The wind seems to get in the news a lot. A few months ago, there was wind in the form of tornadoes; soon it will be wind chill factor. Presently it’s hurricanes, but there’s more to these storms than wind.
Hurricanes (from the Taino word hurricane, meaning "evil spirit") are technically referred to as tropical cyclones. In the Caribbean they are called the God of All Evil, and were meant to punish those who angered the Gods. Whatever hurricanes are called, they are the greatest storms on Earth.
The birthplace of hurricanes is in the tropics. They begin between the latitudes of 5 and 20 degrees north or south of the equator, in the areas where the ocean temperatures reach 80 during summer and fall.
Hurricanes begin as an unstable air mass, often when the convergence zone created by the trade winds of the two hemispheres is displaced over unusually warm areas of sea. It must be far enough from the equator for rotational forces to cause to winds to spiral, counterclockwise in the northern hemisphere, and clockwise in the southern hemisphere.
The hurricane gets its energy supply from the ocean, drawing energy as heat is transferred from water to air. Large amounts of water vapor are evaporated and carried upwards in strong spiraling winds. Clouds increase when the latent heat is released as the vapor condenses into clouds. As warm air and moisture rise, a low pressure area is created near the surface. This pulls in more air and moisture and the system grows. This process continues until the system reaches 90 to 400 miles across.
When wind speed reaches 39 miles per hour, the storm is classified as a tropical storm and the storm system is given a name. The old tradition of giving storms feminine names was abandoned in 1979, now they receive both male and female names.
In one out of 10 tropical storms, wind speed exceeds 74 miles per hour; these storms are then upgraded to hurricane. Hurricanes can grow to 300 miles or more across, and move 10 to 50 miles per hour. Wind speeds within these storms can reach 200 miles per hour.
One of the oddest things about hurricanes is the eye of the storm. In the very center of the storm system lies an area up to 25 miles across that is remarkably calm and serene. Hurricane survivors talk of how strange it was to go out and view the eye of the storm: blue sky overhead surrounded by a wall of angry clouds. Ships at sea have been known to survive hurricanes by riding them out in the eye of the storm.
The winds of a hurricane cause a great deal of damage, but this can be minor when compared to the waves that attack coastal areas. The hurricane itself is a low pressure area, but the eye in the middle is a high pressure area. This high, together with the intense low pressure surrounding it, creates a suction around the center that literally raises a wall of water as much as 10 feet high. This wall of water is pushed ahead of the hurricane and can grow to as much as 25 feet high, and these waves are intensified by the winds. When these waves are driven into the area of a bay, the compression effect of the surrounding land mass can cause the waves to grow to as much as 40 feet. This already bad situation can be made even worse when it coincides with a high tide.
More deaths have occurred from hurricanes than from volcanoes and earthquakes. One of the worst hurricanes in recorded history occurred in 1970 hitting Bangladesh and killing 500,000 people. In our country, we’ve been more fortunate; the worst hurricane in U. S. history was a 1900 storm that killed 6000 in Galveston Texas.
Hurricanes last about ten days. Though they generally follow a westward path across the South Atlantic and then arc toward the north near our east coast, Hurricanes follow a very erratic path. A hurricane can change its path so suddenly that it is difficult to predict where it will go.
Ironically, there is a useful side to hurricanes. These tropical storm systems serve to circulate intense heat from the tropics, sometimes supplying rainfall to areas that would otherwise be dry. But it seems a small benefit when one looks at the fatality figures.
Thanks to weather satellites, we are able to track hurricanes better than ever before, and though we may not be able to predict their exact paths, we at least are forewarned.
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