Hurricanes are unpredictable, violent and destructive. However, scientists have unraveled much about how hurricanes work, and are learning to predict them with ever-greater precision. In this article, learn how and when hurricanes occur, how they are monitored and how to prepare for one.
They are massive, violently spiraling storms that tear across both land and water, devastating nearly everything in their path. Hurricanes, the most severe type of tropical cyclone, are products of several factors--including temperature, wind and moisture--that under the right conditions, can produce some of the worst destruction known to humankind. Although hurricanes can be unpredictable, science has been able to decipher much about how they work. In this article, find out how hurricanes work, how to prepare for them and how scientists have learned to predict their movement in order to save lives.
How do hurricanes form?
Hurricanes develop out of three basic factors: a pre-existing weather disturbance with thunderstorms; warm ocean water, with a temperature of at least 80 degrees Fahrenheit that extends about 150 feet; and light upper level winds that maintain about the same speed and direction throughout the atmosphere.
Hurricanes originate from pre-existing weather disturbances, which form off the coast of Africa every three to four days. These disturbances typically take the form of tropical waves containing areas of turbulent weather. When a disturbance enters the warm ocean water, it feeds off heat from within the ocean. Winds near the water’s surface merge with the weather disturbance, and as the air rises, the ocean’s warmth creates moisture and heat that fuel the developing storm. The moisture is condensed into drops, generating additional heat and giving more energy to the storm. Thunderstorms form, and if the wind stays light, the storm can organize and gather strength.
As it first forms, the storm is relatively unorganized, but as it strengthens, it takes on a spiral shape, and becomes what is called a tropical depression. Once the storm reaches 39 miles per hour, it is considered a tropical storm, and if winds reach at least 74 miles per hour, it is considered a hurricane. It is at this time that the storm develops what is called the eye, a cloudless area in the middle of the storm that develops as air at the center sinks, dries and creates warmth.
As hurricanes move onto land or cooler water, they are deprived of the warmth they need to maintain their structure, and begin to disintegrate. Usually, landfall robs the storm of moisture and causes it to weaken. Even as they fall apart, however, hurricanes can still be dangerous.
Tropical cyclones can also form out of the tail end of a cold front or from an upper-level low, but still need warm ocean waters in order to organize into a hurricane.