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The Greatest Storms on Earth, Part II



The Greatest Storms on Earth, Part II
Reading Level
     edHelper's suggested reading level:   grades 6 to 9
     Flesch-Kincaid grade level:   8.84

Vocabulary
     challenging words:    deflective, forecasters, buoyancy, landfall, explosive, atmosphere, status, article, heated, entire, meteorologists, tremendous, aircraft, gain, information, vapor
     content words:    Greatest Storms, South Atlantic, South Pacific, Coriolis Effect, National Weather Service


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The Greatest Storms on Earth, Part II
By Trista L. Pollard
  

1     In the article, The Greatest Storms on Earth, Part I, you learned some background information about hurricanes. Now we will discuss how hurricanes form and decay. The easiest way to describe a hurricane is to compare it to an engine that needs continuous heat to work. For hurricanes, this heat comes from the condensation of large amounts of warm water vapor. When this water vapor is condensed, the heat is released into the air. This heated air gives the hurricane the buoyancy or lift it needs to move over oceans and land. As this process occurs, there is an area of low pressure near the surface. When there is low pressure, this means that air is rising. In the case of a hurricane, the air is rising rapidly. In contrast, areas of high pressure occur when air is sinking. Hurricanes need the warm, moist tropical air to build strength and to continue their journey across the oceans towards land.
 
2     Hurricanes usually form during the late summer months or during hurricane season. This is the time when these storms and other types of tropical storms are more likely to occur. Tropical storms are formed over warm oceans. They contain winds that blow between 39 and 73 miles per hour. If the wind increases during a tropical storm, a hurricane may develop.
 
3     Hurricanes also need an ocean water temperature of 80 degrees Fahrenheit (27 degrees Celsius) or higher before they form. Since the ocean waters of the South Atlantic and the eastern South Pacific are cooler, hurricanes are less likely to occur in those areas. Another interesting fact is that hurricanes are not "born" within 5 degrees of the equator. This is confusing since the water temperature around the equator should be high enough for hurricanes. However, there is a special condition called the Coriolis Effect that prevents hurricanes from forming near the equator. The Earth's rotation causes a deflective or repelling force to occur. This force or the Coriolis Effect acts on all moving objects including our planet's atmosphere and oceans. Since the Coriolis Effect is too weak around the equator, the winds will not gain enough speed to form a hurricane.

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