How Hurricanes Form

Published: 06th February 2012
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Hurricanes are extremely complicated weather systems that can only be formed when several conditions are absolutely perfect all at the same time. Even today’s top scientists don’t completely understand how hurricanes form but they do know mostly what’s necessary.

Hurricanes get their massive amounts of energy from warm, moist air. A Hurricane typically will only form when a storm passes over water that is at least 80 degrees Fahrenheit (27 degrees Celsius). In order to have enough warm water to fuel the hurricane, it should run to at least 150 feet deep (46 meters). The conditions for hurricane formation typically only between 10 and 30 degrees of the equator and the majority form between 15 and 20 degrees. They normally form off the west coast of Africa.

The warm, moist air rises off of the surface of the Atlantic, leaving a low pressure condition near the surface. Air from adjacent areas moves in to this low pressure area in a swirling motion due to the Coriolis force which is strongest near the equator. That new air is then also heated by the warm water, and also rises, adding to the energy of the hurricane. As the rising warm, moist air reaches an altitude where it begins to cool, the water in the air condenses and forms clouds. Because of the “swirling” action of the new air from adjacent areas, the cloud system begins to rotate and winds therefore increase. In addition to prevailing winds, the spinning action of hurricanes also causes them to move across the water.

As long as the storm/hurricane continues to move over warm waters, this process continues and can increase in intensity if the water temperature increases and/or the humidity in the air increases. When a hurricane moves over land it weakens due to the lack of moisture and lack of heat from the surface. While the surface of the land might actually be warmer than the water, it quickly cools just below the surface so the total available heat is much less. A hurricane can not survive with water temperatures below 79.7 degrees Fahrenheit (26.5 Celsius).

Lesser but nevertheless important factors required in the formation of hurricanes are low wind shear, high general humidity, and a pre-existing atmospheric disturbance (typically thunderstorms).

There is no doubt that hurricanes are one of the most hazardous and threatening natural forces on Earth but they do serve a useful purpose by keeping the Earth’s temperatures relatively constant by moving heat from the tropics to cooler areas to the North. Even though moving North generally results in considerable weakening, a hurricane can still retain enough power as a tropical storm to carry a huge amount of heat as far North as Canada!

You may have seen a weather report about a typhoon or a cyclone and thought that they looked exactly like a hurricane. There is actually no difference between them except their location. Hurricanes form on the west coast of Africa and move towards central America, Mexico, or the southern United States. While much rarer, hurricanes can also form in the Northeast Pacific Ocean to the east of the international dateline or in the South Pacific to the east of 160E longitude. Typhoons form in the Northwestern Pacific west of the dateline. A “Severe Tropical Cyclone” forms either in the Southeast Indian Ocean to the east of 90E longitude or in the Southwestern Pacific west of 160E longitude. A “Severe Cyclonic Storm” forms in the north Indian Ocean. Finally, a “Tropical Cyclone” forms in the southwest Indian Ocean. The only real difference between storms is that those in the northern hemisphere rotate counter-clockwise and those in the southern hemisphere rotate clockwise.

Not all hurricanes are alike, however. They are rated as category 1 through 5 storms with 1 being the weakest. A category 1 hurricane can result in a real mess due to wind and rain damage, power outages, and even deaths. A category 5 storm will nearly always totally destroy homes, take out power for weeks, and kill many thousands of people.

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