 Tropical Terms"Tropical Cyclone" is a generic term for low pressure systems with a defined wind circulation, born over tropical, or sometimes subtropical, waters. Tropical depressions, tropical storms, hurricanes, and typhoons are all tropical cyclones. The term hurricane is derived from the Spanish word, huracan. In turn, the word huracan probably came from Hunraken, the Mayan storm god, or Hurakan, the Quiche god of thunder and lightning, or any of a number of other Caribbean Indian terms for evil spirits or big winds. Although the word was originally used to describe any localized tropical cyclone in the West Indies, it now classifies the powerful tropical cyclones that develop in the North Atlantic Ocean, the Gulf of Mexico, the Caribbean Sea, or the eastern North Pacific Ocean, east of the International Dateline and north of the equator. A hurricane's life cycle pass through four distinct stages, tropical disturbance, tropical depression, tropical storm and finally, a hurricane. All are classified as tropical cyclones. Tropical Disturbance A tropical disturbance is a discrete system of clouds, showers, and thunderstorms that originates in the tropics and maintains its identity for twenty-four hours or more.Tropical waves are a type of tropical disturbance. They are troughs of low pressure which move generally from east to west, imbedded in the tropical easterlies. They are also called easterly waves. Tropical DepressionWhen a tropical disturbance develops a closed circulation (counterclockwise winds blowing around a center of low pressure in the Northern Hemisphere), it is designated a tropical depression. Tropical depressions contain maximum sustained 1-minute winds at 10 meter elevation of 38 miles per hour (33 knots) or less. Tropical StormA tropical cyclone is given a name by the National Hurricane Center once it reaches tropical storm status. Tropical storms contain maximum sustained 1-minute winds at 10 meter elevation of 39 to 73 miles per hour (34 to 63 knots). HurricaneHurricanes have sustained 1-minute winds at 10 meter elevation of at least 74 miles per hour (64 knots). Winds in most hurricanes can become much stronger.Hurricanes are categorized on a scale of 1 to 5 based on their wind speed, barometric pressure, and resultant destructive potential. This is known as the Saffir-Simpson Scale, named after its originators, Herbert Saffir and Dr. Robert Simpson. Hurricanes, or their equivalents, occur in other parts of the world. In the western North Pacific Ocean, for example, they are known as typhoons. Check out when these storms are most likely to occur or how tropical forecasters predict hurricanes. | 
