8/13/97 - What creates a tornado?

What creates a tornado?

(Lansing State Journal, August 13, 1997)


Recently, several tornado warnings and one tornado have hit our area. What is the recipe for a tornado? The ingredients are: a big thunderstorm; winds blowing from opposite directions; and a strong updraft. Strong updrafts surge up through storm clouds causing the cloud tops to bubble up and subside. A tornado can form when the air in these updrafts begins to rotate as opposing winds cause the storm to start spinning.

This whirling mass of air and cloud is called a vortex and the spinning column of air within the vortex is called a mesocyclone. The air pressure in the center of the vortex drops as more air is sucked into it, although at the present time scientists do not know just how low the air pressure can get within the center of the vortex.

As the mesocyclones get stronger they begin to shrink and spin faster. The familiar funnel shape of a tornado develops as the air pressure in the center of the vortex drops. As more and more air gets drawn into the funnel it accelerates upwards and the funnel stretches.

Tornado Trivia: Wind speeds within a tornado may reach 600 miles per hour, and objects picked up by a tornado hurtle around it at the same speed. The United States is the tornado capital of the world with an average of 700 tornadoes per year. The U.S. has this many tornadoes because of west winds. Winds from the west are forced to stream over the Rocky Mountains. On the other side these winds encounter the low, warm, moist winds from the Gulf of Mexico. These two air masses collide over the central U.S and provide the possibility for tornado development. That's why Kansas had more than 1200 tornadoes from 1953 to 1980 while Alaska only had one.



[ Back to Ask Science Theatre | Back to Ask Science Theatre Date Index ]
Back to MSU Science Theatre Home Page