SCIENCE 8

Quarter 2 - Week 4
Name of Learner: ____________________________ Score: __________________________
Section: _____________________________________ Date: ___________________________
LEARNING ACTIVITY SHEET
Understanding Typhoons

Background Information for Learners

Our country is located near the equator surrounded by the bodies of water which favor the formation of a tropical cyclone it is
one of the most destructive disasters known to man.
It is one of the Earth's strongest forces, a combination of strong, howling winds and heavy precipitation. Typhoons that enter the
Philippine Area of Responsibility become more frequent and violent, causing great damage and loss to many lives and properties.
But how does this force of nature form? How do typhoons develop? What are some factors that affect a typhoon? These are some of
the important questions that you will seek to answer in this module.

Learning Competency:
1. Explain how tropical cyclones form;
2. Explain how typhoons develop;
3. Describe the factors that affect a typhoon

What Kind of Air Causes the Formation of Typhoon?

In the warm, open seas just off the equator, the water is considerably warmer; so is the air. The
warm air helps the also-warm water evaporate faster; and this hot, moist mass of air would go up,
following the basic tenet that "warm air goes up, cool air goes down." (Figure 5)
Up in the air, the water vapor cools down and condenses, and the heat is released back Figure 5: Movement of Warm Air
to the air; this heat makes the air lighter, making it move further up. It then triggers air from https://www.weather.gov/jetstream/tc
outside the system to go inward, then upward, towards the system. This air flow helps more water to
evaporate, joining the clouds and precipitation already massing up in the air.( Figure 6)

If the process continues, energy and precipitation accumulate further, and the winds speed up.
Once the winds reach a certain speed, it then becomes a tropical cyclone.
The movement of the Earth also affects this process: the wind, instead of moving in straight lines,
moves in a spiral pattern due to the so-called Coriolis Effect. This causes the easily-identifiable,
spiraling cloud systems we see in satellite photos.( Figure 7)
Figure 6: Wind moves in a spiral pattern
2019/

The word tropical cyclone is composed of two distinct words that completely describe its
characteristic. The term “tropical” refers to its geographical starting point, which is usually hot and
humid; whereas “cyclone” is a meteorological term which refers to its cyclonic circulation where the
strong winds in the Northern Hemisphere circulate counter –clockwise and clockwise in Southern
Hemisphere.
How a tropical cyclone is called differs based on where it formed. In the northwest Pacific it is
called a typhoon; in the southwest Pacific and in the Indian Ocean, it is a cyclone; and in the eastern
Pacific and in the Atlantic, it is a hurricane. Figure 7: Spiralling cloud system
Though a tropical cyclone is known in different names, it has
a uniform procedure of how it is formed or developed. Among other tropical cyclones, we often heard the word typhoon and hurricane
in the weather reports. Here, in the Philippines, we use typhoon or “ bagyo”.

Most tropical cyclones occur in the area where the Northeasterly and Southeasterly trade winds converge. This area is called
ITCZ or Intertropical Convergence Zone, circulating near the equator, and it is known for its lowest surface pressure, where the
converging air ascends ( causing “ low-pressure” on Earth’s surface), condenses and strengthens into sufficiently strong tropical
disturbances.

T he lowest pressure is at the eye of a tropical cyclone. In fact, all tropical cyclones have low air pressure at the center.
Different parts of a tropical cyclone are:
• Eye –is the area of lowest atmospheric pressure, with diameter which may span 20-65 km wide, winds
are weak, the temperature is warm, and the sky is clear-everything is calm.
• Eye wall –the region immediately surrounding the eye, brings the strongest winds, heavy rains and turbulence
Note: Practice Personal Hygiene Protocols at all times..
 • Rain bands - spiraling strips of clouds associated with rainfall.
Table 1: Tropical Cyclone Categories

Factors affecting Typhoon

A Category Maximum Wind Speed kilometer per hour (kph) typhoon can
become stronger
Tropical Depression 64
and be upgraded into
Tropical Storm 118
a super typhoon as
Typhoon 200
long as the conditions
continue to become favorable for the cyclone. However, despite of its destructive power, a typhoon can cease to intensify its tropical
characteristics due to several factors
1. Cold waters
The absence of moisture from warm ocean waters means the absence of a typhoon’s “fuel” source once it lacks its access to this kind
of environment. typhoons depend on warm water to maintain themselves but when the storm moves over cold water, it loses its energy
source, which is the evaporating water from ocean surface. it weakens due to the deprivation of warm water by moving over bodies of
water with a temperature below 26.5 OC.
2. No Water
A typhoon will drastically deteriorate once its eye moves over land. The air over land cools quickly due to specific heat causing the
typhoon to quickly lose intensity.
3. Wind shear
Refers to the difference between the speed shear (wind speed) and its directional shear over relatively a short distance within the
atmosphere.

TEST YOURSELF
Directions: Read and answer the questions in the best way you can. Write the letter of your answer on the space provided before each
number.

_____1. What causes the formation of low-pressure area that can lead to the development of a typhoon?
A. cold and dry air
B. cold waters surrounded by warm conditions
C. warm waters surrounded by cold conditions
D. very low moisture or humidity
_____2. Which of the following best describes a typhoon?
A. A low-pressure area C. Heavy rains and flood
B. Hurricane D. Mature tropical cyclone
_____3. Which of the following is not a name for a tropical cyclone?
A. Hurricane C. Typhoon
B. Cyclone D. Depression
_____4. Identify the sea temperature required for the formation of a tropical cyclone.
A. 25.5°C B. 29.5°C C. 26.5°C D. 30.5°C
_____5. What is the category of tropical cyclone when it reaches the maximum sustained winds of 58 km/hr?
A. tropical storm B. typhoon
C. tropical depression D. super typhoon

References:
SCIENCE Grade 8
Support Material for Independent Learning Engagement (SMILE)
Quarter 2 – Module 4: Understanding Typhoons
First Edition, 2021

Note: Practice Personal Hygiene Protocols at all times..

 WEEK 4
TEST YOURSELF:
1. C
2. D
3. D
4. A
5. D

Note: Practice Personal Hygiene Protocols at all times..