THE TROPICAL CYCLONE
Cyclone- is a big whirling mass of
strong winds and rain moving in counter
clockwise direction in the northern
All tropical cyclones originate on the
western sides of the oceans in the
doldrums, the cyclones move westward
and away from the equator.
Around the world, tropical cyclones
are called by different names. They come at
different times of the year in different
places. For example, in our country the
tropical cyclones are called “bagyo”. They
usually occur from September to November.
By international agreement, tropical
cyclones are classified according to speed of
the wind. The weakest is called a tropical
depression with a maximum wind speed of
up to 63 kilometers per hour (kph) or
approximately less than 25 mile per hour
A depression exist when there is low
pressure over a large enough area to be
plotted on the weather map. The low
pressure near the ocean surface draws in
warm, moist air which feeds more
The winds swirl slowly around the lopressure area at first. As the pressure
becomes even lower, more warm, moist
air is drawn in, and the winds blow faster.
A tropical storm has developed when
the maximum wind speed is 64 to 118 kph
(25 to 75 mph) and with closed isobars.
Near the center of a tropical storm is
a column of warm air, The warmer the
column is, the lower the pressure at the
surface falls. The low pressure, in turn
draws more air into the storm. As more
air is pulled into the storm, the winds
Typhoon- is an intense tropical
cyclone with maximum wind speed
exceeding 118 kph.
Typhoon or hurricane has a welldeveloped eye at its center, surface
pressure drops to its lowest in the
In the eyewall of the hurricane is its
strongest winds. The warm air spirals
upward. The speed of the winds in the
eyewall is related to the diameter of the
eye. A hurricane’s winds blow faster if its
eye is small. If the eye widens, the winds
Very heavy rains fall from the eyewall
and bands of the hurricane. The dense
clouds that swirl around the eyewall are
called rainbands. They can produce more
than 5cm of rain per hour that can
cause floods, and flash floods.
Image of typhoon Ondoy that brings a
lot of damage and loss lives to people in
The center of a typhoon is called the eye.
It is the center of calm. It is normally 40
km in diameter. In the eye of the storm,
warm air is rising and there are no
clouds. At the edge of the eye, the speed
of the wind is fastest. The eye is
characterized by calm air and sunny sky.
The distribution of rain is also not
uniform. There is no rain in the typhoon’s
In fact, we can see the sun shining if the
eye is over us.
There is much heavy rain in the
middle, between the eye and the edge.
There is less rain at the edge.
The eyewall is the rim of the eye. It
has the stongest winds with very heavy
rain, and a very dark sky. The rainbands
are bands of heavy clouds which supply
water for the abundant rain lasting for