Residents of Greensburg, Kansas had about 20 minutes warning before one of these destroyed their town in 2007
The town of Udall lost 20 percent of its population when a huge tornado 
... Service issued a tornado warning about 20 minutes before the twister struck,... [DOC] [TLE] Aftermath of the Greensburg Tornado - davefreeman.tv davefreeman.tv [PAR] The May 4, 2007, Greensburg, Kansas, Tornado ...