Wednesday, September 23, 2009

A Tropical Storm Needs The Right Conditions

By Ken Morris

Hurricanes are among the most destructive forces on earth. Thanks to Hurricane Katrina, we've all seen the damage they can cause. Do you know how hurricanes come about and why they occur so often in the tropics?

The earth, as we all know, rotates around the sun and its axis is tilted toward the sun. These factors are major elements of tropical weather. The tropics gather a lot of heat, which must be dissipated. A tropical storm is how this heat is dissipated to surrounding latitudes.

Hurricanes, typhoons and tropical cyclones are the most powerful tropical storms. (They are called hurricanes east of the International Date Line, typhoons west of that line and tropical cyclones in the Indian Ocean and around Australia. They form when large cloud areas form into thunderstorms by convection and evaporation. If these storms are about 10 degrees or more from the equator, they can be deflected by the Coriolis Effect caused by the earth's rotation. This deflection causes the storm to rotate, increasing its power. As the storm moves away from the equator, it continues spinning faster and winds increase. If wind speed reaches 39 mph, it is classified as a tropical storm. If it reaches 74 mph, it is a hurricane, typhoon or tropical cyclone, depending on the location as listed above.

Because of the spinning nature of a tropical storm, the center of the storm, called the eye, has very low pressure. Thus conditions there are calm, the temperature is colder and the sky is clear. However, the strongest winds and heaviest rain are found at the eye wall, the area immediately surrounding the eye. Thus the eye wall can cause the most damage to property.

Because the eye wall is so powerful, meteorologists study them carefully. Stronger storms may have eye walls that form a complete circle, while weaker ones only have partially formed walls. Occasionally, the outer rings of the storm will block moisture from reaching the wall, thus weakening its momentum. As this happens, the storm may weaken but a new eye and eye wall may emerge further out from the center. When this happens the storm gets stronger causing more severe weather.

The movement of tropical storms is hard to predict, which is my meteorologists track them so closely. While they can track when high winds will arrive at an area, they cannot always predict when a storm will reach land. Storms weaken as they travel over land.

Tropical storms are most likely to occur when the surface of the ocean reaches 80 degrees F. At the time of year when this happens, it is best to be sure you have emergency plans made. Tropical storms are unpredictable and you never know when you and your loved ones will need to take cover.

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