Although hurricanes have high wind speeds, they are born in areas with light winds. Heavy winds at the start will often cause wind sheer, stopping the process before the storm can reach hurricane force. Wind speeds gradually increase as the storm grows in size, until they potentially reach speeds of 200 mph or more. Hurricane Katrina's winds were 127 mph when it struck land. Knowing the storm's wind speed makes it easier to prepare for landfall.
Hurricanes rotate counter-clockwise around their eye. Calculating wind direction helps to predict when the storm will reach hurricane force and where it will hit land. To obtain the data, special aircraft are deployed to the storm area. They hover 500 to 1,000 feet in the air above the storm, then drop a series of dropsondes. A dropsonde is an electronic instrument that measures wind speed and direction and transmits it back to the aircraft.
According to the National Aeronautics and Space Administration (NASA), hurricanes can sometimes be predicted by a quick drop in barometric pressure. When the area becomes a low-pressure region, a hurricane may hatch. Air moves out of neighboring high-pressure areas, and the Earth's rotation causes the winds to spin in a counter-clockwise direction. Paying attention to the pressure systems around potential storms is a useful way to predict when and where they can occur.
Hurricane's require a very high humidity to form, along with warm water. The surface temperature of the water has to be at least 80 degrees Fahrenheit, which leads to quick evaporation. Rapidly rising hot air inside the hurricane creates areas known as "hot towers," which lift the water vapor up and pour them into the high winds. The massive amount of rain that comes with a hurricane can cause flooding and water damage miles inland, even in places where storm surge cannot reach.
