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The Physical Characteristics of Tropical Cyclones

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The Physical Characteristics of Tropical Cyclones

  1. 1. The Physical Characteristics of Tropical Cyclones<br />Case Study: The 1970 Bhola Cyclone <br />
  2. 2. Cyclones, Hurricanes, Typhoons<br />Named according to region (1)<br />Cyclones – Develop over the Indian Ocean(1)<br />Hurricanes - Develop over Atlantic and eastern Pacific Oceans(1)<br />Typhoons – Develop over western Pacific Oceans(1)<br />All produce similar effects(1)<br />Eye<br />Typhoon Odessa, Philippines<br />
  3. 3. Developmental Stages<br />Progression: depression storm cyclone(2) <br />Classified according to wind speeds(2)<br />Tropical Depression - less than 39 m/h (2)<br />Tropical Storm - between 39 m/h and 73 m/h (2) <br />Tropical Cyclone - at least 74 m/h (2) <br />
  4. 4. Tropical Cyclones Introduction<br />Tropical cyclones are intense, rotating, low-pressure storms (2)<br />Develop over warm, tropical oceans(2) <br />Produce strong winds and heavy rainfall(2)<br />Can lead to immense flooding(2) <br />Destructive Winds<br />
  5. 5. Formation of Tropical Cyclones<br />Warm water generates formation of tropical cyclones(4)<br />Ocean temperatures must be at least 26.5°C(7)<br />Over warm oceans moist, humid air (water vapour)(4)<br />Warm air moves along the surface(4)<br />This air converges and rises rapidly(5) <br />Intense rising of air forms low pressure systems (7)<br />
  6. 6. Formation of Tropical Cyclones<br />As air rises, it cools, becomes saturated and condenses(4)<br />Water vapour condenses into liquid droplets(4)<br />Formation of thunderclouds(5) <br />Condensation releases heat stored in water vapour(4)<br />This latent heat warms the atmosphere(4)<br />Air becomes lighter causing strong updrafts(4)<br />
  7. 7. Formation of Tropical Cyclones<br />Air expands and diverges at higher levels(5) <br />Occurs only where wind speed/direction remain constant (no wind shear) (7)<br />Air moves in at surface taking the place of rising air(4)<br />This intensifies convergence(5)<br />Creates wind and increases rising movement(4)<br />Builds and progresses into a mature cyclone(5) <br />
  8. 8. Coriolis Effect<br />Spinning of earth on its axis produces wind deflections (Coriolis Effect) (7)<br />Causes rising air to spiral around center (core) (7)<br />Spirals with great force (7)<br />Winds are now rotating, rising and moving in to fill spaces (7)<br />Wind speeds increase and cyclone grows (7)<br />
  9. 9. Coriolis Effect<br />Northern hemisphere winds are blowing counter-clockwise around center core (6) <br />Southern hemisphere winds are blowing clockwise around center core (6) <br />
  10. 10. The Eye, Eyewall, Rainbands<br />The Eye - the clear, calm center of storm(4)<br />Cool air descends into this center (downdrafts)(4)<br />Eyewall – ring of thunderstorms close to eye(4)<br />Eyewall produces the most devastating winds(4)<br />Rainbands – curved groups of clouds andthunderstorms (4)<br />Rainbands travel away from eye in a spiral motion(4) <br />
  11. 11. Storm Surges<br />Occur when tropical cyclones reach land (3)<br />Storm surge – raised swell of water (3)<br />60 to 80 km across (3)<br />Around 2 to 5 meters higher than normal tides (3)<br />Created by heavy winds and cause flooding (3)<br />
  12. 12. Locations of Tropical Cyclones<br />Between 10 to 30° North and South of equator (2) <br />Within the tropic of Cancer and Capricorn (2)<br />Poleward side of the Intertropical Convergence Zone (2) <br />Zone of low pressure (ITCZ) (2) <br />Coriolis effect greatly reduced at equator (4)<br />No tropical cyclones occur at equator (4)<br />ITCZ<br />Tropical Cyclone Appearances<br />
  13. 13. Tropical Cyclone Categories<br />
  14. 14. Case Study: The 1970 Bhola Cyclone<br />Storm Survivors<br />
  15. 15. The 1970 Bhola Cyclone<br />November 12, 1970(8)<br />The deadliest tropical cyclone recorded(8)<br />Developed over Bay of Bengal(8)<br />Gathered speed as it moved northward(8)<br />Devastated East Pakistan (Bangladesh) and West Bengal of India(8)<br />India<br />Bay of Bengal<br />Storm Path<br />
  16. 16. The Bhola Cyclone Characteristics<br />Wind speeds reached 115 m/h (8)<br />Strength of a category 3 hurricane (8)<br />33 foot high storm surge (8)<br />Massive storm surge caused flooding and fatalities (8)<br />Bhola Cyclone on November 11, 1970<br />
  17. 17. The Bhola Cyclone - Damage<br />Storm surge: <br /><ul><li>Flooded low-lying islands
  18. 18. Wiped out crops
  19. 19. Destroyed whole villages
  20. 20. Demolished 85% of homes in the area (8)</li></ul>Estimated damage at 86.4 million dollars (8)<br />300,000 - 500,000 people were killed (8)<br />Great Bhola Cyclone<br />
  21. 21. References<br />(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<br />(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<br />(1)Catto, N., Hyndman, D., Hyndman, D. (2009). Natural Hazards and Disasters. Toronto, ON: Nelson Education<br />(6) Earth Science Australia. (2009). Tropical Cyclones. Retrieved November 22, 2009, from http://earthsci.org/flood/J_Flood04/cyclone/cyclone.html<br />(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<br />(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<br />(2) Tropical cyclone. (2009, November 22). In Wikipedia, The Free Encyclopedia. Retrieved November 20, 2009, from http://en.wikipedia.org/wiki/Tropical_cyclone<br />(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<br />

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