Hurricanes, like animals and plants, have life cycles of their own. A regular tropical thunderstorm (tropical depression) in time can grow to a more intense stage by attaining a specified sustained wind speed. The progression of tropical disturbances can be seen in the three images below.
Hurricanes usually are able to live for fairly long periods of time, and can last for as long as two to three weeks. They may start off as a group of thunderstorms over ocean waters in tropical areas. Once a disturbance evolves into a tropical depression, it may take just half a day for it to advance on to the next stage of becoming a tropical storm. However, it may also not even occur at all. The same applies to the amount of time needed for a tropical storm to build into a hurricane. Atmospheric and oceanic conditions have major influence on the happening of these events. Firstly, the ocean water has to be warmer than 26.5 degrees Celsius as the heat and moisture from the water is the essential source of energy for the hurricane, as it is maintained by the vast amount of energy released by rapid condensation in the rising air. Therefore, hurricanes will lose strength rapidly if and when they travel across locations with insufficient heat and/or moisture such as over land or colder ocean waters.
Below, in this satellite image from 1995, different tropical disturbances in each stage are evident. At the far left, a tropical storm is visible, while two hurricanes are further east, between a couple of tropical depressions.
