3. TROPICAL CYCLONE
• is a rotating, organized system of clouds and
thunderstorms that originates over the tropical waters.
Tropical cyclones rotate in a counterclockwise direction in
the northern hemisphere (conversely, clockwise in the
southern hemisphere). The term tropical cyclone
encompasses tropical depressions, tropical storms,
typhoons and hurricanes. ,
4. • After formation, tropical cyclones usually move to the
west and generally slightly poleward, then may "recurve,"
that is, move into the mid-latitude and back toward the
east. However, not all tropical cyclones recurve. It derives
its energy from the latent heat of condensation which
made them exist only over the oceans and die out rapidly
on land. The intensity of tropical cyclones vary, thus, we
can classify them based upon their degree of intensity.
5. THE CLASSIFICATION OF TROPICAL CYCLONES ACCORDING
TO THE STRENGTH OF THE ASSOCIATED WINDS AS ADOPTED
BY PAGASA (AS OF 01 MAY 2015) ARE AS FOLLOWS:
TROPICAL DEPRESSION (TD) - a tropical cyclone with maximum sustained winds of
up to 61 kph.
TROPICAL STORM (TS) - a tropical cyclone with maximum wind speed of 62 to 88
kph.
SEVERE TROPICAL STORM (STS) - a tropical cyclone with maximum wind speed of
89 to 117 kph.
TYPHOON (TY) - a tropical cyclone with maximum wind speed of 118 to 220 kph.
SUPER TYPHOON (STY), a tropical cyclone with maximum wind speed exceeding
220 kph.
6.
7. THE TROPICAL CYCLONE
• A tropical cyclone can be seen in a satellite image due to its
characteristic spiral/circular shape. The stronger and more intense
a tropical cyclone becomes, the more symmetrical the inner clouds
or rainbands are and a distinctive “eye” at the center of circulation
becomes visible. This means that a tropical cyclone tends to be
more circular and it’s center will have a cloudless region. Weather
forecasters use satellite images like that in Fig. 2 to track the
movement and estimate the intensity of tropical cyclones.
8.
9. THE WEATER RADAR
• Another way weather forecasters track the movement of
tropical cyclones is with the use of weather Radars.
RADAR is an acronym which stands for RAdio Detection
And Ranging. A Radar sends out electromagnetic waves
to the atmosphere that is then reflected by hydrometeors
(e.g. rain, clouds) present in the sky. An image is created
from the received signal and information on rain clouds
can be gathered. While radar images give more details of
a storm, it is limited to a range of approximately 400 km
from the radar site.
10.
11.
12. TOGETHER WITH THE FORECAST TRACK, PAGASA ALSO ISSUES THE PUBLIC STORM WARNING SYSTEM (PSWS) TO
WARN CITIZENS OF IMPENDING WIND STRENGTH. THE PSWS IS AS FOLLOWS:
Every year, an average of 19 tropical cyclones enter the Philippines Area of Responsibility (PAR), and about half (9-10) make landfall in the Philippines. In the Western Pacific Ocean, tropical cyclones can form in any month of the year.
MTSAT IR satellite image of Yolanda (Haiyan) on 7 Nov 2013
Fig. 3 shows the eye and parts of Yolanda (Haiyan) in the morning of 8 Nov 2013 when it made landfall in Eastern Visayas as observed by the Mactan (Cebu) Radar. The image is color coded depending on the amount of rain a cloud carries: Blue – light rain, green/yellow – moderate rain, red – intense rain.
Once a tropical cyclone enters PAR, a 5-day forecast track (previously 3-day) is issued by PAGASA every 6 hours at 5am, 11am, 5pm and 11pm. A forecast track gives the expected location of a tropical cyclone in the succeeding 24hour interval for the next 120 hours or 5 days.
Divide the class into groups of 5.
Distribute the school/school grounds maps to each of the groups.
Let learners analyze, based on the Teacher Tips, whether their school/school grounds is/are prone to typhoons and/or thunderstorms. Show a map of the Philippines for reference.
4. Bring the class outside to allow the learners to appreciate the location of their school relative to its surroundings with emphasis on topography, waterways/drainage system, mountain slopes, etc.
5. Ask each group to indicate areas in the map prone to hydrometeorological hazards discussed in class (floods, flash floods, storm surges):
6. Provide a color legend for the following hazards for standardization. Suggested color scheme:
7. Red – flood-prone, Orange – flash flood-prone, Purple – storm surge-prone
8. After finishing their hazard maps, ask each group to present their outputs.
1. Ask the groups to post their hazard maps in the classroom bulletin board
2. Ask the class to vote on the “best” hazard map, based on the evaluation grade, to be posted on the school bulletin board.
3. Encourage the learners to investigate the surroundings of the school, to appreciate their proximity to any of the waterways/water bodies that may contribute to the hazards of floods, flash floods, storm surges.
