Late September Hurricane Watch: Sanba, Lane, Kristy and Nadine

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Tropical Storm Kristy and Hurricane Lane: Image courtesy of NASA

Stormy Terminology

During the Pacific and Atlantic hurricane seasons, the words cyclone, hurricane, typhoon, and tropical storm move about with great rapidity, leaving storm-watchers dizzy with terminology. The general name for all of these storms is a tropical cyclone – a cyclone occurs when warm air moves upward from the ocean’s surface.  The wind in a cyclone moves around a central low-pressure area.

The Development of a Tropical Cyclone

Like other natural phenomena, tropical cyclones have a life cycle. They form, they gain strength, they lose strength, and then they taper off and ultimately stop.  The beginning of a tropical cyclone is a tropical depression, a cyclone with winds of less than 39 mph. After the storm exceeds wind speeds of 39 mph, it is called a tropical storm. For a storm to graduate into a full tropical cyclone, it must have winds that are 74 mph or more.

Cyclone Terms Vary From Place to Place

When a storm becomes stronger than 74 mph, the name for the storm varies according to its location in the world. As a general rule, “hurricanes” occur in the Americas, in the North Atlantic and Northeast Pacific, while “typhoons” occur in the Northwest Pacific, in storms that hit Asia’s shores. In the Indian Ocean, however, these storms are actually called “cyclones” or cyclonic storms.

Cyclone Formation and Disintegration

Tropical cyclones also have categories that are based on the wind speed of the storm. All cyclones are different, and some never make it beyond a Category One level. While these categories can give an estimate of the damage expected from a storm, the actual damage varies greatly depending on the structures where the hurricane makes landfall and the length of time that it stays in an area. Once the cyclone no longer has the characteristics of a cyclone and begins to disintegrate, it is called a post-tropical cyclone.

Understanding Cyclones

Cyclone-speak can make the average storm watcher’s head spin. Just remember – it’s the intensity of the wind in a storm that determines whether the storm is a cyclone or not, and it is the location of the storm that determines what people will actually call it.

References

NASA. Hurricane Resource Page. (2012). Accessed September 20, 2012.

National Hurricane Center. Glossary of NHS Terms. (2012). Accessed September 20, 2012.

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