Tropical cyclone

A tropical cyclone is a rapidly rotating strom system characterized by a low pressure enter, a closed low-level atmospheric circulation, strong winds , and a spiral arrangement of thunderstorm that produce heavy rain. 

"Tropical" refers to the geographical origin of these systems, which form almost exclusively over tropical seas. "Cyclone" refers to their winds moving in a circle,[5] whirling round their central clear eye, with their winds blowing counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

Tropical cyclones are typically between 100 and 2,000 km (62 and 1,243 mi) in diameter.

The strong rotating winds of a tropical cyclone are a result of the conservation of angular momentum imparted by the Earth's rotation as air flows inwards toward the axis of rotation. As a result, they rarely form within 5° of the equator.

Tropical cyclones are areas of relatively low pressure in the troposphere, with the largest pressure perturbations occurring at low altitudes near the surface.

Size descriptions of tropical cyclones
ROCI (Diameter)	Type
Less than 2 degrees latitude	Very small/minor
2 to 3 degrees of latitude	Small
3 to 6 degrees of latitude	Medium/Average/Normal
6 to 8 degrees of latitude	Large
Over 8 degrees of latitude	Very large[20]

Tropical cyclones out at sea cause large waves, heavy rain, flood and high winds, disrupting international shipping and, at times, causing shipwrecks. On land, strong winds can damage or destroy vehicles, buildings, bridges, and other outside objects, turning loose debris into deadly flying projectiles. The storm surge, or the increase in sea level due to the cyclone, is typically the worst effect from landfalling tropical cyclones, historically resulting in 90% of tropical cyclone deaths.