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Class 1 powerpoint

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  • Sample answers:--Hazards: volcanic ejecta (pyroclastic material, ash); poisonous gases--Ways to Minimize Risk: avoid death/injury by not jumping into the volcano, or not jumping at all; in advance, plan a different route to avoid ash clogging engine
  • High windsWaves, floodingLow pressure weather systemsDangerous, sometimes lead to evacuationsImage: Hurricane Rita as a Category 5 hurricane. Source:
  • Image: Hurricane Rita as a Category 5 hurricane. Source:
  •… Daily contoured image of SST:
  • Public domain image.Associated text from It has been recognized since at least the 1930s (Dunn 1940) that lower tropospheric (from the ocean surface to about 5 km [3 mi] with a maximum at 3 km [2 mi]) westward traveling disturbances often serve as the "seedling" circulations for a large proportion of tropical cyclones over the North Atlantic Ocean. Riehl (1945) helped to substantiate that these disturbances, now known as African easterly waves, had their origins over North Africa. While a variety of mechanisms for the origins of these waves were proposed in the next few decades, it was Burpee (1972) who documented that the waves were being generated by an instability of the African easterly jet. (This instability - known as baroclinic-barotropic instability - is where the value of the potential vorticity begins to decrease toward the north.) The jet arises as a result of the reversed lower-tropospheric temperature gradient over western and central North Africa due to extremely warm temperatures over the Saharan Desert in contrast with substantially cooler temperatures along the Gulf of Guinea coast. The waves move generally toward the west in the lower tropospheric tradewind flow across the Atlantic Ocean. They are first seen usually in April or May and continue until October or November. The waves have a period of about 3 or 4 days and a wavelength of 2000 to 2500 km [1200 to 1500 mi], typically (Burpee 1974). One should keep in mind that the "waves" can be more correctly thought of as the convectively active troughs along an extended wave train. On average, about 60 waves are generated over North Africa each year, but it appears that the number that is formed has no relationship to how much tropical cyclone activity there is over the Atlantic each year.While only about 60% of the Atlantic tropical storms and minor hurricanes ( Saffir-Simpson Scale categories 1 and 2) originate from easterly waves, nearly 85% of the intense (or major) hurricanes have their origins as easterly waves (Landsea 1993). It is suggested, though, that nearly all of the tropical cyclones that occur in the Eastern Pacific Ocean can also be traced back to Africa (Avila and Pasch 1995).It is currently completely unknown how easterly waves change from year to year in both intensity and location and how these might relate to the activity in the Atlantic (and East Pacific).Date 1 June 2001 SourceNOAAAuthor Chris Landsea
  • Image Wikimedia commons:
  • NASA image
  • A and C
  • Have your students describe what they see in this graphic NOAA Photo Library] {{w:Storm surge}} during {{w:HurricaneEloise|Hurricane Eloise}}
  • structure. Image courtesy NOAA, but taken from NASA Earth Observatory website.
  • storm surge. Graphic by Robert Simmon, NASA GSFC.
  • This imageis in public domain under the terms of Title 17, Chapter 1, Section 105 of the US Code.
  • TIME?Can end with next slide, or go 15 moreLets do this again another day, too?
  • Class 1 powerpoint

    1. 1. Hurricane Hazards and Society 1A. Hazard and RiskB. Hurricane formationC. Comparing hurricanes and seasons
    2. 2. A. Hazard or Risk? 1. In this cartoon, what are the hazards? 2. How could the person minimize her risk from these hazards?
    3. 3. Geologic Hazard• Phenomenon capable of causing harm to humans – Tsunami Primary Hurricane Hazards - Wind – Flood - Storm Surge - Rain – Volcanic ash - Waves – Lahar Secondary Hurricane Hazards – Fire (caused by a primary hazard) - Flooding – Liquefaction - Fire - Landslides – Landslide - Coastal Erosion …. Can you think of others?
    4. 4. RiskThe likelihood of a hazard happening to YOUFactors:• Cost – human life – damage to property and infrastructure• Probability – dependent on location – large events are generally less likely than small ones Recall: Question for today…
    5. 5. B. Hurricane Formation:Ocean and atmosphere systems interact to create hurricanes
    6. 6. What is a hurricane?• Make a list of hurricane characteristics:
    7. 7. What is a hurricane?• Formal definition:An intense low pressure system with sustainedwinds >74 mph
    8. 8. What makes a hurricane?• 4 essential ingredients
    9. 9. What makes a hurricane?1) Warm SST >26.5°C (80°F) over large area
    10. 10. What makes a hurricane?1) Warm SST (>26.5 C) over large area2) Instability in atmosphere (rising air mass)
    11. 11. What makes a hurricane?1) Warm SST (>26.5 C) over large area2) Instability in atmosphere (rising air mass)3) Little/no vertical wind shear through troposphere (Klotzbach and Gray, 2010)
    12. 12. What makes a hurricane?1) Warm SST (>26.5 C) over large area2) Instability in atmosphere (rising air mass)3) Little/no vertical wind shear through troposphere4) Sufficient latitude >5-10o off equator
    13. 13. Hurricanes are powered by• latent heat stored in water vapor Feedback between the ocean and – released when water condenses atmosphere systems! 1. Warm water supplies sensible heat & humidity to overlying air 2. Air decreases density; rises 3. Air cools; H2Ovapor condenses 4. Latent heat released -- Heat warms air; rises faster 5. P gradient increases -- Faster winds -- More water vapor into system!
    14. 14. So… Can hurricanes cross the equator?• Discuss with the person next to you.• Why or why not?
    15. 15. Can hurricanes cross the equator? – Discuss with the person next to you. – Why or why not? (Hurricane tracks 1851-2012; NASA)
    16. 16. North Atlantic Hurricane Season is June-November Most storms occur in which month? 4 3.5 Tropical StormsAverage number per month, 1851- 3 Hurricanes 2.5 Hurricanes w/US Landfall 2 1.5 2011 1 0.5 0
    17. 17. Which of these things would cause a hurricane to lose energy?a) Moving over colder waterb) Moving over warmer waterc) Making landfalld) Crossing the ocean
    18. 18. As a hurricane approaches land
    19. 19. Wind and rain
    20. 20. Storm surge
    21. 21. As hurricanes make landfall, they decrease in strength Why? Remember what fuels hurricanes… Warm water!
    22. 22. Draw:• the relationships between the ocean, atmosphere, and people in a hurricane SummaryHazard and riskWhat is a hurricane? - What 4 conditions are necessary for hurricane formation? - What happens as hurricanes approach land?