They are called tornado chasers or storm chasers.

VOA: special.2010.05.11

Across the south and central Plains, storm chasers broadcast images of funnel clouds roaring through rural landscapes.

CNN: April 16, 2012 -- Updated 0326 GMT (1126 HKT)

"Professional storm chasers I don't have a problem with, " said Sheriff Glen Kochanowski of Saline County, Kan.

WSJ: Extreme Weather Storm Chasers Create Chaos for Emergency Crews

Meanwhile, residents in Oklahoma cleaned up after the storms there killed 13 people, including three veteran storm chasers.

WSJ: Worst storms over in East, South but more coming