Hurricane how does it work

National Hurricane Center. Recipe for a Hurricane Whipping up a hurricane calls for a number of ingredients readily available in tropical areas: A pre-existing weather disturbance : A hurricane often starts out as a tropical wave.

Warm water : Water at least Thunderstorm activity : Thunderstorms turn ocean heat into hurricane fuel. Low wind shear : A large difference in wind speed and direction around or near the storm can weaken it.

Actually, the term hurricane is used only for the large storms that form over the Atlantic Ocean or eastern Pacific Ocean. The generic, scientific term for these storms, wherever they occur, is tropical cyclone. Other names they are given, depending on where in the world they are born, are typhoons, cyclones, severe tropical cyclones, or severe cyclonic storms. Whatever they are called, the same forces and conditions are at work in forming these giant storms, any of which can cause damage or devastation when they hit land where people live.

Tropical cyclones are like engines that require warm, moist air as fuel. So the first ingredient needed for a tropical cyclone is warm ocean water. That is why tropical cyclones form only in tropical regions where the ocean is at least 80 degrees F for at least the top 50 meters about feet below the surface.

The second ingredient for a tropical cyclone is wind. In the case of hurricanes that form in the Atlantic Ocean, the wind blowing westward across the Atlantic from Africa provides the necessary ingredient. It starts as a tropical disturbance.

Then, with cyclonic circulation and faster wind speeds, it becomes a tropical depression. If the wind keeps getting faster, it becomes a tropical storm and then a hurricane if winds are more than 74 miles per hour mph. The classifications are based on the wind speeds in the storm, not the size of the storm. Hurricanes that look small on radar can have very high wind speeds.

And large storms can have low wind speeds. Wind speeds in hurricanes are often measured in knots. Compared to a mile per hour, knots are a little bit faster. Then that "new" air becomes warm and moist and rises, too.

As the warm air continues to rise, the surrounding air swirls in to take its place. As the warmed, moist air rises and cools off, the water in the air forms clouds. The whole system of clouds and wind spins and grows, fed by the ocean's heat and water evaporating from the surface. Storms that form north of the equator spin counterclockwise. Storms south of the equator spin clockwise.

This difference is because of Earth's rotation on its axis. As the storm system rotates faster and faster, an eye forms in the center. It is very calm and clear in the eye, with very low air pressure. Higher pressure air from above flows down into the eye.