Cyclones are caused by atmospheric disturbances around a low-pressure area distinguished by swift and often destructive air circulation.
A tropical cyclone is a warm-core, low pressure system without any "front" attached,
that develops over the tropical or subtropical waters, and has an organized circulation.
There are several favorable environmental conditions that must be in place before a tropical cyclone can form. They are: 1. Warm ocean waters (at least 80°F / 27°C) throughout a depth of about 150 ft. (46 m). 2.An atmosphere which cools fast enough with height such that it is potentially unstable to moist convection. 3.Relatively moist air near the mid-level of the troposphere (16,000 ft. / 4,900 m). 4.Low values (less than about 23 mph / 37 km/h) of vertical wind shear between the surface and the upper troposphere.
Vertical wind shear is the change in wind speed with height.
Tropical cyclone formation basins
Given that sea surface temperatures need to be at least 80°F (27°C) for tropical cyclones form, it is natural that they form near the equator.
However, with only the rarest of occasions, these storms do not form within 5° latitude of the equator.
This is due to the lack of sufficient Coriolis force, the force that causes the cyclone to spin.
With the above criteria, there are seven regions around the world where tropical cyclones are likely to form.
