The Anatomy of a Hurricane


Indigenous tribes of Central America recognized and feared the evil god Huracan who wreaked devastation upon them time and again. In truth, a hurricane in its life span can produce more power than ten thousand nuclear bombs. The Cantonese TAI-FUNG or typhoon scourges the Western Pacific and China Sea area. In India and Australia they are known as cyclones. The scientific name for these storms is “tropical cyclone.” Spinning air that rotates around a central point of low pressure in areas of high humidity, light winds and warm surface temperatures. With water temperatures about 80 degrees Fahrenheit, it becomes a perfect spawning ground in the North Atlantic & North Pacific regions in summer and fall.

Usually, the first appearance of thunderstorms over the tropical Atlantic are a product of the African easterly wave, an area of disturbed weather that travels from East to West, carrying in its interior, warm air from the Sahara desert and the cooler air contained in the jet stream miles above the surface. The depth and breadth of the tropical cyclone deepens as the storm becomes more organized. Barometric pressure falls, and the wind begins rotating in a cyclonic circulation (counter-clockwise) in the Northern Hemisphere.

Hurricanes intensify when condensation of water vapor in rising air releases heat energy into the storm, setting off a chain reaction. The heat makes air rise even further, and the surrounding cooler atmosphere sinks to the surface, pushed down by the rising hotter air. Then this cooler air warms from the surface temperature and begins to spin upwards, winds intensify, drawing even more moisture and heat from the ocean surface. The chain reaction is now in progress.

The lower the surface pressure, the more rapidly air flows into the system and increases wind velocity, causing more thunderstorms. These release more heat, and on and on the chain is connected. The spiraling hurricane is given its distinctive shape by the earth’s rotation. Tropical depression carries 23 MPH winds, at 39 MPH it is given a name and is a tropical storm, at 74 MPH it becomes a full fledged hurricane. Ringing the eye of a mature storm is the eye wall, containing tall thunderstorms that produce heavy rains and very strong winds. As the storm moves toward land, the storm disperses heavy rains, strong winds and tornadoes. In addition, the final knockout punch comes from its dreaded storm surge, causing ocean levels to rise more than 30 feet above normal. If this coincides with the region’s normal high tide, the results are cataclysmic.

Some factors can derail a hurricane. One might be a semi-permanent high pressure system in the subtropical regions. The high pressure pushes toward the ocean surface creating a temperature inversion, a stable layer that blocks air from rising which cause thunderstorms. In addition, if the storm happens to move over cooler surface water that cannot supply the warm moist tropical air necessary to create the thunderstorms, the system will dissipate. Finally, if the storm crosses land, the lack of warm moisture to feed and develop the cyclone will scatter its contents.

Source: NASA Reference 2006