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.

(AP)