2. Tropical Cyclones
A tropical cyclone is a storm system
characterized by a large low-pressure
center and numerous thunderstorms
Tropical Cyclones: Grounds of rotating,
low-pressure storms that form around the
equator.
3. Cyclones, Hurricanes, Typhoons
Named according to region
where they develops
Cyclones – Develop over
the Indian Ocean on worm
waters
Eye
Hurricanes - Develop over
Atlantic and eastern Pacific
Oceans
Typhoons – Develop over
western Pacific Oceans
All produce similar effects
Typhoon Odessa, Philippines
4. Fact.
The strongest of these cyclones storms are
known in the US and other parts of the
Atlantic ocean
5. Developmental Stages
Progression: depression
storm
cyclone
Classified according to wind speeds
Tropical Depression - less than 39 m/h
Tropical Storm - between 39 m/h and 73 m/h
Tropical Cyclone - at least 74 m/h
6. Tropical Cyclones Introduction
Tropical cyclones are
intense, rotating, lowpressure storms
Develop over warm,
tropical oceans
Produce strong winds
and heavy rainfall
Can lead to immense
flooding
Destructive Winds
7. Formation of tropical cyclones
Tropical Cyclones require to basic
conditions to form: an abundant supply of
very warm ocean water and some sort of
disturbance to lift warm air and keep it
rising.
8. Formation of Tropical Cyclones
Warm water generates formation of tropical cyclones
Ocean temperatures must be at least 26.5°C which is worm
Over warm oceans
moist, humid air (water vapour)
Warm air moves along the surface
This air converges and rises rapidly
Intense rising of air forms low pressure systems
9. Formation of Tropical Cyclones
As air rises, it cools, becomes
saturated and condenses
Water vapour condenses into
liquid droplets
Formation of thunderclouds
Condensation releases heat
stored in water vapour
This latent heat warms the
atmosphere
Air becomes lighter causing
strong updrafts
10. Formation of Tropical Cyclones
Air expands and diverges at higher levels
Occurs only where wind speed/direction remain constant
(no wind shear)
Air moves in at surface taking the place of rising air
This intensifies convergence
Creates wind and increases rising movement
Builds and progresses into a mature cyclone
11. Coriolis Effect
Spinning of earth on its axis
produces wind deflections
(Coriolis Effect)
Causes rising air to spiral
around center (core)
Spirals with great force
Winds are now rotating,
rising and moving in to fill
spaces
Wind speeds increase and
cyclone grows
12. Conditions
These conditions exist in all tropical
oceans except the south Atlantic ocean
and the pacific, west of the South
American coast ocean waters in these
areas are somewhat cooler.
13. Coriolis Effect
Northern hemisphere winds are blowing counterclockwise around center core
Southern hemisphere winds are blowing clockwise
around center core
14. The Eye, Eyewall, Rainbands
The Eye - the clear, calm center of storm
Cool air descends into this center (downdrafts)
Eyewall – ring of thunderstorms close to eye
Eyewall produces the most devastating winds
Rainbands – curved groups of clouds and thunderstorms
Rainbands travel away from eye in a spiral motion
15. Storm Surges
Occur when tropical cyclones reach land
Storm surge – raised swell of water
60 to 80 km across
Around 2 to 5 meters higher than normal tides
Created by heavy winds and cause flooding
16. Locations of Tropical Cyclones
Between 10 to 30° North and South of equator
Within the tropic of Cancer and Capricorn Poleward side of
the Intertropical Convergence Zone
Zone of low pressure (ITCZ)
Coriolis effect greatly reduced at equator No tropical
cyclones occur at equator
ITCZ
Tropical Cyclone
Appearances
19. The 1970 Bhola Cyclone
November 12, 1970 The
deadliest tropical
cyclone recorded
Developed over Bay of
Bengal Gathered speed
as it moved northward
Devastated East Pakistan
(Bangladesh) and West
Bengal of India
India
Bay of Bengal
Storm Path
20. The Bhola Cyclone Characteristics
Wind speeds reached
115 m/h Strength of a
category 3 hurricane 33
foot high storm surge
Massive storm surge
caused flooding and
fatalities
Bhola Cyclone on November 11, 1970
21. The Bhola Cyclone - Damage
Storm surge:
• Flooded low-lying islands
• Wiped out crops
• Destroyed whole villages
• Demolished 85% of
homes in the area
Estimated damage at 86.4
million dollars 300,000 500,000 people were
killed
Great Bhola Cyclone
22. Mid-latitude Storms
Unlike mid latitude storms that derive
their energy from the contrast between
warm and cold air masses. Tropical
Cyclones oceans as water evaporates from
the ocean surface.
23. Ocean Surface
The ocean surface latent heat is later
released when the air begins to rise and
water vapor condenses into clouds and
rain
24.
Ashley Proctor Samone Proctor Chelsea Addison
(3)
(8)
(1)
(6)
(4)
(5)
(2)
(7)
References
Australian Government Bureau of Meteorology. (2009). About Tropical Cyclones. Retrieved November 22, 2009, from
http://www.bom.gov.au/weather/cyclone/about/about-tropical-cyclones.shtml
1970 Bhola cyclone. (2009, November 22). In Wikipedia, The Free Encyclopedia. Retrieved November 23, 2009, from
http://en.wikipedia.org/wiki/1970_Bhola_cyclone
Catto, N., Hyndman, D., Hyndman, D. (2009). Natural Hazards and Disasters. Toronto, ON:
Nelson Education
Earth Science Australia. (2009). Tropical Cyclones. Retrieved November 22, 2009, from
http://earthsci.org/flood/J_Flood04/cyclone/cyclone.html
National Weather Service. (2008, October 8). Tropical Weather. Retrieved November 22, 2009, from
http://oceanservice.noaa.gov/education/yos/resource/JetStream/tropics/tc.htm
Nelson, S.A. (2009, October 30). Exceptional Weather – Tropical Cyclones. Retrieved November 22, 2009, from
http://www.tulane.edu/~sanelson/geol204/tropical_cyclones.htm
Tropical cyclone. (2009, November 22). In Wikipedia, The Free Encyclopedia. Retrieved November 20, 2009, from
http://en.wikipedia.org/wiki/Tropical_cyclone
WikiAnswers. (2009). How do cyclones form? Retrieved November 23, 2009, from
http://wiki.answers.com/Q/How_do_cyclones_form&alreadyAsked=1&rtitle=What_causes_cyclones