Thursday, October 10, 2013

Germantown residents to hear outdoor sirens less often

Residents of Germantown, TN will be hearing outdoor warning sirens less often, but it's not necessarily a bad thing.  A couple of weeks ago, Germantown flipped the switch on new software and an updated siren policy that allows the city to make their own decisions about warning their residents and visitors during severe weather episodes. [Media release from the city of Germantown]

Background and warning policy

Using a $77,000 grant from the Department of Homeland Security, Germantown installed a complete weather system from Earth Networks (the company that owns WeatherBug) that includes a professional weather station, an HD camera, and Streamer RT software.  The weather station, located on top of fire station #3 adjacent to the Germantown Municipal Center, and HD camera, mounted on top of the city's tallest water tower, provide realtime local conditions and a great view of the sky to Germantown officials and anyone else who visits the WeatherBug website or mobile app. However it is Streamer RT that allowed Germantown to modify their tornado warning policy.

The city of Germantown and it's 17.6 square miles and 38,000+ residents are well-covered by 15 outdoor warning sirens with overlapping coverage. (On average, each siren has an audible range of just over a 1 mile radius, or 3.5 square miles.)  Until recently, Germantown followed the siren policy used by the rest of Shelby County and it's municipalities, which required that all sirens county-wide be sounded when any part of the county was affected by a Tornado Warning.

Now, using the graphical overlays available in the software, city dispatchers (whose duties include activating the city's sirens) will look at the display that depicts the Germantown city limits and the warning polygon issued by the National Weather Service (example below) and determine whether to activate the sirens. If the warning polygon does NOT include a portion of the city, sirens will not be sounded.  If any part of the city IS in the warning, sirens will be sounded. And once the warning is lifted for all of Germantown (even if it still encompasses other parts of Shelby County), sirens can be shut off.

Streamer RT software by Earth Networks provides Germantown dispatch and fire with current weather info, as well as warning polygons and the city limits, making the decision to warn the city, or not, an easy one.  In this case, sirens would not be activated. Image courtesy Germantown FD.

Fewer sirens = more trust in the system

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 expected to be impacted by these events, irrespective of political boundaries (such as the red polygon in the image above).  However, many warning systems, including the NWS' own 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 in the warned area.  Besides weather radio, some commercial radio and TV stations still warn based on counties (though most are moving away from county-based warning), and in most places sirens still warn entire counties, including in Shelby County.  Because the cities of Germantown, Bartlett, and Collierville (as well as Memphis) activate their own sirens, they are able to break away from county-based siren activation simply by changing their internal policies.  Germantown is the first to do so.  Bottom line: going forward, when sirens sound in Germantown, residents can be certain that all or some part of their city is under a direct threat.

The process to transition to this policy actually began two years ago with a search by Germantown Fire officials for companies that would provide the tools to allow them to sound their own sirens.  When asked why Germantown decided to change their siren policy, Chief John Selberg summed it up this way: "I believe in being prepared without over-sensationalizing the emergency."  Ultimately, he expects the change in philosophy to "reduce complacency" since the sirens will only sound for actual threats to the city.


Of course, we can't have a discussion of outdoor warning sirens without discussing the caveats.

First and foremost, never rely on sirens when indoors! It's very important to remember that outdoor warning sirens are called that for a reason - they are intended to alert people who are OUTDOORS to go inside and seek additional information on the threat.  Though Germantown's sirens have excellent coverage, if you are asleep with the air conditioner running and it is raining outside, it is doubtful that you will hear the sirens and you place yourself at risk.

Have a programmed NOAA Weather Radio with good batteries and, if you have a smartphone, install a severe weather app that will alert you (and wake you) in case of severe weather.  It should have a feature that will wake you for the most intense storms, allow you to program multiple locations, and preferably have a "follow me" feature for when you are traveling. We highly recommend our MWN app with StormWatch+, which fits the bill perfectly.

One of these methods in and of itself is not sufficient.  Always have multiple ways of receiving severe weather information.  Any one of them can fail at any time and you need a backup or two.

NOTE: Germantown sirens are tested on Saturdays at noon (unless the weather is threatening) and the sirens are all equipped with two-way communication which means the Germantown Fire Department knows, without activating the sirens or being on-site during a test, when a siren is not working properly.

Additional links/info:
Outdoor Warning Sirens page on
Germantown Fire Department page on City of Germantown website
Germantown Fire Department on Facebook
"Weather system to limit siren sounds in Germantown" - Commercial Appeal

Outdoor warning sirens series on the MWN Blog:
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Visit on the web or on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!

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