Hurricanes just don’t come out of nowhere to become what they are. They go through a process of evolution that involves several different phases. These stages of tropical development can have different lengths just as in human development depending on certain environmental conditions where it is located at a particular time.
If these conditions are right, a hurricane can develop rapidly, and go through these early stages very quickly. If these conditions aren’t right, then development can be slow, or not at all. Here are the various stages of development a hurricane goes through.
Tropical Wave – These are the most common of tropical disturbances with about 100 forming each season. They lack a closed circulation, which is when there are winds in every direction. Wind speeds are less than 20 knots or 25 mph.
Tropical Depression – A wave becomes a depression when there is a presence of a closed circulation, and sustained winds are 20 knots or 25 mph. At this point, the system is still quite disorganized.
Tropical Storm – A depression becomes a tropical storm when shower and thunderstorm activity moves over the closed circulation, and sustained winds reach at least 35 knots or 39 mph. At this point, the system is capable of causing minimal damage.
Hurricane – A tropical storm becomes a hurricane when the closed circulation becomes an eye, and sustained winds reach at least 65 knots or 74 mph. At this point, the system is capable of causing significant damage.
Note: Once arriving at hurricane status, these storms continue to intensify, and their intensity is classified by Categories according to the Saffir-Simpson Scale. This scale was created by the duo of structural engineer, Herbert Saffir and meteorologist, Robert Simpson to give people a sense of how powerful hurricanes can be at certain surface pressures and wind speeds.