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

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

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

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

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

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

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

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

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

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

Low humidity, clear skies Class #23: October 22, Fig. 10-5c, p. 280

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, Fig. 10-6, p. 281

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

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

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

Shows Panhandle hook path Class #23: October 22, Fig. 10-6d, p. 281

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,

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

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

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

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

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

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,

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

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

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

Fig , p Class #23: October 22, 2010

Fig a, p Class #23: October 22, 2010

Fig b, p Class #23: October 22, 2010

Fig c, p Class #23: October 22, 2010

Fig , p Class #23: October 22, 2010

Fig , p Class #23: October 22, 2010

Fig , p Class #23: October 22, 2010

Fig , p Class #23: October 22, 2010

Fig a, p Class #23: October 22, 2010

Fig b, p Class #23: October 22, 2010

Fig c, p Class #23: October 22, 2010

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

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

Fig , p Class #23: October 22, 2010

Fig , p Class #23: October 22, 2010

Fig , p Class #23: October 22, 2010

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

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

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

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

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

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

Fig , p Class #23: October 22, 2010

Fig a, p Class #23: October 22, 2010

Fig b, p Class #23: October 22, 2010

Fig c, p Class #23: October 22, 2010