ch15 - Jon Ahlquist Chapter 15 Hurricanes Tropical weather...

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Jon Ahlquist 9/6/2006 MET1010 Intro to the Atmosphere 1 Chapter 15: Hurricanes Structure of a hurricane Hurricane formation theories Organized convection Heat engine driven by warm ocean Stages of development Hurricane formation and movement Watches and warnings 5 point Saffir-Simpson scale for hurricane strength For more information, see the Web site for the National Hurricane Center, www.nhc.noaa.gov Tropical Weather (p. 406) ± Tropics: region between Tropic of Cancer (23.5°N) and Tropic of Capricorn (23.5°S). ± In tropics, temperature changes little during year, so no winter, spring, etc. ± Seasons marked mainly by differences in rainfall, so rainy season(s) and dry season(s) ± Near the equator, typically two rainy seasons & two dry seasons per year. Near Tropics of Cancer and Capricorn, one rainy season & one dry season per year. (Reason for this will be covered in chapter 3.) ± Tropical Easterly Waves, p. 406 Rain showers Rain showers on E side of trough •Tropical wave: slow moving (10-20 kts) trough of low pressure from east. •Low-level con- vergence is on east side of trough, so air rises, producing showers and thunderstorms. •Only a few (< 20%) of easterly waves produce hurricanes T r o u g h Figure 15.1, p. 406 Figure 15.1, p. 406 Hurricane Anatomy, pp. 406- 409 Tropical cyclone: general name for hurricane, typhoon, etc., with winds > 64 knots = 74 mph. In photo, note: •Eye: fairly clear, 10-30 miles across. •Eye wall: intense fastest winds. •Spiral rain bands •Total diameter of hurricane: several hundred miles. Figure 15.2, p. 407: Hurricane Elena in Gulf of Mexico (1985) Spiral rain band Eye Eye wall R ain free area Vertical Cross Section of Hurricane, Fig. 15.3, p. 408 Eye: sinking air; a few clouds; lowest surface pressure. Eye: sinking air; a few clouds; lowest surface pressure. Eye wall: intense thunderstorms around eye. Thunderstorms further out are not as strong. Thunderstorms further out are not as strong. Low Low -level air spirals inward (CCW in N Hem), level air spirals inward (CCW in N Hem), Air converges, particularly at eye wall, rises, causing Air converges, particularly at eye wall, rises, causing clouds & rain. Latent heat released. Air diverges clouds & rain. Air diverges outward at top, rotating CW in N Hem, sinks between outward at top, rotating CW in N Hem, sinks between thunderstorms, and warms. thunderstorms, and warms. Eye
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This note was uploaded on 07/21/2011 for the course MET 1010 taught by Professor Staff during the Fall '08 term at FSU.

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ch15 - Jon Ahlquist Chapter 15 Hurricanes Tropical weather...

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