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[[Image:Katrina.jpg|right|250px|thumb|Hurricane Katrina approaching [[New Orleans]].]]

[[Image:Katrina.jpg|right|250px|thumb|Hurricane Katrina approaching [[New Orleans]].]]

A '''tropical cyclone''' is a powerful, rotating [[storm]] that begins over a warm [[ocean]]. Tropical cyclones form in [[water]]s near the [[equator]], and then they move north.  The term '''hurricane''' denotes a tropical cyclone whose maximum sustained wind speed is at least 74 miles per hour.

A '''tropical cyclone''' is a powerful, rotating [[storm]] that begins over a warm [[ocean]]. Tropical cyclones form in [[water]]s near the [[equator]], and then they move north.  The term '''hurricane''' denotes a tropical cyclone whose maximum sustained wind speed is at least 74 miles per hour.  Less severe tropical cyclones are known as tropical storms or tropical depressions, depending on intensity.

Hurricane [[wind]]s swirl about the [[eye]], a calm area in the center of the storm. The band of tall, dark clouds surrounding the eye is called the eyewall. The eye is usually 10 to 40 miles in diameter and is free of [[rain]] and large [[cloud]]s. In the eyewall, large changes in [[pressure]] create the hurricane's strongest winds. These winds can reach nearly 200 mph. Damaging winds may extend 250 miles from the eye.

Hurricane [[wind]]s swirl about the [[eye]], a calm area in the center of the storm. The band of tall, dark clouds surrounding the eye is called the eyewall. The eye is usually 10 to 40 miles in diameter and is free of [[rain]] and large [[cloud]]s. In the eyewall, large changes in [[pressure]] create the hurricane's strongest winds. These winds can reach nearly 200 mph. Damaging winds may extend 250 miles from the eye.

Hurricanes are most common during the [[summer]] and early [[Autumn| fall]]. In the [[Atlantic]] and the Northeast [[Pacific]], for example, [[August]] and [[September]] are the peak hurricane months. Typhoons occur throughout the year in the Northwest Pacific but are most frequent in summer. Approximately 85 hurricanes, typhoons, and tropical [[cyclone]]s occur in a year throughout the world.  

Hurricanes are most common during the [[summer]] and early [[Autumn| fall]]. In the [[Atlantic]] and the Northeast [[Pacific]], for example, [[August]] and [[September]] are the peak hurricane months. Typhoons occur throughout the year in the Northwest Pacific but are most frequent in summer. Approximately 85 hurricanes, typhoons, and tropical [[cyclone]]s occur in a year throughout the world.  

==Hurricane conditions==

==Hurricane conditions==

Since [[air]] tends to move from areas of high pressure to areas of low pressure, creating wind. In the Northern Hemisphere, the earth's rotation causes the wind to swirl into a low-pressure area in a [[counterclockwise]] direction. This effect of the rotating earth on wind flow is called the [[Coriolis effect]]. The Coriolis effect increases in intensity farther from the equator. To produce a hurricane, a low-pressure area must be more than 5 degrees of latitude north of the equator. Hurricanes seldom occur closer to the equator. For a hurricane to develop, there must be little wind shear, or in other words, little difference in [[speed]] and direction between winds at upper and lower elevations. Uniform winds enable the warm inner core of the storm to stay intact. The storm would break up if the winds at higher elevations increased markedly in speed, changed direction, or both. The wind shear would disrupt the budding hurricane by tipping it over or by blowing the top of the storm in one direction while the bottom moved in another direction.

Since [[air]] tends to move from areas of high pressure to areas of low pressure, creating wind. In the Northern Hemisphere, the earth's rotation causes the wind to swirl into a low-pressure area in a [[counterclockwise]] direction. This effect of the rotating earth on wind flow is called the [[Coriolis effect]]. The Coriolis effect increases in intensity farther from the equator. To produce a hurricane, a low-pressure area must be more than 5 degrees of latitude north of the equator. Hurricanes seldom occur closer to the equator. For a hurricane to develop, there must be little wind shear, or in other words, little difference in [[speed]] and direction between winds at upper and lower elevations. Uniform winds enable the warm inner core of the storm to stay intact. The storm would break up if the winds at higher elevations increased markedly in speed, changed direction, or both. The wind shear would disrupt the budding hurricane by tipping it over or by blowing the top of the storm in one direction while the bottom moved in another direction.

== External links ==

 

 

==== External links ====

*[http://www.nhc.noaa.gov/ National Hurricane Center]

*[http://www.nhc.noaa.gov/ National Hurricane Center]