Tornado Deaths on Decline
This funnel cloud developed in Clayton, N.M., well outside of "Tornado Alley."
Credit: NOAA; Doug Berry and the Ball State University Storm Chasing Team

The number of tornado deaths has decreased by nearly half since a network of Doppler weather radars were installed nationwide a decade ago, according to a new study.

The radar array has improved forecasts and warning times.

The Weather Surveillance Radar-1988 Doppler (WSR-88D), also known as NEXRAD, was installed in the 1990s during the National Weather Service's $4.5 billion modernization.

The percentage of tornadoes warned for almost doubled - from 35 percent before NEXRAD to 60 percent since. In addition, the average lead time of warnings increased more than four minutes, from 5.3 to 9.5 minutes.

The researchers, Kevin Simmons from the Department of Economics and Business at Austin College in Sherman, Texas, and Daniel Sutter from the Department of Economics and Cooperative Institute for Mesoscale Meteorological Studies at the University of Oklahoma in Norman, Okla., analyzed a dataset of tornadoes that occurred in the contiguous United States between 1986 and 1999. The date WSR-88D radars were installed at each National Weather Service Forecast Office was used to divide the sample for comparison.

The study is published in the June issue of Weather and Forecasting, a journal of the American Meteorological Society.

"Anytime public money is used to invest in a technology like Doppler radar, it is important that we evaluate the results," Simmons said. "Our study provides strong evidence that this investment has had a significant effect on reducing injuries and fatalities from these storms."

The weather service issues nearly 3,000 tornado warnings each year. About 55 U.S. residents are killed by tornadoes in an average year, but that number is declining. Last year, only 35 deaths were attributed to twisters.