Tropical cyclones form when ambient atmospheric conditions are ripe for storm development, which includes warm ocean waters, moist mid-tropospheric layers, proximity to the equator and the presence of a pre-existing atmospheric disturbance. Humidity, adequate ocean water temperatures and strong winds all help to make cyclones form, but these elements must converge to allow storms to take shape. After forming, cyclones develop an organized inner core, which is surrounded by a circular mass that spins.
One of the key elements to the formation of cyclones is the right temperature of surrounding waters. Water temperatures must be at least 80 degrees Fahrenheit for cyclones to take shape, and that temperature must usually remain constant 150 feet below the surface of the water. In addition to warm ocean waters, cyclones need ideal atmospheric conditions from the skies above. Atmospheres must cool quickly and be slightly unstable, which allows for the formation of thunderstorms. Cyclones cannot form without sufficient amounts of moisture in the mid-tropospheric layer, as moisture is essential for the formation of thunderstorms.
Cyclones must also be situated proximately to the equator, with a distance no greater than 300 miles from the equator line. Within this area, the Coriolis force can take effect by allowing wind balance to occur that, in turn, helps cyclones maintain a low pressure.