
around the system deteriorate or the tropical cyclone makes landfall, the
system weakens and eventually dissipates. It is not possible to artificially
induce the dissipation of these systems with current technology.
A tropical cyclone is composed of a system of
thunderstorms that shows a cyclonic rotation around a central core or eye. A tropical cyclone is a generic term for a storm
with an organized system of thunderstorms that are not based on a frontal system.
Each individual tropical cyclone differs, but
several characteristics are common to most all tropical cyclones including a
central low-pressure zone and high wind speeds of at least 34 knots. At this point, the storms are given a
pre-determined storm name. Most
storms are accompanied by a lot of rain and storm surges near the shore. Often, once the storms make
landfall, the tropical cyclone can cause
tornadoes.
A tropical cyclone needs warm ocean temperatures in order to
form. Temperatures in the ocean need to be at least 82 degrees Fahrenheit in
order to form. Heat is drawn up from the oceans creating what is popularly
called a 'heat engine'. Tall convective towers of clouds are formed within the
storm as warm ocean water evaporates. As the air rises higher it cools and
condenses releasing latent heat which causes even more clouds to form and feed
the storm.
Rotation and Forward Speed
The rotation of tropical cyclones in the
Northern Hemisphere is counter-clockwise due to theCoriolis
Effect. The opposite is true in the
Southern Hemisphere.
The forward speed of a tropical cyclone can be
a factor in determining the amount of damage the storm will cause. If a storm
remains over one area for a long period of time, torrential rains, high winds,
and flooding can severely impact an area. The average forward speed of a
tropical cyclone is dependent
on the latitude where the storm is currently. Generally, at less than 30 degrees
of latitude, the storms will move at about 20 mph on average. The closer the
storm is located the the equator, the slower the movement. Some storms will
even stall out over an area for an extended period of time. After about 35
degrees North latitude, the storms start to pick up speed.
A good example of the fast formation of
tropical cyclones comes when several storms stack up in the ocean back-to-back.
Such an example occurred in 2009 with the formation of Ana,
Bill, and Claudette as seen in this satellite image. The storms were very close to
one another. Storms can also become entangle with one another in a process
known as the Fujiwhara Effect where tropical cyclones can interact with each
other.
Naming Tropical Cyclones
In the Atlantic Ocean and Eastern Pacific,
tropical cyclones are known as hurricanes. In the Western Pacific Ocean,
tropical cyclones are known as typhoons. In the Indian Ocean, a tropical
cyclone is called a cyclone. These names are described in the article – Is it a
typhoon, a cyclone, or a hurricane?
Specific storm names in each of the ocean
basins vary based on conventional naming practices. For instance, in the
Atlantic Ocean, storms are given names based on an alphabetical pre-determined
list of Atlantic hurricane names.
Severe hurricanes names are
