After a relatively mild and dry year, the Tennessee Valley has faced two severe weather threats over the past three weeks.

Tornado warnings were issued for Limestone County on Nov. 29, which led to an activation of the Tennessee Valley Authority’s outdoor warning sirens. Despite a severe weather threat last Sunday, no tornado warnings were issued.

November and December are regarded as Alabama’s secondary severe weather season. According to the National Weather Service, 247 tornadoes were reported in November from 1950 to 2015, while 132 were reported in December.

While no one wants to hear sirens in a season known more for the sound of sleigh bells, it is often a fact of life in Alabama. A damaging tornado hit the Birmingham area last year, and an EF2 tornado damaged Mobile in 2012.

To that end, TVA has been working to inspect, modify and repair 104 outdoor warning sirens located within 10 miles of Browns Ferry Nuclear Plant. Specifically, crews have been replacing bearings in sirens that may be limiting effectiveness.

During the Nov. 29 severe weather event, some Limestone County residents reported outdoor warning sirens were not working. Officials with TVA and the Limestone County Emergency Management Agency said sirens are working, but bad bearings may have prevented some sirens from rotating properly, thus impacting the broadcast of sound.

TVA Spokesman Scott Fiedler said the combination of heat and humidity can damage the bearings. Crews are down to about 20 sirens left to repair in the area and should be done later this month or by early January.

Fiedler explained a crew can repair three to four sirens per day, depending on the distance between sirens and the extent of the repair. Crews also carry a few rebuilt sirens with them in case a full replacement is needed.

He didn’t have information on the cost of the project but said, “Safety takes priority over cost.”

Siren tests

Sirens are tested the second Monday of every month to ensure operability. A silent test is also conducted every two weeks via radio link. A return signal from the siren goes to an electronic feedback system used to monitor performance. The signal is analyzed for effectiveness and Fiedler said issues are immediately corrected.

Know your calendar

TVA recently mailed 44,550 calendars to residents living within a 10-mile radius of Browns Ferry Nuclear Plant. Fiedler stressed the calendars provide safety information related to the plant and emergency procedures.

He explained the new calendars no longer have a glossy varnish and are easier to write on, as opposed to previous calendars.

“We would like everyone to take the new year to review the information and become familiar with the content,” Fiedler said.