Wednesday, May 25, 2011

More on Selective Tornado Siren Activation

Here an article I'd like you to read. The money quote:

Nick Crossley, director of emergency management and homeland security for Johnson County, said the warnings on Saturday night were necessary throughout the entire county.
“We erred on the side of caution,” Crossley said. “It’s much better to sound the sirens and warn people than not to sound the sirens.”

A personal note: I've met Nick and he is a dedicated public servant who wants to do the right thing. But, in this case, was sounding the sirens the right thing?

Here is the radar with the National Weather Service's tornado warning plotted in red. You'll notice only a small part (southwest) of Johnson Co. was in the tornado warning.

Sounding the sirens in Edgerton, Gardner, and Spring Hill was appropriate. I'd also say to sound them in Olathe because they are right on the edge of the warning. But the rest of the county?  No. It was a false alarm -- the tornado dissipated before it reached Johnson Co.

Earlier in the evening, the sirens went off in Lawrence even thought it was never in a tornado warning (see below):

I'm sure that emergency manager thought he or she was doing the right thing and erring on the side of safety, as well.

Here's the problem: We are training people to ignore the sirens because of all of these false activations.

The National Weather Service builds a "margin of safety" into the (relatively new, since 2005) "path-based" warnings. The emergency manager (who is not a meteorologist) building an additional margin of safety over and above the NWS's leads to far too many siren activations.

When the sirens were pressed into tornado warning service in the 1950's and 60's, the "countywide" and "err on the side of safety" philosophy made sense because meteorology was not very good at tornado warnings.

Now, meteorologists can actually predict the path of tornadoes. I believe it is time for selective siren activation to become the norm.


  1. Here's the problem with selective activation:

    Turning on all the sirens in Johnson County at once is simple. If any part of the county is in a warning, you push the button and it's done.

    Doing selective siren activation requires a map of the locations of the sirens and their coverage areas (I live a half mile into Wyandotte Co. and clearly heard their sirens. I knew it wasn't our siren, which is a block from my house and LOUD.) and either software or a human operator making the decision on which sirens are in the affected area and which are not. JoCo has 177 sirens. The complexity of managing those individually is just too great, so they divide the county into five zones, and give Gardner, Lenexa, Olathe, and Overland Park the ability to turn on their own sirens in addition to the County's own criteria.

    If you're the government official at either the county or city level who has to decide whether to activate sirens, the incentives are for you to err on the side of false positives. If you fail to sound the alarm in a particular area that is affected, you're toast.

    The proper response to sirens and NOAA weather radio alerts is neither to ignore them nor to run screaming for your basement. Instead, check the radio for details and make an intelligent decision once you know them.

  2. If NOAA weather radio can do this with SAME alerts, why can't counties and municipalities do this with their own sirens?

    I work for a company that does software for public safety. We've done multiple interfaces with devices which tone out certain fire departments, reads a message over the loudspeakers at a station, and opens the garage doors so they don't have to. If that kind of thing can be automated, why can't storm sirens?

    Our city has sounded sirens twice this year when high winds were in the area. I spoke with out police chief about this and he said that the sirens are outdoor warning sirens, not simply tornado sirens. I understand that the government can make this distinction themselves, but the citizenry won't. They hear sirens and they think tornado. When that doesn't come to fruition then the next time they will ignore them.

    The technology exists to sound sirens based on the warning polygons that are issued by the NWS. It's as simple as saying here is the affected area, is this siren within the area, and if yes, sound it. As with anything, someone to monitor it would be needed as well.

    The sirens can be another line of support in severe weather, but not if they are overused.

  3. David Van BergenMay 25, 2011 at 11:33 AM

    I understand what everyone is saying here and I agree with the comments. I do think the technology is available to do selective sounding of the sirens. That certainly would cut down on the excuse of "they use the sirens too often and we don't know when it is real or not." Of course that excuse is bs as stated above since once they are sounded one should tune into media to determine what action they need to take.
    Here in Houston we don't have that problem. We don't have any sirens. I wish we did!!

  4. BTW, this is not hypothetical for me. A storm is moving north through JoCo right now that has spawned tornadoes and is headed right for me. I know because when my NOAA radio went off, I tuned into local news for detailed updates.

  5. AccuWeather sells one of my inventions what automatically compares the NWS tornado warning polygon and triggers the sirens in the polygon and adds sirens very near the polygon.

    It simply says to the EM or dispatcher: Do you wish to active sirens? If yes, the sirens selectively activate. It is no more complicated to the dispatcher than the current system.


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