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Hurricanes

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Grade 12 Climatology. SA curriculum. Hurricanes.

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Hurricanes

  1. 1. What are the causes and effects of hurricanes? Hurricanes Click here for a playlist on hurricanes By the end of this section, you will: Know how hurricanes are formed. How Hurricanes are named. Weather patterns of Hurricanes. Factors necessary for their development. The stages of development. Long and short term effects. Characteristics of a Hurricane. Case study Hurricane Katrina. Scoop It
  2. 2. FAMILY OF TROPICAL CYCLONES INFRARED SATELLITE PHOTOGRAPH
  3. 3. Hurricanes What is a hurricane? A violent cyclonic storm that develops in the tropical region with wind speeds are > 74 mph lasting for several days. In which direction does a hurricane rotate? Counterclockwise (NH) Clockwise (SH) Is the pressure inside the hurricane high or low? Low
  4. 4. How are hurricanes classified?
  5. 5. How do hurricanes form? Source: http://www.boardworks.co.uk/
  6. 6. Hurricane formation Source: http://www.boardworks.co.uk/
  7. 7. Naming of Hurricanes
  8. 8. Tropical Cyclone Structure • Doppler radar showing hurricane main parts: – Eye – Eyewall – Rainbands. • Counter-clockwise rotation. (NH) • In very center of the storm, air sinks, forming an "eye" that is mostly cloud-free.
  9. 9. Necessary factors for the formation of Hurricanes Complete the following details! Go into editing mode to do so. Factor or Condition Sea temperature of at least 27 Influence on formation process C Heat is needed for convection High Humidity Latent heat is released during condensation Unstable Air Unstable air to cause rising / convection of air Little Surface Friction Friction slows down the movement of the Tropical Cyclone Light Variable Winds Strong winds inhibit the development of the vortex Low air pressure Rising air associated with a LP is required for cloud formation Divergence of air in upper levels Stimulates circulation and the formation of votices
  10. 10. TROPICAL CYCLONE: DEVELOPMENT Formative Stage pressure ABOVE 1000 hPa MATURE Stage pressure WELL BELOW 1 000hPa source: http://sageography.myschoolstuff.co.za Developing Stage Pressure BELOW 1 000 hPa Degenration/ Dissipation Stage pressure RISES
  11. 11. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS FORMATIVE STAGE Complete the following details! Go into editing mode to do so. AIR PRESSURE TEMPERATURE CLOUD COVER, RAIN LP develops over the sea. Pressure is above 1000 hPa’s. Convergence of air. Vortex forms High temperatures and humidity that release latent heat and strengthen the LP. Cirrus and Cumulus clouds. Light rain. WIND Winds in active quadrant reach speeds of gale force winds. AREA INFLUENCED Small area is influenced,20 km from the “eye”.
  12. 12. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS DEVELOPING STAGE Complete the following details! Go into editing mode to do so. AIR PRESSURE TEMPERATURE CLOUD COVER, RAIN WIND AREA INFLUENCED
  13. 13. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS MATURE STAGE Complete the following details! Go into editing mode to do so. AIR PRESSURE TEMPERATURE CLOUD COVER, RAIN WIND AREA INFLUENCED
  14. 14. TROPICAL CYCLONE: ASSOCIATED WEATHER CONDITIONS DEGENERATION STAGE / DISSIPATING STAGE Complete the following details! Go into editing mode to do so. AIR PRESSURE TEMPERATURE CLOUD COVER, RAIN WIND AREA INFLUENCED
  15. 15. Stages of Development How do you know a Hurricane is in the dissipating stage? (Go into editing mode and complete the following: 1) 2) 3)
  16. 16. Most dangerous part of the Hurricane
  17. 17. Eye of a Hurricane
  18. 18. “Eye” of a Hurricane.
  19. 19. Development of Tropical Cyclones 3) As air rises, moisture condenses out, warming air and allowing it to continue rising 1) Warm, moist air spirals towards center of Hurricane 5) As pressures decrease, winds intensify and even more warm moist air is forced to converge and rise 2) Convergence of air forces air to rise L 4) As air rises, it causes even lower pressures at the surface
  20. 20. In the short-term Short-term effects will normally only last a few days or weeks. They will not cause any lasting or permanent damage. Examples may include: slight damage to land and/or buildings temporary migration of the population a disruption to power supplies. Can you think of any other short-term effects that might arise?
  21. 21. The long run Long-term effects can include large-scale destruction of property, or a complete alteration of the physical landscape. These pictures show the Chandeleur islands in the USA before and after Hurricane Katrina. As you can see, their geography has been permanently altered by the hurricane. Can you think of any other long-term effects that might arise?
  22. 22. Long and short term effects of Hurricanes Fill in the Short and Long-term effect!
  23. 23. Characteristics of a Tropical Cyclone Equator/Ewenaar From EAST to WEST EYE No wind, rain & Clouds DESTRUCTION •Storm winds •Torrential rain •Flooding Turns EAST at 30° source: http://sageography.myschoolstuff.co.za DISSIPATES •No Moisture •No warm air •Friction
  24. 24. Characteristics of a Tropical Cyclone NAME Alphabet Andrew Bonny Carl Debora MOVEMENT ORIGIN From E to W In tropics Away from OCEANS Equator Not nearer Turns east than 5°N/S from at 30° equator IN EYE No : Wind Clouds Rain DISSIPATION Over land No Moisture No Warm air Friction WEATHER Before eye During eye After eye source: http://sageography.myschoolstuff.co.za DESTRUCTION Storm winds Very hard rain Flooding MANAGED Sand bags Early warning Track storm Services Inform people Evacuation
  25. 25. Characteristics of a Hurricane! Complete the following details! Go into editing mode to do so. Originate (Latitude): Movement (direction): Rotation: Wind belt: Diameter: Weather: Named: Caused by:
  26. 26. TROPICALCYCLONE - MANAGEMENT source: http://sageography.myschoolstuff.co.za
  27. 27. Preparing for the worst! What precautions should be taken when there is a Hurricane warning! Avoid crossing strongly-flowing rivers at causeways /drifts. Dwellings very close to rivers / floodplains should be evacuated. Farmers should move pumps away from rivers. Small / medium sized fishing boats should return to port. Small fishing boats should be moved well above the high water mark. Listen to the radio / television for weather reports. Listen to the advice of the local disaster risk management officials.
  28. 28. Hurricane Katrina Hurricane Katrina was the most powerful hurricane to hit the USA in known history. It hit New Orleans on the morning of the 29th August 2005 bringing with it terrible destruction. New Orleans Winds of over 250 kilometres per hour were recorded as Katrina hit the coast, causing a storm surge 8.5 metres high.
  29. 29. Devastation At first New Orleans seemed to have weathered the worst of the hurricane, but later storm surges breached the city’s protective levees. People that had not left their properties were stranded and had to wait to be rescued or wade through polluted floodwater. It was a hugely devastating natural disaster.
  30. 30. The aftermath How badly did Hurricane Katrina affect New Orleans? Flood levels were over six metres high. 80% of the city was flooded. Over a million homes were left without electricity. There were 700 deaths in New Orleans. Over a million people had to leave their homes. Damaged oil refineries spilt 24 million litres of crude oil. Over $81 billion worth of damage was done. Click here for a PowerPoint on Hurricane Katrina
  31. 31. In the news Source: http://www.boardworks.co.uk/
  32. 32. You are the mayor Source: http://www.boardworks.co.uk/
  33. 33. EXAMINATION QUESTION Tropical easterlies •Coriolis force •Warm water •Moisture •Land •No warm water •Friction 1 Give ONE similarity between Hurricanes and Tropical cyclones on the map. 2 3 4 5 Explain the point of origin of both hurricanes and tropical cyclones on the map. Why do these tropical cyclones move from east to west? Why do tropical cyclones weaken as they move over Madagascar. Why is the impact of tropical cyclones more severe in developing countries? source: http://sageography.myschoolstuff.co.za

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