Tornado disaster: Why so deadly?

On Sunday, May 22, the deadliest single tornado in U.S. history devastated Joplin, Mo., killing 159.

Both the government's Storm Prediction Center, in Norman, Okla., and the local Springfield, Mo., National Weather Service office provided plenty of warning.

However, it appears that most people in the area didn't respond to the first siren warnings that day, according to a post-storm report released today by the National Oceanic and Atmospheric Administration.

Whether that contributed to an increase in the death toll is uncertain, NOAA said, but it was clear from the survey of residents that the initial sirens weren't viewed as a general call to action.

NOAA said that a variety of reasons contributed to that lack of response. To quote from the report:

"The perceived frequency of siren activation in Joplin led the majority of survey participants to become desensitized or complacent to this method of warning.

"This suggests that initial siren activations in Joplin (and severe weather warnings in general) have lost a degree of credibility for most residents."

One element not addressed in the report is the fact that the outbreak occurred late on a Sunday afternoon when some people might have been paying full attention to the weather. Could that have contributed to the death toll?

"It's hard to pin that down," Dick Wagenmaker, leader of the NOAA assessment team and meteorologist in charge of the Detroit-area weather service office, said later in a phone interview.

Wagenmaker noted that on a day that 4,000 students graduated from the Joplin high school that day. The school was destroyed; fortunately, the graduation ceremony was held elsewhere.

Incidentally, if you click on the report, on Page 25 you'll find radar images of a "debris ball," literally a swirling mass of debris hurled skyward by one of the most-destructive and powerful storms ever detected on planet Earth.