Saturday, May 14

A mass of cold, dry air that was born in the Gulf of Alaska travels down the West Coast to California. It moves east, crossing the Rocky Mountains. In eastern Colorado, it collides with a stream of warm, moist air that blew up from the Gulf of Mexico. A violent storm system is born.

Sunday, May 15

The system unleashes a powerful thunderstorm across Colorado. Small tornadoes touch down east of Denver.

Saturday, May 21

The system gains strength as it marches east into Kansas. At 9:15 P.M., a tornado touches down in the tiny town of Reading, population 231. It severely damages the downtown. A fifty-three-year-old man is killed.

Sunday, May 22

The day dawns bright and clear in Joplin, Missouri. There are forecasts for thunderstorms for later in the afternoon.

1:30 P.M.: The National Weather Service issues a tornado watch for Joplin and surrounding areas. A tornado watch means that the conditions are right for tornadoes, but that there is no specific threat.

2:00 P.M.: The storm system moves into eastern Kansas. Fifty miles northwest of Joplin, it forms a violent supercell, which unleashes rain and hail over the town of Parsons.

4:30 P.M.: There is so much energy in the air that two more supercells develop to the south of the main storm. In Columbus, Kansas, twenty-five miles northwest of Joplin, rain and baseball-size hail fall from the sky. The three supercells begin to move east, toward Joplin.

5:00 P.M.: The National Weather Service issues a tornado warning for areas in Missouri, Kansas, and Oklahoma. A tornado warning is more severe than a tornado watch. It means that a threat is imminent — that a tornado is almost certainly coming — and that people should take shelter. But this warning covers only the northeastern portion of Joplin, and weather forecasts suggest that the worst of the storm will hit north of the city.

5:11 P.M.: Joplin’s twenty-eight tornado sirens wail. They sound for three minutes and then go silent. No tornadoes touch down.

5:17 P.M.: A new tornado warning is issued that includes all of Joplin.

5:20 P.M.: Four young storm chasers, driving on a road four miles west of Joplin, witness the moment when wisps of clouds transform into a black churning tornado. Within minutes, the tornado is wrapped in a curtain of rain. It is completely invisible as it heads into Joplin.

5:30 P.M.: Another team of storm chasers, Jeff and Kathryn Piotrowski, is following a storm into Joplin. The two are among the first to realize that the gray cloud to the west is a massive rain-wrapped tornado. Jeff stops to alert a Joplin policeman, who is sitting in a parked car. “Get the sirens going,” Piotrowski warns.

5:31 P.M.: Joplin’s sirens sound a second time.

5:32 P.M.: The tornado, now three-fourths of a mile wide, begins its attack on Joplin.

5:43 P.M.: Weather forecasters stare in shock at their radar screens; the area above southern Joplin is filled with pink splotches, indicating debris from the city that a tornado has thrown thousands of feet into the sky.

The tornado grinds on for thirteen more miles, laying waste to a third of Joplin.

6:12 P.M.: The tornado disappears into the sky.