Hurricanes begin as tropical storms over the warm moist waters of the Atlantic and Pacific Oceans near the equator. Near the Phillippines and the China Sea, hurricanes are called typhoons. As the moisture evaporates it rises until enormous amounts of heated moist air are twisted high in the atmosphere. 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. If you could slice into a tropical cyclone, it would look something like this. The small red arrows show warm, moist air rising from the ocean's surface, and forming clouds in bands around the eye. The blue arrows show how cool, dry air sinks in the eye and between the bands of clouds. The large red arrows show the rotation of the rising bands of clouds.
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. As the wind passes over the ocean's surface, water evaporates turns into water vapor and rises. As it rises, the water vapor cools, and condenses back into large water droplets, forming large cumulonimbus clouds. These clouds are just the beginning.
The strongest Atlantic storm was Wilma in , with winds of miles km an hour. A supercell thunderstorm strikes in South Dakota. Among the most severe storms, supercells can bring strong winds, hail, and even tornadoes. See more extreme weather pictures. The best defense against a hurricane is an accurate forecast that gives people time to get out of the way. The National Hurricane Center issues hurricane watches for possible storms within 48 hours and hurricane warnings for expected storms within 36 hours.
Climate change may be driving more frequent, more intense extreme weather, and that includes hurricanes.
The hurricane season was one of the most active on record, with 22 major hurricanes in the Northern Hemisphere in under three months, and also saw seriously devastating Atlantic storms. While a number of factors determine a hurricane's strength and impact, warmer temperatures in certain locations play an important role. In the Atlantic, warming in the Arctic could drive future hurricane tracks farther west , making a U.
Hurricane Harvey , which dropped a record-breaking A warmer atmosphere can also furnish more water vapor for making rain, as evaporation increases and warm air holds more vapor than cold. Warming temperatures can also slow tropical cyclones , which can be a problem if their progression over land is extended, potentially increasing storm surges, rainfall, and exposure to high winds.
Potential trends make it more important than ever to be prepared for coming storms and to address the root causes of climate change , scientists say.
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