1. HYDROMETEOROLOGICAL
HAZARDS
BY: Shemayca Culata

2. HYDROMETEOROLOGICAL HAZARDS
Processes which involve the interaction of the
atmosphere, bodies of water, and land which
pose threat to lives and human property.

3. AT THE END OF THIS CHAPTER, STUDENTS SHOULD BE ABLE TO:

4. TYPHOONS

5. TYPHOONS
It is a severe weather disturbance characterized by
strong winds and heavy rains which revolve around
central low pressure area. It is the most powerful
type of tropical cyclone that forms in the
northwestern Pacific Ocean. The word “typhoon”
is derived from the Chinese term “Tai Fung” which
can be broken down into “ta” , which means big
and “fung”, which means wind.

6. MAJOR TYPES OF TROPICAL CYCLONES
1. TROPICAL DEPRESSION- wind speed up to 62kph
2. TROPICAL STORM- wind speed ranging from 63-
118kph
3. TYPHOON- wind speed greater than 118kph ( it is
called hurricane in northeast Pacific and northern
Atlantic regions)
4. SUPER TYPHOON- wind speed exceeding 220kph.

7. SEASONAL VARIABILITY OF TROPICAL CYCLONE ACTIVITY
Tropical cyclone activity :
 Lowest in May and increases gradually through June.
 Increases from July until September
 Level activity during August
 November, the activity level dies off
 TYPHOON HAIYAN(YOLANDA) IS THE POSSIBLY STRONGEST TYPHOON IN
PHILIPPINE HISTORY. DEATH TOLLS ALLEGEDLY REACHED MORE THAN
6OOO ACCORDING TO NDRRMC.

8. TROPICAL CYCLONE STRUCTURE
A tropical cyclone, on the average, has a
total diameter of 550 km but can have a
diameter more than 2000 km wide. Its basic
structure is composed of an eye, an eye wall,
and surrounding rain bands.

9. EYE
It is the lowest atmospheric pressure in the
structure of a tropical cyclone.
In the eye, with diameter which may span 20-65
km wide, winds are weak, the temperature is
warm, and the sky is clear- everything is calm and
it is as if no weather disturbance is going on in a
region over which the eye passes.

10. EYE WALL
The region immediately surrounding the
tropical cyclone’s center and which can reach
as high as 15km above mean sea level, brings
the strongest winds, heavy rains, and
turbulence shortly after the passage of the
eye.

11. RAIN BANDS
These are the spiralling strips of clouds in the fringes of
tropical cyclones which are associated with rainfall. The
tropical cyclone blow counterclockwise in the Northern
Hemisphere and clockwise in the Southern Hemisphere
due to Coriolis effect. The Coriolis effect describes the
deflection of an object’s motion due to the earth’s
rotation about its axis. In Northern Hemisphere, the air
deflects to the right. In Southern Hemisphere, the
deflection is to the left.

12. BASIC PARTS OF A TROPICAL CYCLONE

13. WHY DO TROPICAL CYCLONES FORM?
Tropical cyclones form as a result of the
atmosphere’s natural tendency to maintain
equilibrium by redistributing heat through
wind from the equatorical regions to the polar
regions. This mechanism prevents the tropical
areas from getting excessively hot and the
polar regions from becoming extremely cold.

14. IMPORTANCE OF TROPICAL CYCLONE
If not for tropical cyclones, there would be severe
environmental imbalances.
Rainfall brought by tropical cyclones replenishes ground
water and surficial water.
Flora and fauna in the Philippines are heavily reliant on
tropical cyclones for source of water.
50% of average annual rainfall in the country is derived
from typhoon-related rainfall.

15. HOW DO TROPICAL CYCLONES FORM?
 Tropical cyclones form both in northern and southern hemisphere at
latitudes 5 to 30 degrees away from the equator(trade wind belt) in parts of
the open ocean where water temperatures reach at least 26 degrees
Celsius to depth more than 60 meters.
 Air masses increasingly heats up and rise.
 Mainly due to Coriolis effect.
 Drier air from higher altitudes is sucked into the center of tropical cyclone
preventing the formation of clouds and, therefore rainfall. This explains
why the “eye” of the tropical cyclone is calm.

16. EFFECTS OF TROPICAL CYCLONE
 STRONG WINDS- which cover a much larger area during tropical
cyclones, cause the most obvious damage.
 STORM SURGE- localized unusual increase of sea water level
way above the predicted asrtronomical tide level, happens
primarily due to intense winds and lowered atmospheric
pressure that accompany intense tropical cyclones passing from
the sea to land.
 HEAVY RAINS- unlike strong winds and storm surges, actually
occur in tropical cyclones of lower intensity. Flooding due to
heavy rains is usually worse during tropical depressions and
tropical storms.

17. MEASURES FOR MITIGATING THE DESTRUCTIVE EFFECTS OF TYPHOONS
1. Determining areas prone to typhoon-
related disaters
2. Implementing legislation involving
land use planning, zoning, and
building standards.
3. Weather forecasting and monitoring

18. CENTRE OF JAPAN METEOROLOGICAL
AGENCY
Is one of the six worldwide Tropical Cyclone
RSMCs in charge of issuing official warnings
for the entire Western Pacific Ocean and
South China Sea Region.
RSMC Tokyo-Typhoon Center of the Japan
Meteorological Agency is also responsible for
naming typhoons.

19. NAMES OF TROPICAL CYCLONES

20. REVISED LIST OF NAMES FOR TROPICAL CYCLONES WITHIN
THE PHILIPPINE AREA OF RESPONSIBILITY

21. 4. EFFECTIVE PUBLIC TYPHOON WARNING
SYSTEMS
To help citizens prepare for the onslaught of the
storms, PAGASA issues Public Storm Warning
Signals that indicate the intensity, the areas that
will be affected and the forecast direction and
speed of the tropical storm or typhoon.

22. THE PUBLIC STORM WARNING SYSTEM
(PSWS) IS AS FOLLOWS:
 PSWS No. 1: The first signal indicates that the area affected should expect intermittent
rains within at least 36 hours. Winds of 30 kph to 60 kph should be expected, although it is
unlikely that they will cause significant damage. As a precaution, classes in all public and
private pre-schools are automatically suspended.
 PSWS No. 2: The second warning signal is raised in areas that will experience winds of 60
kph to 100 kph within at least 24 hours. Light to moderate damage is expected. Some
trees may be uprooted and roofs blown away. People traveling by air and sea are
cautioned, and disaster preparedness agencies should be alerting their respective
communities. Classes from pre-school to high school are suspended.
 PSWS No. 3: When the third warning signal is raised, people are advised to seek shelter
inside strong buildings, evacuate low-lying areas, and stay away from coasts and
riverbanks as moderate to heavy damage is expected. Winds of 100 kph to 185 kph are
expected within at least 18 hours. The winds could topple trees and destroy crops and
houses made of light materials. Widespread disruption of electrical power and
communication services is also expected. Classes at all levels are automatically suspended.

23. THE PUBLIC STORM WARNING SYSTEM
(PSWS) IS AS FOLLOWS:
 PSWS No. 4: The fourth storm warning signal indicates that a very intense typhoon with
winds of more than 185 kph may be expected within at least 12 hours. The typhoon is
potentially very destructive. Large trees are expected to be uprooted and residential and
institutional buildings could be severely damaged. Travels and outdoor activities should be
cancelled.
 PSWS No. 5: This recently added storm warning signal is raised when a super typhoon will
affect an area. Very powerful winds of more than 220 kph may be expected in at least 12
hours. This typhoon is "extremely destructive or catastrophic" to the community as almost
total damage to structures is expected. Most residential and institutional buildings may be
severely damaged, and only a few crops and trees will be left standing. Evacuation to safer
shelters should be completed early as it may already be too late if it hasn't begun. The
disaster coordinating councils concerned and other disaster response organizations should
be fully responding to emergencies by this time or completely ready to immediately
respond to the calamity.

24. THANK YOU!!
Your patience is appreciated.