8a-typhoon hurricane twister0

8a-typhoon hurricane twister0 - 32 THE SJITURDJIY EVENING...

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32 THE SJITURDJIY EVENING POST Sept./Oct. 2005 TROPICAL TWISTERS: HURRICANES A leading meterological scientist explores the forces at work in the cyclical upsurge of hurricane activity. by Dr. Roy W. Spencer / t's that time of year again. .. hurri- cane season! The news media keep us informed of the latest storm, how strong it is. where it might strike— constantly reminding us of our vul- nerability to nature's fury. With the 2005 season off to a record-breaking start and the busy 2004 season still a vivid memory, it was inevitable that scientists would renew the debate over the possible connection between the reeent upsvi^ng in the frequency of these atmospheric maelstroms and global warming. Hurrieanes are a source of end- less fascination for the public and researchers alike. The interest is not limited to the United States—our web site. WeatherStreet.com, receives visi- tors to our hurricane pages from al- most every country in the world. What causes these whirlwinds of destruction? While cyclonic storms outside of the tropics rely on air masses of different temperature for their energy, hurricanes are unique in that they extract their power from thunderstorms. Evaporation of water cools the surface of most of the Earth, a process which stores the latent heat of evaporation in the water vapor, TTiis heat is later released when clouds form and thunderstorms release mas- sive quantities of this heat, with the condensed water returning to the sur- face in the form of rainfall. Outward-spiraiing high-level winds. Descending dry air. 10-15 km high Storm moving at 15 40 km/h in direction of prevailing wind Eye (calm, very low- pressure center). Greatest windspeeds (up to 300 km/hj about 20 km from eye wall Precipitation getierates in eye wall Spiraling bands of wind and rain Warm moist air drawn in "•Water vapor picked up from seafeeds walls of cumulus clouds In a hurricane, the heat released by condensing water vapor within thunderstorm updrafts forces air around the storms to sink and warm. When wind shear is weak through the depth of the thunderstorms, this warmed air can become confined to a single area, the developing of the hurricane eye and its surroundings, rather than being blown away by high-level winds. The warmer the air be- comes, the lower the air pressure at the surface. The low pressure causes air surrounding the incipient hurricane to flow inward toward the cyclone center, evaporating more wa-
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This note was uploaded on 02/19/2011 for the course GEOG 222 taught by Professor Ngandchan during the Fall '08 term at CUHK.

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8a-typhoon hurricane twister0 - 32 THE SJITURDJIY EVENING...

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