In some ways hurricanes behave like living creatures and they too have a life cycle. They are born, grow to full size and strength and then fade away. Their lifespan, including all stages of the cycle, can last a considerable time. Some hurricane live for two weeks or longer.
Birth
Tropical depressions can give birth to hurricanes. Tropical depressions form from a group of thunderstorms and are regions of very low atmospheric pressure. Thunderstorms themselves form as warm, damp air rises which is the reason they are especially common during the summer.
Tropical depressions show the signs of rotation, wind, and rain that categorise hurricanes but may or may not develop further. Wind speeds in a tropical depression are usually quite slow being in the region of 20-40 miles per hour.
Development
Given the right conditions things can intensify and this is when the depression grows first into a tropical storm. Tropical storms show wind speeds of 39 to 73 miles per hour and this is when meteorologists assign names.
This practice began properly in 1953 and is not simply anthropomorphism. When discussing important weather events whose development needs to be tracked, particular over the radio, names are a shorthand way of referring to them. They also prevent the possible confusion that could arise were say numbers used.
Mature stage
Not all tropical storms develop fully. Those that do are all categorised as cyclones, with the terms hurricanes and typhoons referring to the geographical location as well as the intensity. Hurricanes are cyclones forming off the North Pacific and North-east Atlantic oceans. A hurricane is defined as such once wind speeds exceed 74 miles per hour.
The mature hurricane may be a category 1 type. These lesser hurricanes are damaging but not enormously so with wind speeds ranging from 74-85 mph. At the other end of the scale are category 5 hurricanes whose wind speeds are over 155 mph. These can be catastrophic.
All hurricanes are potentially deadly. A fully developed hurricane is not something to be ignored and if you live in an area they visit then you should pay close attention to weather reports and hurricane warnings during the spring and summer months.
Dissipation
Hurricanes all eventually die. They are sustained by continually rising warm damp air. Once they move over land or into colder regions they steadily lose energy and begin to fade. This may be a long way from way they started. Hurricanes have been known to finally dissipate as far north as the coast of Scotland.
Metereologists need to know the lifecycle of a hurricane in order to predict where they are likely to be formed and where they are likely to go. Hurricanes are not of course living organisms with what we normally think of as a life cycle, but describing them in such terms can make explaining and understanding them easier.
