US

Precise combination of factors create Okla. killer tornado with power of many Hiroshima bombs

  • An aerial view of a street lined by homes destroyed by Monday's tornado is shown Tuesday, May 21, 2013, in Moore, Okla. At least 24 people, including nine children, were killed in the massive tornado that flattened homes and a school in Moore, on Monday afternoon. (AP Photo/Tony Gutierrez)

    An aerial view of a street lined by homes destroyed by Monday's tornado is shown Tuesday, May 21, 2013, in Moore, Okla. At least 24 people, including nine children, were killed in the massive tornado that flattened homes and a school in Moore, on Monday afternoon. (AP Photo/Tony Gutierrez)  (The Associated Press)

  • A demolished home with the car flipped over is all that remains left behind in the damage from the tornado that hit the area near 149th and Drexel on Monday, May 20, 2013 in Oklahoma City, Okla. (AP Photo/ The Oklahoman, Chris Landsberger)

    A demolished home with the car flipped over is all that remains left behind in the damage from the tornado that hit the area near 149th and Drexel on Monday, May 20, 2013 in Oklahoma City, Okla. (AP Photo/ The Oklahoman, Chris Landsberger)  (The Associated Press)

  • A local resident allowed by security officers into an otherwise sealed off neighborhood walks past the rubble of destroyed homes, one day after a tornado moved through Moore, Okla., Tuesday, May 21, 2013. The huge tornado roared through the Oklahoma City suburb Monday, flattening entire neighborhoods and destroying an elementary school with a direct blow as children and teachers huddled against winds up to 200 mph. (AP Photo/Brennan Linsley)

    A local resident allowed by security officers into an otherwise sealed off neighborhood walks past the rubble of destroyed homes, one day after a tornado moved through Moore, Okla., Tuesday, May 21, 2013. The huge tornado roared through the Oklahoma City suburb Monday, flattening entire neighborhoods and destroying an elementary school with a direct blow as children and teachers huddled against winds up to 200 mph. (AP Photo/Brennan Linsley)  (The Associated Press)

Wind, humidity and rainfall combined precisely to create the massive killer tornado in Moore, Okla. And when they did, the awesome amount of energy released over that city dwarfed the power of the atomic bomb that leveled Hiroshima.

Meteorologists contacted by The Associated Press used real time measurements to calculate the energy released during the storm's life span of almost an hour. Their estimates ranged from 8 times to more than 600 times the power of the Hiroshima bomb.

Scientists know the key ingredients that go into a devastating tornado. But they are struggling to figure out why they develop in some big storms and not others. They also are still trying to determine what effects, if any, global warming has on tornadoes.