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| A new siren next to the water tower at Rivercrest Elementary School |
As with Germantown and Collierville, Bartlett officials will only sound their outdoor sirens when a Tornado Warning (issued by the National Weather Service) intersects or overlays the Bartlett corporate limits, rather than anytime any portion of Shelby County is warned. Bartlett operates twelve (12) sirens with an effective radius of about 1 mile (or 3.5 square miles coverage) to warn their 58,000+ residents in the city limits. (Read the Press Release describing the change.)
In addition, the updated siren policy states that sirens will be sounded for 3 minutes, followed by a 2 minute pause, with the cycle repeated until the Tornado Warning is no longer in effect. This cycle will prevent the siren's mechanical parts from "burning up" that sometimes occurs when they have been running for tens of minutes with no break.
Background on polygon warnings
In 2007, the National Weather Service ceased warning entire counties for tornadoes, severe thunderstorms, and flash floods. Instead, these warnings are now issued on a storm basis. As we've described before, a polygon is drawn around the area in the path of these events, irrespective of county or state boundaries. However, many warning systems including NOAA Weather Radio still send alerts on a county-wide basis, resulting in larger areas being warned than the NWS intended via their polygon system. County-wide alerting result in "perceived overwarning" because people using those warning systems perceive a threat, when oftentimes they are not actually in the warned area. In the cases of Germantown and Bartlett, software designed by Earth Networks will show the polygon warning and the city limits and make the decision whether or not to sound the sirens straight-forward. |
| A Tornado Warning polygon issued for parts of Shelby County on January 23, 2012, is an example of one that would NOT require the sounding of Bartlett sirens, as the polygon does not touch the city limits. All other sirens in Shelby County would sound if this warning were issued again. |
Caveats of outdoor warning sirens
We cannot have a discussion of sirens though without talking about the main drawback of sirens. They are called OUTDOOR warning sirens for a reason! Sirens are to alert people outdoors that may be away from a news or weather source that dangerous weather is nearby and to seek additional information. They are not designed to wake you up in the middle of the night or be heard in a well-insulated structure over television, air conditioners, heavy rain or wind.
When indoors or asleep, ALWAYS have other sources of severe weather alerts that will grab your attention, such as our MWN mobile apps with StormWatch+ precision weather alert technology or a NOAA Weather Radio. In fact, everyone should have MULTIPLE ways of receiving life-saving severe weather bulletins, as any one can fail at any time.
Bottom line for those in Bartlett and Germantown - if sirens are sounding, you can expect that it is because your towns are within the tornado warned area and you should seek shelter immediately! (Sirens in both communities are tested on Saturdays at noon, weather-dependent.)
Additional links/info:
Outdoor Warning Sirens page on MemphisWeather.net
Bartlett Fire Department page on City of Bartlett website
Bartlett Fire Department on Facebook
Outdoor warning sirens series on the MWN Blog:
- Part 1 (Role of the EMA)
- Part 2 (Role of warning sirens)
- Part 3 (The warning process & the future of warning systems)
Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!
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