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Tornadoes

Chapter 14. Tornadoes. Oldest Known Photograph of a Tornado (1884). Tornadoes. Rapidly rotating column of air that flows around a small area of intense low pressure with a circulation that reaches the ground. Tornadoes. Table 14-2, p. 400. Tornadoes. When. F-Scale Converted to EF-Scale

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Tornadoes

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  1. Chapter 14 Tornadoes

  2. Oldest Known Photograph of a Tornado (1884)

  3. Tornadoes • Rapidly rotating column of air that flows around a small area of intense low pressure with a circulation that reaches the ground.

  4. Tornadoes

  5. Table 14-2, p. 400

  6. Tornadoes • When

  7. F-Scale Converted to EF-Scale Enhanced Fujita Scale Feb 1 2007 Wind speeds in mph, 3-second gust Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

  8. DOD to Wind Speed to EF-Scale Wind speeds in mph, 3-second gust Objectives: 3, EF-Scale structure

  9. Why the EF-Scale was created The framed house is one of only a few F-scale damage indicators. • Need more damage indicators • recalibrate winds associated with F-scale ratings • better correlate wind and rating • account for construction variability • Flexibility, Extensibility, Expandability Evidence indicates a well constructed house can be blown away by winds much less than 260 mph (Phan and Simiu,2003).

  10. Tornadoes • Tornado outbreaks • Families, super outbreak

  11. Super tornado outbreak April 3-4, 1974 315 deaths http://www.april31974.com/

  12. Palm Sunday April 11 196547 Tornadoes in 12 hours span 271 deaths, 3400 people injured 1.1 billion damage (2003 $$$$)

  13. May 3-4 1999 Oklahoma City • 66 tornadoes • 46 fatalities, 800 injured • 1.5 billion damage • An F-5 tornado • http://www.norman.noaa.gov/2000/05/first-anniversary-of-may-3-1999-tornado-outbreak-highlights-importance-of-warnings/

  14. Fig. 14-37, p. 396

  15. Tornadoes • Tornado Occurrence • US experiences most tornadoes • Tornado Alley (warm, humid surface; cold dry air aloft) • Highest occurrence spring (may June), lowest winter • Highest Death Toll , April

  16. Where else do tornadoes form?

  17. Two of the highest concentrations of tornadoes outside the U.S. are Argentina and Bangladesh. Both have similar topography with Brazil (Argentina) or from the Indian Ocean (Bangladesh). mountains helping catch low-level moisture from over Brazil (Argentina) or from the Indian Ocean (Bangladesh).

  18. Palm Sunday Tornado April 11 , 1965 271 deaths http://www.crh.noaa.gov/dtx/palmsunday/ Super tornado outbreak April 3-4, 1974 315 deaths http://www.april31974.com/

  19. http://www.tornadoproject.com/toptens/toptens.htm

  20. Radar Doppler Radar Phased array radars http://www.oar.noaa.gov/spotlite/2008/spot_radar.html

  21. Tornadoes • Tornado winds • Measurement based upon damage after storm or Doppler radar • For southwest approaching storms, winds strongest in the northeast of the storm, 220 kts maximum • Multi-vortex tornados

  22. Tornadic Formation • Basic requirements are: • an intense thunderstorm • Vertical wind shear • Cold air aloft and warm moist air near surface (unstable conditions) • Initiation of convection • Capping inversion

  23. Vertical wind shear Cold air aloft and warm moist air near surface (unstable conditions) Initiation of convection Capping inversion

  24. Tornadoes • Seeking shelter • Basement or small, interior room on ground floor • Indoor vs. outdoor pressure • The Fujita Scale • Based upon the damage created by a storm • F0 weakest, F5 strongest • Enhanced Fujita Scale

  25. Severe Weather and Doppler Radar • Doppler radar measures the speed of precipitation toward and away radar unit • Two Doppler radars can provide a 3D view • TVS, Doppler lidar • NEXRAD

  26. Waterspouts • Rotating column of air that is connected to a cumuliform cloud over a large body of water • Tornadic waterspout

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