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The October 23 Extratropical Cyclone: A Comprehensive Analysis of Cyclogenesis

This document explores the formation and evolution of an extratropical cyclone that began on October 23. It details significant events across four days, beginning with the cyclone's birth near Amarillo, Texas, and culminating in its decline by November 11, 1975. With a focus on the atmospheric conditions that contribute to cyclogenesis, including temperature gradients and jet streams, this analysis also includes maps, satellite imagery, and warnings issued during the storm's progression, exemplifying the dynamic nature of midlatitude cyclones.

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The October 23 Extratropical Cyclone: A Comprehensive Analysis of Cyclogenesis

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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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