LECTURE_20_04-22-10_Chap_15_Tornado

LECTURE_20_04-22-10_Chap_15_Tornado - Climate/weather –...

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Unformatted text preview: Climate/weather – Thunderstorms and Tornadoes Chap. 15 – Thunderstorms and Tornadoes • Tornados-General overview-Tornado development-Scale, size, and intensity – The Fujita Scale-Damage and risk Fig. 15-2, p. 398 Thunderstorms and Tornado development Cold air Warm air Warm air Fig. 15-2, p. 398 Tornadoes – OVERVIEW – Important Points T O R N A D O E S- Form in relation to large convective thunderstorms-In rare instances, tornadoes can also occur in the northeast quadrant of hurricanes.-Almost always have counterclockwise rotation (clockwise rotation is rare)-The U.S. has an unusually high number of large tornadoes (similar to thunderstorms)-Most destructive storm (in terms of loss of life and property) and the most significant natural hazard in the Midwest Fig. 15-1, p. 398 QUESTION? Compare the two areas on the map. Why does the U.S. Midwest have so many more thunderstorms/lightening and tornadoes than regions in China at the same latitude? Tornado Alley Tornadoes: Numbers of significant tornado days per year. p. 401-413 Fig. 15-24, p. 410 Fig. 10-17, p. 258 Tornadoes – OVERVIEW – Collision zone between two fronts-Cold air pushes under warm moist air along a cold front-Warm air rapidly rises over the advancing cold air mass-Produces individual thunderstorms fronts up to 25km in across-Lines of thunderstorms can be up to 1000 km long Fig. 15-2, p. 398 Thunderstorms and Tornado development Cold air Warm air Warm air REMEMBER: Convection – Heat – Density Not too different than convection in the Earth’s mantle A tornado can develop in the collision zone between two fronts, commonly in the “hook” of a rainstorm Fig. 15-13, p. 405 (pale blue). Tornado Development and convective thunderstorms Fig. 15-2, p. 398 Thunderstorms and Tornado development Cold air Warm air Warm air Thunderstorms – OVERVIEW – Important Points T O R N A D O E S D E V E L O P M E N T- Form when there is a shear in wind directions between “colliding” horizontal winds *EXAMPLE: westerly winds (aloft) colliding with southeasterly winds (surface)-Collision and wind shear can cause a rolling of horizon currents that can be dragged upward into vertical rotation by warm updraft in thunderstorms and creating a slowly rotating wall cloud often associated with Mammatus clouds (sign of unstable weather)-Vertically rotating vortex forms within wall clouds of thunderstorms and descend to form tornadoes- If you see what looks like Mammatus clouds and a wall cloud…tornadoes almost always soon to follow! Fig. 15-2, p. 398 Thunderstorms and Tornado development Cold air Warm air Warm air West wind (aloft) Southeast wind (surfa a. Wind shear, with surface winds from the southeast, and winds from the west aloft....
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This note was uploaded on 11/11/2011 for the course ISP 203 taught by Professor Paquette during the Fall '08 term at Michigan State University.

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LECTURE_20_04-22-10_Chap_15_Tornado - Climate/weather –...

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