Shop Windows to the Universe

Learn about planets outside our solar system through Exoplanets and Alien Solar Systems by Tahir Yaqoob, Ph.D., a book in our online store book collection.
Five things that a hurricane needs
Click on image for full size
Lisa Gardiner/Windows to the Universe

How Hurricanes Form

A thunderstorm in the tropics can grow into a massive hurricane under certain conditions. Sometimes several tropical thunderstorms are able to organize, rotating around a central area of low pressure. This is called a tropical depression. If the depression strengthens so that winds reach at least 39 mph, it is called a tropical storm. And if wind speeds increase to more than 74 mph, it is called a tropical cyclone or hurricane.

A study found that out of 608 possible storms only 50 developed into tropical storms. A storm will strengthen if there is a supply of warm, moist air to feed it. Warm, moist air is found above warm, tropical ocean waters.

Once they form, hurricanes take energy from the warm ocean water to become stronger. While a hurricane is over warm water it will continue to grow. A hurricane dies when it moves away from the tropics. When a hurricane moves into higher latitudes where there is cooler ocean water, it looses its power. There is no longer a supply of warm, moist air near the ocean surface to feed the storm so it shrinks. It will also weaken if it travels over land.

The rotation of the storm is due to the Coriolis Effect, a product of the Earth's rotation. This causes the air being drawn into the central low pressure to curve. The incoming air must go somewhere so it rises as it rotates. This rising air, which is saturated with water, cools and condenses, forming clouds. Hurricanes do not occur within 300 miles (500 kilometers) of the equator because there is no Coriolis Effect at the equator.

Last modified March 13, 2009 by Lisa Gardiner.

Shop Windows to the Universe Science Store!

The Fall 2009 issue of The Earth Scientist, which includes articles on student research into building design for earthquakes and a classroom lab on the composition of the Earth’s ancient atmosphere, is available in our online store.

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Science, Evolution, and Creationism

How did life evolve on Earth? The answer to this question can help us understand our past and prepare for our future. Although evolution provides credible and reliable answers, polls show that many people turn away from science, seeking other explanations with which they are more comfortable....more

Low Pressure Systems

You may have seen a weather map with a red L on it. This red L denotes a low pressure system in that area of the map. Just what does that mean? The H for high pressure systems and alternatively the L for...more

Earth's Ocean

Earth's ocean covers more than 70% of our planet's surface. There are five major ocean basins. The Pacific Ocean is the largest. It’s so large that it covers a third of the Earth's surface. The Atlantic...more

Hurricane Damage

Rain, wind, tornadoes, and storm surge related to hurricanes cause change to natural environments, damage to the human-built environment, and even loss of life. When a hurricane is over the ocean and far...more

Scientists Study Hurricanes of the Future

Researchers are homing in on the hurricane-prone Gulf of Mexico and Caribbean Sea to assess the likely changes, between now and the middle of the century, in the frequency, intensity, and tracks of these...more

Are Hurricanes Becoming Stronger and More Frequent?

In 2004, a record number of hurricanes affected Florida and typhoons struck Japan. A hurricane even formed in a very unusual place, in the South Atlantic Ocean, off the coast of Brazil in 2004. No one...more

The 2005 Hurricane Season Is Churning the Atlantic

The hurricane season in the North Atlantic is particularly strong this year. And scientists predict that the storms will be getting stronger because of global warming. Follow the links below to find out...more

Why the Different Airplanes?

Why do the 53rd Weather Reconnaissance Squadron and the Hurricane Research Division use different airplanes? Actually, they only use two main types. The top two airplanes in the graphic, the WC-130H Hercules...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA