1. Class #22: October 20, 20101 Class #22: Wednesday, October 20, 2010 Fronts And Extratropical Cyclones

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 22, 20102

3. Sank on Day 3 Class #23: October 22, 20103 Fig. 10-1, p. 276

4. Ore freighter Edmund Fitzgerald Class #23: October 22, 20104 Fig. 10-2, p. 277

5. North is at lower right. Ship sank near Whitefish Point Class #23: October 22, 20105 Fig. 10-4, p. 278

6. Day 1 and Day 2 Class #23: October 22, 20106 Table 10-1a, p. 279

7. Table 10-1b, p. 279 7Class #23: October 22, 2010

8. Day 1 weather maps: Low forms NE of Amarillo, TX Class #23: October 22, 20108 Fig. 10-5, p. 280

9. Birth to NW of Amarillo Class #23: October 22, 20109 Fig. 10-5a, p. 280

10. Strong westerlies upstream Class #23: October 22, 201010 Fig. 10-5b, p. 280

11. Low humidity, clear skies Class #23: October 22, 201011 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 22, 201012 Fig. 10-6, p. 281

13. Fig. 10-6a, p. 281 13Class #23: October 22, 2010

14. Fig. 10-6b, p. 281 14Class #23: October 22, 2010

15. Fig. 10-6c, p. 281 15Class #23: October 22, 2010

16. Shows Panhandle hook path Class #23: October 22, 201016 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 22, 201017

18. Cyclonic spin (or vorticity) is important for cyclogenesis. Class #23: October 22, 201018 Box 10-1, p. 282

19. Cyclonic spin is generated by flow over mountains Class #23: October 22, 201019 Box 10-1, p. 283

20. Day 2: Young adult stage Class #23: October 22, 201020 Fig. 10-7, p. 285

21. Note fronts, Low, and path. Ship sets sail at 2 p.m. Class #23: October 22, 201021 Fig. 10-7a, p. 285

22. Note upper-level short-wave trough to west of surface Low Class #23: October 22, 201022 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 22, 201023

24. Satellite picture from 10:12 a.m. Note the comma shape of cloud Class #23: October 22, 201024 Fig. 10-7c, p. 285

25. A close-up of last slide Class #23: October 22, 201025 Fig. 10-8, p. 286

26. Fig. 10-9, p. 287 26Class #23: October 22, 2010

27. Fig. 10-10, p. 288 27Class #23: October 22, 2010

28. Fig. 10-10a, p. 288 28Class #23: October 22, 2010

29. Fig. 10-10b, p. 288 29Class #23: October 22, 2010

30. Fig. 10-10c, p. 288 30Class #23: October 22, 2010

31. Fig. 10-11, p. 289 31Class #23: October 22, 2010

32. Fig. 10-12, p. 290 32Class #23: October 22, 2010

33. Fig. 10-13, p. 291 33Class #23: October 22, 2010

34. Fig. 10-14, p. 292 34Class #23: October 22, 2010

35. Fig. 10-14a, p. 292 35Class #23: October 22, 2010

36. Fig. 10-14b, p. 292 36Class #23: October 22, 2010

37. Fig. 10-14c, p. 292 37Class #23: October 22, 2010

38. Box 10-2, p. 293 38Class #23: October 22, 2010

39. Box 10-2, p. 293 39Class #23: October 22, 2010

40. Fig. 10-15, p. 294 40Class #23: October 22, 2010

41. Fig. 10-16, p. 295 41Class #23: October 22, 2010

42. Fig. 10-17, p. 295 42Class #23: October 22, 2010

43. Box 10-3, p. 297 43Class #23: October 22, 2010

44. Box 10-3, p. 297 44Class #23: October 22, 2010

45. Box 10-3, p. 298 45Class #23: October 22, 2010

46. Box 10-3, p. 298 46Class #23: October 22, 2010

47. Box 10-3, p. 299 47Class #23: October 22, 2010

48. Box 10-3, p. 299 48Class #23: October 22, 2010

49. Fig. 10-18, p. 301 49Class #23: October 22, 2010

50. Fig. 10-18a, p. 301 50Class #23: October 22, 2010

51. Fig. 10-18b, p. 301 51Class #23: October 22, 2010

52. Fig. 10-18c, p. 301 52Class #23: October 22, 2010