community-based disaster risk management and the media media kit

Community-based TYPHOON
Preparedness
chapter 3. useful information for the media
A TYPHOON is an intense tropical disturbance characterized by a low
pressure area at the center. In the Northern Hemisphere, as a result
of the earth’s rotation about its side, the wind blows counterclockwise
around the center of a low pressure area, and in the Southern
Hemisphere, the wind blows clockwise. The typhoon is the strongest of
a class of weather disturbances called tropical cyclones.
Formation of Typhoon
• Warm, moist air above the sea rises quickly to the cooler high
altitudes causing a very low pressure area and formation of cumulus
nimbus clouds.
• Surrounding air at the sea surface moves in to take the place of the
rising air. Rotational forces of the earth result in a circular motion
of the winds and cloud formations around the central low-pressure
area. The motion is clockwise in the South Pacifi c.
• Colder air is drawn slowly to the center of the system forming the
eye of the storm.
• Winds close to the eye become very strong (hurricane force).
• Entire cyclone systems are moved along by the trade winds at
speeds of between 10-25 km per hour.
The Eye of the Typhoon
The “eye” of a typhoon is a small central area of some 10 to 50 kilometers
in diameter. It is characterized by relatively calm or light winds, clear to
partly cloudy skies, high humidity, warm temperatures, and usually fi ne
weather.
Classifi cations of Tropical Cyclones
Tropical cyclones are classifi ed according to the strength of the
accompanying winds. The three categories into which tropical cyclones
fall are:
• Tropical Depression. Maximum wind speed near the center is less
than 63 kilometers per hour
• Tropical Storm. Maximum wind speed near the center ranges from
63 to 118 kilometers per hour
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