by Laura S.

Created on: November 09, 2008

While middle-latitude cyclones help transfer heat and moisture pole ward and bring colder and drier air Equator ward, Hurricanes and their counterparts in other locales all within a broad class of storms known as tropical cyclones, move incredible amounts of tropical heat and moisture toward the poles. That's because these storms from much closer to the Equator, over warm ocean waters, and typically do not have fronts associated with them until they reach higher latitudes and are in their waning phases. Hurricanes are noted for their circular, banded pattern, low-level inflow, upper-level outflow and especially their eye. They typically form and move westward within the trade wind easterlies near the Equator, and recurve to the east only when they reach middle latitudes. The transformation from a warm and humid air mass into one filled with towering cumulus clouds, generates an incredible amount of energy, If fact, according to the Atlantic Oceanographic and Meteorological Laboratory (AOML) of the National Oceanic and Atmospheric Association (NOAA), an average hurricane (one with a radius of about 400 miles (644 km)) can produce the equivalent of 200 times the world's electrical generation capacity each day. That these storms have multi-day lifetimes, and that some 70-80 occur each year around the world, truly make the hurricane the "the greatest storm on Earth". For ease in describing these more intense storms, simply refer to them as hurricanes, unless there's a specific geographical focus. Once winds in a closed tropical low-pressure system reach 39 mph, the system is named either a tropical storm or tropical cyclone depending upon its location. Then, a name is assigned according to international naming conventions. These names can be drawn from the appropriate six-year naming lists for some ocean basin and or agreed to multicultural or regional names. Names are used to help focus attention to particular storms, especially when several storms are occurring at the same time; the names also provide easy recognition for past storminess. Storms that are especially deadly or destructive have their names retired Evolving from a tropical wave, through tropical depression, to a tropical storm and finally a hurricane, tropical cyclones often capture our attention not only because of their power but also because of their wide-ranging societal, economic and physical impacts.

A storm by any other name

Tropical cyclones are the broad class of all low-pressure systems that form in the tropics and have a closed wind circulation with sustained winds of at least 39 mph (63 km/h). When sustained winds reach 74 mph (119 km/h), the storm is classified according to its geographical location:

Hurricane (The North Atlantic Ocean, the Northeast Pacific Ocean east of the dateline or the South Pacific Ocean east of 160E)

Typhoon (The Northwest Pacific Ocean west of the dateline)

Severe tropical cyclone (The southwest Pacific Ocean west of 160E or Southwest Indian Ocean east of 90E)

Severe cyclonic storm (the North Indian Ocean) or

Tropical cyclone ( the Southwest Indian Ocean)

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