It was a warm, damp day in central Nebraska, heavy and still. The tornado arrived at the Madsen farm just before 3 p.m. Mads Madsen, 63, his wife Minnie, 59, three of their children and five of their grandchildren were in the parlor eating Sunday dinner. Twenty minutes later all 10 of them were dead.

“There was a roar like hundreds of airplanes, then an explosion,” Joy Lutz recalled years later. She was crouching in a cave with her husband, Guy, and their three children at the next farm up the road. Then came a second explosion, “louder and longer than the first,” she wrote. Then quiet. Mr. Lutz went outside to reconnoiter. Their own house was flattened. The Madsen place had virtually disappeared.

That tornado, in Arcadia, Neb., on June 7, helped for six decades to make 1953 the deadliest year for tornadoes since the National Weather Service and its predecessor, the Weather Bureau, began keeping records. That record of 519 fatalities has been eclipsed, with more than 520 recorded so far this year. Neither year, however, has had anything remotely approaching the 1925 Tri-State tornado, the deadliest single tornado in United States history, which killed 695 people by unofficial count.

Tornado forecasting and the technology that accompanies it have improved greatly over the years, researchers say. Thanks to heightened reporting and awareness, better building practices and inventions like the radio and Doppler radar, tornado fatalities have declined steadily for nearly a century.

But the disasters of 2011 underline a lingering reality: Many of the circumstances that were beyond science in 1953 are still beyond science today....