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Class #23: Friday October 23

Class #23: Friday October 23. The Extratropical or Midlatitude Cyclone. The story of an extratropical cyclone. Day 1, Sat., Nov. 8,1975: Low (Panhandle Hook) forms just NE of Amarillo Day 2, Sun., Nov. 9: Ship sails at 2 p.m.; Storm has matured to young adult stage

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Class #23: Friday October 23

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  1. Class #23: Friday October 23 The Extratropical or Midlatitude Cyclone Class #23: October 23

  2. The story of an extratropical cyclone • Day 1, Sat., Nov. 8,1975: Low (Panhandle Hook) forms just NE of Amarillo • Day 2, Sun., Nov. 9: Ship sails at 2 p.m.; Storm has matured to young adult stage • Day 3, Mon., Nov. 10: The storm is occluding. Ship sinks at 7:20 p.m. • Day 4, Tues., Nov. 11: The storm is dying • Subtract 7 from date to get Day # Class #23: October 23

  3. Sank on Day 4 Class #23: October 23 Fig. 10-1, p. 276

  4. Ore freighter Edmund Fitzgerald Class #23: October 23 Fig. 10-2, p. 277

  5. North is at lower right. Ship sank near Whitefish Point Class #23: October 23 Fig. 10-4, p. 278

  6. Day 1 and Day 2 Class #23: October 23 Table 10-1a, p. 279

  7. Class #23: October 23 Table 10-1b, p. 279

  8. Day 1 weather maps: Low forms NE of Amarillo, TX Class #23: October 23 Fig. 10-5, p. 280

  9. Birth to NW of Amarillo Class #23: October 23 Fig. 10-5a, p. 280

  10. Strong westerlies upstream Class #23: October 23 Fig. 10-5b, p. 280

  11. Low humidity, clear skies Class #23: October 23 Fig. 10-5c, p. 280

  12. Typical cyclone paths • Depend on topography • Depend on position of the polar front • Depend on upper level winds: • Extratropical cyclones move approximately with the 500mb wind at about half the speed Class #23: October 23 Fig. 10-6, p. 281

  13. Class #23: October 23 Fig. 10-6a, p. 281

  14. Class #23: October 23 Fig. 10-6b, p. 281

  15. Class #23: October 23 Fig. 10-6c, p. 281

  16. Shows Panhandle hook path Class #23: October 23 Fig. 10-6d, p. 281

  17. Ingredients for a cyclone • Cyclone growth is called cyclogenesis • Cyclogenesis requires 3 ingredients: • Surface temperature gradients: a front • A strong jet stream: helps the low grow and the fronts intensify • Mountains or other surface boundaries (for example, a coastline along a warm ocean current • Cyclones get their energy in a process called baroclinic instability—related to horizontal temperature gradients and vertical wind shear Class #23: October 23

  18. Cyclonic spin (or vorticity) is important for cyclogenesis. Class #23: October 23 Box 10-1, p. 282

  19. Cyclonic spin is generated by flow over mountains Class #23: October 23 Box 10-1, p. 283

  20. Day 2: Young adult stage Class #23: October 23 Fig. 10-7, p. 285

  21. Note fronts, Low, and path. Ship sets sail at 2 p.m. Class #23: October 23 Fig. 10-7a, p. 285

  22. Note upper-level short-wave trough to west of surface Low Class #23: October 23 Fig. 10-7b, p. 285

  23. Back to the story • The cyclone moves very rapidly, steered by the upper-level winds at 500mb. • On Day 2 (Nov. 9) gale warnings were issued in the mid-afternoon for the next day (Monday, Day 3, Nov. 10) • Gale warnings are for winds up to 38 knots (44 mph), not typical, not too unusual • Ships take the northern, longer route Class #23: October 23

  24. Satellite picture from 10:12 a.m.Note the comma shape of cloud Class #23: October 23 Fig. 10-7c, p. 285

  25. A close-up of last slide Class #23: October 23 Fig. 10-8, p. 286

  26. Class #23: October 23 Fig. 10-9, p. 287

  27. Class #23: October 23 Fig. 10-10, p. 288

  28. Class #23: October 23 Fig. 10-10a, p. 288

  29. Class #23: October 23 Fig. 10-10b, p. 288

  30. Class #23: October 23 Fig. 10-10c, p. 288

  31. Class #23: October 23 Fig. 10-11, p. 289

  32. Class #23: October 23 Fig. 10-12, p. 290

  33. Class #23: October 23 Fig. 10-13, p. 291

  34. Class #23: October 23 Fig. 10-14, p. 292

  35. Class #23: October 23 Fig. 10-14a, p. 292

  36. Class #23: October 23 Fig. 10-14b, p. 292

  37. Class #23: October 23 Fig. 10-14c, p. 292

  38. Class #23: October 23 Box 10-2, p. 293

  39. Class #23: October 23 Box 10-2, p. 293

  40. Class #23: October 23 Fig. 10-15, p. 294

  41. Class #23: October 23 Fig. 10-16, p. 295

  42. Class #23: October 23 Fig. 10-17, p. 295

  43. Class #23: October 23 Box 10-3, p. 297

  44. Class #23: October 23 Box 10-3, p. 297

  45. Class #23: October 23 Box 10-3, p. 298

  46. Class #23: October 23 Box 10-3, p. 298

  47. Class #23: October 23 Box 10-3, p. 299

  48. Class #23: October 23 Box 10-3, p. 299

  49. Class #23: October 23 Fig. 10-18, p. 301

  50. Class #23: October 23 Fig. 10-18a, p. 301

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