DOPPLER DEAD ZONES MAKE TORNADOES EVEN MORE DANGEROUS

By Kenneth Heard

Called “Doppler dead zones,” there are areas in the state that are too far away from National Weather Service radars to accurately detect the formation of tornadoes and other serious storms.

One of the most populated areas in Arkansas that doesn’t receive higher resolution radar data is Cherokee Village, a town straddling Fulton and Sharp counties. Perched in the foothills of the Ozark Mountains and snug along the Spring River, the town of 4,800 is almost the same distance between Weather Service Doppler radars in North Little Rock, Memphis, Paducah, Ky., and Springfield, Mo.

Because of the distance and the earth’s curvature, radar sig- nals cannot see anything below 11,000 feet in Cherokee Village. The “hook echoes,” or the hook-like appearance on radars that are major indicators of rotation and tornadoes, are usually visible up to 7,000 or 8,000 feet, said Dennis Cavanaugh, the National Weather Service warning coordination meteorologist in North Little Rock.

Doppler radars look like large white golf balls sitting atop multi-story, metal-framed towers. They send signals into storms and record data that reflect off of rain and hail. The radars can determine wind speeds, direction of the storm’s travel, if large hail is forming, whether wind is rotating and other meteorological information.

Radar resolution has improved in recent years; Dopplers can even pick up “debris balls,” indicative of violent tornadoes damaging homes, barns, cars and trucks and other items and tossing the damage into the skies.

But receiving clear, detailed resolution is dependent upon how low the radars can reflect signals.

“We’re likely to see possible rotation high up in the towering supercells [in Cherokee Village], but not lower with a lot of confidence,” Cavanaugh said.

There is another “Doppler dead zone” along the Arkansas and Louisiana border and there are several spots across the U.S. that cannot be viewed clearly by radar. About 160 Doppler radars cover weather across the country for the National Weather Service.

Each cost in the millions of dollars, Cavanaugh said, and up to $1 million a year in maintenance and calibration of the radars.

“We’re doing the best we can with what we have,” he said.

That’s why towns like Cherokee Village rely heavily on trained weather spotters, those brave souls who venture out in inclement weather to watch for storms.

“The only things we can really see [on radar] are the supercells,” Jeremy Langston, director of the Fulton County Office of Emergency Management, said. “If it’s less than 20,000 or 30,000 feet, you have no idea. We just have to guess.”

Langston said he checks a National Oceanic and Atmospheric Administration website for the convective outlook that predicts where the more volatile storms may form. Then he looks at the websites of professional storm chasers like Reed Timmer and Brett Adair to see where they are going. If they’re headed toward north central Arkansas, Langston knows to get his storm spotters out.

He also uses information from other areas of the state that are within better Doppler coverage.

“If you see some serious storms headed your way, you know where weather is fixing to happen,” he said.

On Feb. 5, 2008, Cherokee Village was at the tail end of the longest-tracked tornado in the state’s history.

The twister began in Centerville in Yell County and roared through seven counties, staying on the ground for 122 miles before crossing into Missouri. Langston said he helped with cleanup in Highland, a town next to Cherokee Village, after that twister.

“I saw a White River [Medical Center] hospital sign on the ground,” he said. “I thought, ‘We don’t have a White River hospital near here.’”

He looked closer and saw the sign was from the medical center in Mountain View, blown by the tornado from some 50 miles away.

“Our storm spotters are very important,” Langston said. “It gets hard. We try to get mass notifications to our residents to let them know to be alert. We have an active group of spotters.”

There has been talk of private businesses like Climavison, a company based in Louisville, Ky., that installs high-resolution radars in the “dead zones” to fill existing coverage gaps. The company sells the data to the Weather Service.

Langston said he’s heard rumors that such a company could place a radar across the state line into southern Missouri. So far, though, there’s been no definite word about that.

“Our main function is to protect our citizens,” said Cherokee Village Mayor Stephen Rose. “We wish everybody could have a Doppler radar in their backyards, but that’s not going to happen.

“We don’t have the technology to stop tornadoes, but we should be able to provide earlier warnings to our residents,” he said.

Cavanaugh holds storm spotting seminars during the spring when storms become more frequent, teaching people how to identify the formation of tornadoes and how to be safe when doing so.

“Spotters have a high level of dedication to public safety,” he said. “They provide more coverage for us across the state.

“People may think that places like Cherokee Village don’t get as many storms as other areas in the state,” the warning coordinator said. “But the tornado risk is as high there as any other point in the state. Having spotters see things that our radars can’t see makes our warnings more meaningful.”