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Class #9: Monday, July 19 Thunderstorms and tornadoes

Class #9: Monday, July 19 Thunderstorms and tornadoes. Chapter 14. Fig. 14-CO, p. 370. Fig. 14-1, p. 372. Thunderstorms and Tornadoes. Chapter 14. Thunderstorms. A storm containing lightening and thunder; convective storms

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Class #9: Monday, July 19 Thunderstorms and tornadoes

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  1. Class #9: Monday, July 19Thunderstorms and tornadoes Chapter 14 Class #9, Monday, July 19, 2010

  2. Class #9, Monday, July 19, 2010 Fig. 14-CO, p. 370

  3. Class #9, Monday, July 19, 2010 Fig. 14-1, p. 372

  4. Thunderstorms and Tornadoes Chapter 14 Class #9, Monday, July 19, 2010

  5. Thunderstorms • A storm containing lightening and thunder; convective storms • Severe thunderstorms: one of large hail, wind gusts greater than or equal to 50kts, or tornado • Ordinary Cell Thunderstorms • Air-mass thunderstorms: limited wind sheer • Stages: cumulus, mature, dissipating • Entrainment, downdraft, gust front Class #9, Monday, July 19, 2010

  6. Class #9, Monday, July 19, 2010

  7. Class #9, Monday, July 19, 2010 Fig. 14-2, p. 373

  8. Class #9, Monday, July 19, 2010 Fig. 14-2, p. 373

  9. Class #9, Monday, July 19, 2010 Fig. 14-2, p. 373

  10. Class #9, Monday, July 19, 2010

  11. Class #9, Monday, July 19, 2010 Fig. 14-4, p. 375

  12. Thunderstorms • Multi-cell Thunderstorms • Thunderstorms that contain a number of convection cells, each in a different stage of development, moderate to strong wind shear; tilt, over shooting top • Gust Front: leading edge of the cold air out-flowing air; shelf cloud, roll cloud, outflow boundary • Micro-bursts: localized downdraft that hits the ground and spreads horizontally in a radial burst of wind; wind shear, virga Class #9, Monday, July 19, 2010

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  14. Class #9, Monday, July 19, 2010 Fig. 14-6, p. 376

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  18. Thunderstorms • Multi-cell Thunderstorms • Squall-line thunderstorms; line of multi-cell thunderstorms, pre-frontal squall-line, derecho • Meso-scale Convective Complex: a number of individual multi-cell thunderstorms grow in size and organize into a large circular convective weather system; summer, 10,000km2 Class #9, Monday, July 19, 2010

  19. Class #9, Monday, July 19, 2010 Fig. 14-10, p. 378

  20. Class #9, Monday, July 19, 2010 Fig. 14-11, p. 378

  21. Stepped Art Class #9, Monday, July 19, 2010 Fig. 14-11, p. 378

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  27. Class #9, Monday, July 19, 2010

  28. Thunderstorms • Supercell thunderstorms • Large, long-lasting thunderstorm with a single rotating updraft • Strong vertical wind shear • Outflow never undercuts updraft • Classic, high precipitation and low precipitation supercells • Cap and convective instability • Rain free base, low-level jet • Surface, 850mb, 700mb, 500mb, 300mb conditions Class #9, Monday, July 19, 2010

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  30. Class #9, Monday, July 19, 2010

  31. Class #9, Monday, July 19, 2010

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  34. Class #9, Monday, July 19, 2010 Fig. 14-23, p. 384

  35. Thunderstorms • Thunderstorms and the Dryline • Sharp, horizontal change in moisture • Thunderstorms form just east of dryline • cP, mT, cT • Floods and Flash Floods • Flash floods rise rapidly with little or no advance warning; many times caused by stalled or slow thunderstorm • Large floods can be created by training of storm systems, Great Flood of 1993 Class #9, Monday, July 19, 2010

  36. Class #9, Monday, July 19, 2010 Fig. 1, p. 386

  37. Class #9, Monday, July 19, 2010

  38. Thunderstorms • Topic: Big Thompson Canyon • July 31, 1976, 12 inches of rain in 4 hours created a flood associated with $35.5million in damage and 135 deaths • Distribution of Thunderstorms • Most frequent Florida, Gulf Coast, Central Plains • Fewest Pacific coast and Interior valleys • Most frequent hail Central Plains Class #9, Monday, July 19, 2010

  39. Class #9, Monday, July 19, 2010 Fig. 14-25, p. 387

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  41. Class #9, Monday, July 19, 2010

  42. Thunderstorms • Lightening and Thunder • Lightening: discharge of electricity in mature storms (within cloud, cloud to cloud, cloud to ground) • Thunder: explosive expansion of air due to heat from lightening • Electrification of Clouds: graupel and hailstones fall through supercooled water, ice crystals become negatively charged • Upper cloud positive, bottom cloud negative Class #9, Monday, July 19, 2010

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  44. Class #9, Monday, July 19, 2010 Fig. 2, p. 390

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  46. Class #9, Monday, July 19, 2010

  47. Thunderstorms • Observations: Elves • Blue jets, red sprite, ELVES • The Lightening Stroke • Positive charge on ground, cloud to ground lightening • Stepped leader, ground stroke, forked lightening, ribbon lightening, bead lightening, corona discharge Class #9, Monday, July 19, 2010

  48. Class #9, Monday, July 19, 2010

  49. Thunderstorms • Observation: Apple tree • DO NOT seek shelter during a thunderstorm under an isolated tree. • Lightening Detection and Suppression • Lightening direction finder detects radiowaves produced by lightening, spherics • National Lightening Detection Network • Suppression: seed clouds with aluminum Class #9, Monday, July 19, 2010

  50. Class #9, Monday, July 19, 2010

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