1. Chapter 10

2. Thunderstorms  A storm containing lightning 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

3. Fig. 10-1, p. 275

4. Fig. 10-2, p. 276

5. Fig. 10-2a, p. 276

6. Fig. 10-2b, p. 276

7. Fig. 10-2c, p. 276

8. Stepped Art Fig. 10-2, p. 276

9. Fig. 10-3, p. 277

10. 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

11. Fig. 10-4, p. 278

12. Fig. 10-5, p. 278

13. Fig. 10-6, p. 279

14. Fig. 10-7, p. 279

15. Fig. 10-8, p. 280

16. Fig. 10-9, p. 280

17. Fig. 10-10, p. 281

18. Fig. 10-11, p. 281

19. Stepped Art Fig. 10-11, p. 281

20. Thunderstorms  Mutli-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, 10,000km 2

21. Fig. 10-12, p. 282

22. Fig. 10-13, p. 282

23. Fig. 10-14, p. 282

24. Fig. 10-15, p. 283

25. Fig. 10-16, p. 283

26. 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

27. Fig. 10-17, p. 284

28. Fig. 10-18, p. 284

29. Fig. 10-19, p. 285

30. Fig. 10-20, p. 285

31. 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

32. Fig. 10-21, p. 286

33. Fig. 10-22, p. 287

34. 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

35. Fig. 10-23, p. 289

36. Fig. 10-24, p. 289

37. Thunderstorms  Lightning and Thunder Lightning: discharge of electricity in mature storms (within cloud, cloud to cloud, cloud to ground) Thunder: explosive expansion of air due to heat from lightning Electrification of Clouds: graupel and hailstones fall through supercooled water, ice crystals become negatively charged Upper cloud positive, bottom cloud negative

38. Fig. 10-25, p. 290

39. Fig. 10-26, p. 291

40. Fig. 10-27, p. 291

41. Thunderstorms  Types of lightning Blue jets, red sprite, ELVES  The Lightning Stroke Positive charge on ground, cloud to ground lightning Stepped leader, ground stroke, forked lightning, ribbon lightning, bead lightning, corona discharge

42. Fig. 10-28, p. 292

43. Fig. 10-28a, p. 292

44. Fig. 10-28b, p. 292

45. Fig. 10-28c, p. 292

46. Fig. 10-29, p. 293

47. Fig. 10-30, p. 294

48. Fig. 10-31, p. 294

49. Fig. 10-32, p. 295

50. Thunderstorms  Lightning Detection and Suppression Lightning direction finder detects radiowaves produced by lightning, spherics National Lightning Detection Network Suppression: seed clouds with aluminum  Observation: Apple tree DO NOT seek shelter during a thunderstorm under an isolated tree.

51. Fig. 10-33, p. 295

52. Tornadoes  Rapidly rotating column of air that blows around a small area of intense low pressure with a circulation that reaches the ground.  Tornado life cycle Organizing, mature, shrinking, decay stage

53. Fig. 10-34, p. 297

54. Tornadoes  Tornado Occurrence US experiences most tornadoes Tornado Alley (warm, humid surface; cold dry air aloft) Highest in spring, lowest in winter  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  Tornado outbreaks Families, super outbreak

55. Fig. 10-35, p. 298

56. Fig. 10-36, p. 298

57. Fig. 10-37, p. 299

58. Fig. 10-38, p. 299

59. Fig. 10-39, p. 301

60. Tornados  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

61. Table 10-1, p. 300

62. Table 10-2, p. 301

63. Table 10-3, p. 301

64. Tornadic Formation  Basic requirements are an intense thunderstorm, conditional instability, and strong vertical wind sheer  Supercell Tornadoes Wind sheer causes spinning vortex tube that is pulled into thunderstorm by the updraft Mesocyclone, BWER, rear flank downdraft, vertical stretching, funnel cloud, rotating cloud, wall cloud

65. Fig. 10-41, p. 303

66. Fig. 10-42, p. 303

67. Fig. 10-42a, p. 303

68. Fig. 10-42b, p. 303

69. Stepped Art Fig. 10-42, p. 303

70. Fig. 10-43, p. 304

71. Fig. 10-44, p. 304

72. Tornadic Formation  Nonsupercell Tornadoes Gustnadoes Land spout Cold-air funnels

73. Fig. 10-45, p. 305

74. Fig. 10-46, p. 306

75. Fig. 10-47, p. 306

76. Fig. 10-47a, p. 306

77. Fig. 10-47b, p. 306

78. Observing Tornadoes and Severe Weather  Doppler radar measures the speed of precipitation toward and away radar unit  Two Doppler radars can provide a 3D view  TVS, doppler lidar  NEXRAD

79. Fig. 10-48, p. 307

80. Fig. 10-49, p. 308

81. Waterspouts  Rotating column of air that is connected to a cummuliform cloud over a large body of water  Tornadic waterspout

82. Fig. 10-50, p. 308