What is a Tropical Cyclone?
The Tropical Cyclone/Hurricane is a warm core low pressure weather system that develops over the tropical or subtropical air masses over the oceans and has an organized circulation with winds of at least 120 Kilometers per hour. In India the cyclones of wind speeds between 89 kilometers to 118 kilometers per hour are classified as Severe Cyclonic Storms (SCS).
Depending on the location, these tropical cyclones have different names. In Atlantic & eastern Pacific Oceans they are called Hurricanes while in western Pacific they are called Typhoons and in India they are called Cyclones.
Conditions necessary for Tropical Cyclone/Hurricane/Typhoon formations
First there has to be enough Coriolis or rotation force to develop a Low Pressure Center. There is no Coriolis force on Equator and +50 Latitude (about 550 kilometers) on the either side the equator. Hence no Tropical Cyclones/Hurricanes are formed in these regions.
Second there has to be sufficient warm ocean temperatures of approximately 270C at least 60 meters deep or approximately 200 feet below the surface of the ocean. So where ocean waters are very warm there are tremendous Tropical cyclone/Hurricane activity while where the oceans are cold there is paucity of Tropical Cyclone activity.
Third there has to be relatively small amounts of vertical wind shear to facilitate the continued development of the cloud systems into a Tropical Cyclone/Hurricane.
Even though all the above three necessary conditions may be met, it is entirely possible that there may not be a Tropical Cyclone/Hurricane.
When all the necessary conditions are in place, the three most triggering events for formation of Tropical Cyclones are Intertropical Convergence Zones, easterly waves or cold fronts that extend into the tropics, typically into the Tropical Cyclone/Hurricane seasons.