document: Tetsuya Theodore Fujita saw his only natural tornado near Denver in 1982 . `` It was like meeting my lover , '' he says . `` Since then , my passion really went up , '' said Fujita , a professor of geophysical science who has been studying tornadoes for 42 years and is considered one of the world 's foremost authorities on the violent storms . Fujita , 69 , spends much of his time in his lab at the University of Chicago creating tornadoes for research . He creates tornadoes over a large fan , which makes a swirling motion ; another fan above simulates a low-pressure system by adding an updraft to the mix . With a bit of steam added to make the phenomenon visible , he creates twisters six to eight feet tall . The miniature versions are as impossible to redirect or squelch as their full-size cousins , he says . He has tried by crawling right up next to them and using rulers or books to change their direction . Fujita came to the United States from Japan in 1953 , partly because there are so many tornadoes in this country . `` Tornadoes are very rare in Japan , '' Fujita said . `` They have about 10 to 15 a year . But one occurred within about 15 miles of my hometown . I was quite impressed with the localized severity of the wind . '' When he saw his first tornado , he and a team of scientists were studying wind shear and its effect on aircraft . `` It 's a beautiful thing , '' Fujita said . `` Of course , I was 20 miles away from that one . `` If you 're in it , '' he added , `` it 's a terrible thing . '' Forecasters still have trouble predicting tornadoes . But Fujita has helped define the conditions most likely to spawn them . Groups of thunderstorms are not as likely to spawn tornadoes as single , large storms because multiple storms in the same area compete . `` Each one tries to rotate , but they all ca n't . They 're just like human beings : The rich may become richer and the poor may get poorer . '' Fujita also discovered that most strong tornadoes are actually six or seven small twisters he calls suction vortices , rotating around the center of a larger tornado . `` A suction vortex can pick up a car or a small house or something , but when you 're standing right next to it you can be completely safe . '' He has studied tornadoes that have dropped houses into lakes , made off with one car and left another right next to it untouched , and moved whole flocks of cows and sheep -- which lived through the experience . He also developed the Fujita scale for measuring the strength of tornadoes . It runs from zero -- a tornado that might break twigs on trees -- to five -- a twister that can rip houses from their foundations . But Fujita considers his work on other air movements called downbursts and microbursts among his most significant achievements . Downbursts are powerful drafts of air moving down from a thunderstorm cloud . Scientists long thought the drafts dissipated before reaching the ground . Microbursts are smaller versions of downbursts , but are more dangerous because they give pilots less time to react , Fujita said . The National Transportation Safety Board has cited microbursts , a term coined by Fujita , as the cause of 17 aircraft accidents in the last 15 years , causing 577 fatalities . Among them was the 1985 crash of a Delta L-1011 in Dallas that killed 137 people . A downburst also was implicated in the collapse of a wall at a school in Newburgh , N.Y. , that killed nine children . Fujita 's work helped persuade the Federal Aviation Administation to begin installing a new radar system at 47 major airports beginning in the early 1990s . The Doppler radar system was credited with helping three jetliners at Denver 's airport avoid potentially catastrophic microbursts last year . Fujita retires from teaching this year , but will continue his research at the university . `` In Texas one time , five people were killed when they drove right into a tornado . They just did n't know any better , '' Fujita said . `` I want to make people safer . ''
extractive_keyphrases: tornadoes natural tornado fujita violent storms thunderstorms small twisters scientists