Origins

• Hurricanes start out as tropical storms.oahu storm from ocean image by Adam Edwards from Fotolia.com
  
  The starting point of a hurricane sounds innocent. Low pressure systems intersect with balmy ocean temperatures of at least 80 degrees Fahrenheit. These low-pressure areas keep feeding off the vapors that evaporate from the warm ocean surface, according to Weather Questions. Condensation forms clouds and then rain, spewing more warmth into the nearby air. At this point, the storm is considered to be a tropical disturbance.
  
  

Cycle

• Wind and Sunset image by Nont from Fotolia.com
  
  The heat that is released by a tropical thunderstorm escalates. This buildup of warmth causes atmospheric pressure to drop, and the wind gusts to spiral inward toward the center of the falling pressure spot. This cycle keeps repeating itself---more water evaporates, additional winds twirl near the center, extra thunderstorms set in, and more warmth radiates into the upper atmosphere. This inward spiraling is the funnel cloud.
  
  

Eyes

• hurricane image by cherry from Fotolia.com
  
  Once a funnel forms, this spinning storm hovers with a midpoint that is filled with low pressure known as the "eye" of the storm, according to National Geographic. This central area of sinking air can be 20 to 30 miles wide and is unusually calm. Outside of the "eye" is a wall of violent thunderstorms that functions like an out-of-control engine that continues to siphon its energy from the ocean's warmth.
  
  

Intensity

• Tropical Rain Storm Clouds 2 image by Jorge Moro from Fotolia.com
  
  The intensity of the tropical storm builds until it erupts into a hurricane driven by wind speeds that sometimes exceed 160 mph. A hurricane spews up to 2.4 trillion gallons of rain in a single day. This fierce storm slams onto the shoreline, creating huge mounds of water known as storm surges that climb 20 feet high and extend up to 100 miles inland. Most hurricane fatalities occur during storm surges. Hurricanes also unleash smaller tornadoes that are equally destructive.
  
  

Authorities

• Storm image by Buonfiglio from Fotolia.com
  
  Authorities label a forceful series of rain and winds as a tropical storm when speeds reach 39 mph. And when gusts hit 74 mph, the storm is upgraded to a hurricane and assigned a rating from one through five using the Saffir-Simpson scale. The National Hurricane Center tracks storms and uses information on hurricanes to issue warnings when a powerful storm shows signs of heading toward land.