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.
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
You might also be interested in:
What types of instructional experiences help K-8 students learn science with understanding? What do science educators teachers, teacher leaders, science specialists, professional development staff, curriculum designers, school administrators need to know to create and support such experiences?...more
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 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
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
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
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 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 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