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The slides teach us about tropical cyclones
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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.
Cyclones, Hurricanes, Typhoons Named according to
region where they develops
Cyclones – Develop over the Indian Ocean on worm waters
Hurricanes - Develop over Atlantic and eastern Pacific Oceans
Typhoons – Develop over western Pacific Oceans
All produce similar effects
Typhoon Odessa, Philippines
Eye
Fact.
The strongest of these cyclones storms are known in the US and other parts of the Atlantic ocean
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
Tropical Cyclones Introduction
Tropical cyclones are intense, rotating, low-pressure storms
Develop over warm, tropical oceans
Produce strong winds and heavy rainfall
Can lead to immense flooding
Destructive Winds
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.
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
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
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
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
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.
Coriolis Effect
Northern hemisphere winds are blowing counter-clockwise around center core
Southern hemisphere winds are blowing clockwise around center core
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
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
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
Tropical Cyclone Appearances
ITCZ
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
Storm Path
India
Bay of Bengal
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
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
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.
Ocean Surface
The ocean surface latent heat is later released when the air begins to rise and water vapor condenses into clouds and rain
References Ashley Proctor Samone Proctor Chelsea Addison
(3) 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
(8) 1970 Bhola cyclone. (2009, November 22). In Wikipedia, The Free Encyclopedia. Retrieved November 23, 2009, from http://en.wikipedia.org/wiki/1970_Bhola_cyclone
(1) Catto, N., Hyndman, D., Hyndman, D. (2009). Natural Hazards and Disasters. Toronto, ON: Nelson Education
(6) Earth Science Australia. (2009). Tropical Cyclones. Retrieved November 22, 2009, from http://earthsci.org/flood/J_Flood04/cyclone/cyclone.html
(4) National Weather Service. (2008, October 8). Tropical Weather. Retrieved November 22, 2009, from http://oceanservice.noaa.gov/education/yos/resource/JetStream/tropics/tc.htm
(5) Nelson, S.A. (2009, October 30). Exceptional Weather – Tropical Cyclones. Retrieved November 22, 2009, from http://www.tulane.edu/~sanelson/geol204/tropical_cyclones.htm
(2) Tropical cyclone. (2009, November 22). In Wikipedia, The Free Encyclopedia. Retrieved November 20, 2009, from http://en.wikipedia.org/wiki/Tropical_cyclone
(7) 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