How is Tropical Cyclone Classified

Cyclones are climatological phenomenon in which a low pressure core is surrounded by high pressure exterior. They move at a varied speed over the ocean and on landfall their speed decreases considerably and it dissipates. On the basis of the intensity (closely related to its velocity), the system is as:

Name	Wind Speed	Structure	Other Feature
Tropical Disturbance	Negligible	Slightly circular, with winds moving in from all directions.	Also called 'low pressure system
Tropical Depression	Less than 17 m/sec Less than 33 knots Less than 38 mph Less than 62 kmph	Organized system of thunderstorms and well defined circular motion of winds, but no eye formation.
Tropical Storms	17 - 33 m/second 34-63 knots 39-73 mph 62-117 kmph	Well-defined surface circulation. Definite cyclonic shape begins to form, eye is usually not present.	Assigned name at this stage, hence the stage is also called named storm
Hurricanes/ Typhoons, etc.	Average speed is more than 120 km per hour.	Eye formation with clear eye walls.	Strongest winds and thunderstorms.