WASHINGTON - New radars installed by the National Weather Service in the 1990s are saving nearly 80 lives a year that would otherwise be lost to tornadoes, a study concludes.
The radars allowed forecasters to issue warnings for 60 percent of tornadoes, up from 35 percent before the instruments were installed, and the average lead time rose from 5.3 minutes to 9.5 minutes, according to a study published in the June issue of the journal Weather and Forecasting.
Kevin M. Simmons of Austin College in Sherman, Texas, and Daniel Sutter of the University of Oklahoma studied 14,979 tornadoes that struck in the United States between 1986 and 1999. Of those 7,900 occurred before the new radars were installed and 7,079 took place afterward.
They rated the twisters by size, distance traveled, population density where they struck and other factors and compared the damage done before and after the modern radars were installed.
Their conclusion: 79 fatalities and 1,050 injuries per year have been avoided because of the Doppler radars.
Elbert W. "Joe" Friday, who headed the National Weather Service during the years the new equipment was being installed, said the finding "really does validate the modernization."
The lifesaving makes all the effort worthwhile, Friday said in a telephone interview. Now retired from the Weather Service, he was not part of the research team for this study.
Simmons, who did extensive wind damage studies at Texas Tech before moving to Austin College, said the analysis was done at the request of the National Severe Storms Laboratory in Norman, Okla., a branch of the National Weather Service that studies severs weather such as tornadoes.
Simmons and Sutter said they did not try to determine exactly how the new radars saved lives, but they noted that the percentage of tornadoes detected increased as did the amount of warning time before twisters struck.
For all tornadoes, the percentage of tornadoes for which warnings were issued jumped from 35 percent to 59.7 percent, they said.
For the most powerful Category 5 storms the warning rate went from 80 percent to 100 percent and for the also deadly Category 4 twisters the warning rate went from 64.2 percent to 93.5 percent.
For all tornadoes, the amount of warning time went from 5.3 minutes to 9.5 minutes. But for the Category 5 storms it jumped from 11.7 minutes to 16.23 minutes and in Category 4 the warning time grew from 8.6 minutes to 15.0 minutes.
Detecting a larger share of twisters earlier provides more time to warn local media and emergency managers and for people to hear them and get to a safer location.
Doppler radar can detect not just the presence of rain or hail, like conventional radar, but can measure which direction it is going and how fast. The storm clouds that produce tornadoes are filled with rain, hail and often debris, that these radars can detect and measure.
Weather and Forecasting is published by the American Meteorological Society.