Hurricanes are the most violent storms on Earth. People call these storms by other names, such as typhoons, tornadoes or cyclones, depending on where the hurricane is being formed.
The scientific term for all these storms is tropical cyclone. However, depending on their geographic location and intensity, tropical cyclones may gain several other names, such as hurricane, typhoon, tropical storm, cyclonic storm, tropical depression or simply cyclone.
Many tropical cyclones form when atmospheric conditions around a mild disturbance in the atmosphere are favorable. They occur where hot, humid air rises to high layers of the atmosphere, and cold, dry air falls back to the surface, causing the atmospheric pressure to drop to the surface.
The tropical cyclone acts like a large "vacuum cleaner", sucking air from the surface and expelling it at high altitudes.
Hurricane Katrina during its peak intensity on August 28, 2005 / USA
There is a wind speed scale to measure the categories of a cyclone. The measurement is from 1 to 5, with 5 being the most devastating.
Winds in mph
Winds in km / h
Height / m
Pressure / hPa
Greater than 980
More than 155
More than 249
More than 5.5
Less than 920
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New Orleans (Louisiana, Southern USA) after Hurricane Katrina