Tornadoes!
By Sally Bryan
Original Author: Gail Gibbons
-
Cumulonimbus Clouds
3 -
Thunderhead
4 -
Updrafts and Downdrafts
5 -
Links to Additional Information
8
Tornadoes begin inside storm clouds called cumulonimbus (KYOOM-yoo-low-NIM-bus) clouds, which are made up of warm, moist air. These large, dark clouds can grow to be tall and enormous. There is lightning, thunder, rain, hail, and high winds.
When warm, humid air rises from the ground toward a dark cumulonimbus thunderhead, it creates an updraft that pulls more warm, humid air with it. When the air rises to where the temperature is cooler, condensation occurs, creating rain or hail. The cool air falls back toward Earth creating a downdraft.
If the updraft and the downdraft come together and start to spin, a funnel-shaped cloud forms inside the thunderhead and sometimes tilts into a funnel that reaches down toward the ground.
As the funnel cloud spins faster and faster, it sucks up more and more warm air and becomes bigger and louder and more powerful. If it touches the ground, a tornado is born.
In 1971, T. Theodore Fujita developed the Fujita Tornado Scale, rating tornadoes on a scale from F0 to F5. Since then the scale has been enhanced, setting stricter standards for measuring damage. Starting February 1, 2007, the Enhanced Fujita Tornado Scale has been used to classify tornadoes from EF0 - EF5.
Classifications are mostly based on the amount and type of damage caused. There is no way yet to directly measure the winds in every tornado. Wind speeds are estimates only and are based on the severity of the damage. No matter how big or little a tornado is or how long it lasts on the ground, it is likely to cause damage.
To learn more about tornadoes, visit weatherwizkids.com or watch Sullivan and Alexa build a model tornado so they could discover how these violent storms form.