Radar detection may fail to spot smaller tornadoes

Published 23 February 2010

Even though meteorologists use multiple radar stations to monitor thunderstorms, small tornadoes can escape the detection of radar scans. Smaller tornadoes do not level entire towns like their bigger brethren, which can be more than a half-mile wide, but the small twisters can cause widespread damage

On the plains of Midwestern states, tornadoes can be spotted from a long way off. In the Tennessee Valley, where rolling terrain, trees and rain can obscure tornadoes, residents often do not see the storm until it’s almost on top of them. Sometimes the warning sirens do not begin to blow until the tornado is on the ground because it formed and touched down in less than five minutes.

Times Daily’s Dennis Sherer writes that Dave Nadler, warning coordination meteorologist at the National Weather Service office in Huntsville, said detecting tornadoes in the Southeast is challenging. While massive tornadoes are easier to detect, small, short-lived tornadoes continue to test meteorologists. “It takes four to five minutes from the time the radar beam scans a location until it comes back around and scans that location again,” Nadler said. “We can have one of the smaller EF-0, EF-1 tornadoes spin up and touch down within that amount of time. Tornadoes in the Tennessee Valley can form, come down and dissipate within five to seven minutes.”

Sherer writes that tornadoes are rated by the Enhanced Fujita system, which measures their intensity on a scale of 0 to 5. Top wind speed in an EF-0 tornado is 85 mph. Winds in an EF-5 tornado are more than 200 mph.

Even though meteorologists use multiple radar stations to monitor thunderstorms, small tornadoes can escape the detection of radar scans. Smaller tornadoes do not level entire towns like their EF-4 and EF-5 counterparts that can be more than a half-mile wide, but the small twisters can cause widespread damage.

Mike Melton, director of the Colbert County Emergency Management Agency Whenever said that if there is a threat of severe storms, residents should pay attention to weather conditions and be ready to seek shelter if they believe a tornado is on the way, even if no warning has been issued, said. “You need to start making preparations for seeking shelter when a tornado watch is issued,” Melton told Sherer. “You need to begin thinking then about where you would go during a tornado. It’s too late to begin thinking about what to do when the warning is issued and the tornado is already on the ground and coming right for you. Sometimes, you are not going to even get a warning, so you need to have a plan and know what you are going to do anytime there is just the potential for tornadoes.”