A basic definition to start - Tropical Cyclone - Violent tropical storms between 200-700km in diameter with very strong winds circling a calm eye. (1)
Conditions needed - Sea temperatures to be 26 C and above. Depth of ocean at 70m. Location of 5 N/S of equator for the Coriolis* effect to take place. Low level of convergence of air in low atmosphere. Rapid outflow of air in upper atmospheric circulation. (1)
Occurrence - Latitude of 5 degrees to 20 degrees N/S of equator. Moves Westwards
Structure - Approach - Temperature falls, pressure falls, winds begin to gust, showers develop.
20-30km - Pressure decreases rapidly, 100km/h winds, cumulonimbus clouds give thunder and rain.
Eye - Period of calm, pressure very low temperature rises.
20-30km - Wind increases further, torrential rain, temperature drops further but pressure begins to rise.
Move away - Pressure and temperature rise, rain decreases, sunny intervals, winds drop.
Overall - It happens when warm air from the ocean rises and mixes with cool air above it. This produces storm clouds, rain, and strong swirling winds. When the winds hit 74 miles per hour, the storm is considered a hurricane. (2)
* Coriolis Effect - Results from the earth's rotation causing freely moving objects to veer towards the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
(1) Access to geography - Hazards - Malcolm Skinner, 2003, p38-39
(2) Scholastic News -- Edition 4; 9/10/2012, Vol. 75 Issue 2, p4-5, 2p