Storm-Based Tornado Warnings Reduce False Alarms and Hopefully Will Eventually Lead to Better Public Response


After experiencing a tornado in my hometown of Norman, Oklahoma, and hearing all of the stories of many people’s experiences during the event, I am very worried about the public’s general apathy toward tornado warnings and the resulting lack of taking any action.

What worries me? Many things, but my basic premise is that people do not respond because they perceive that most NWS tornado warnings are false alarms, i.e.,” I have lived through many tornado warnings without taking any action so why should I worry this time?”

I believe this lackadaisical response to tornado warnings is mainly caused by the perceived very high false alarm rate for tornado warnings, and there is something we can do about it now! The National Weather Service does a credible job of warning for tornadoes. Average lead-time between the issuance of a tornado warning has gone from zero minutes to 14 minutes in the past two decades mainly due to the use of the NEXRAD Doppler radar network and its capability to observe circulations in storms. But the false alarm ratio is still ~75%, meaning that 3 out of 4 tornado warnings do not subsequently have a tornado in them.

A second reason for the perceived high false alarm rate is the way that media relay information about storm warnings and how local emergency management activate sirens when tornado warnings occur.

The National Weather Service has been issuing their warnings (tornado, severe thunderstorm and flash flood) as “storm-based” warnings for many years now. That means that they do not issue warnings based on political boundaries (like cities or counties). Rather, the warnings are issued as polygons which precisely outline the area that the expert meteorological believes is in the hazardous path. Yet, many communities continue to set off their sirens for the entire city or county.

Also, warning graphics shown by local television meteorologists often show whole counties rather than the actual polygon warnings. And warnings provided by many “weather alerting” services alert for whole counties too.

So, can you imagine if 75% of tornado warnings are false alarms and if you also hear sirens, see graphics or get alerts every time a warning is anywhere in your county, (I get about 3 warnings from a county-warning based service for every warning that actually covers my location) then the total “perceived” false alarm ratio is nearly 90%. This is even a fundamental issue with traditional weather radios, which offer only county-based granularity even when equipped with the S.A.M.E. decoding technology.

We have a weather alerting app, called iMap Weather Radio, that alerts only if your location is within a NWS storm-based polygon. We have over 250,000 users of this app, and we have many testimonials about how we have saved people’s lives during tornados. However, our biggest complaint is: “I did not get an alert for the tornado/severe thunderstorm warning in my area even though the sirens were going off and the television meteorologist was showing I was in the warning.” We actually had to build a tool so that we could investigate each of these complaints……and guess what? EVERY single complaint we have received we have shown that the location of the person was actually NOT in the warning polygon even though they were getting alerts from multiple credible sources!

Two steps can be taken now to help address this issue. First, the technology exists to control siren networks in a way that only those within a warning polygon are activated. There should be an emphasis by federal, state, and municipal authorities to implement the use of such technologies. Second, media outlets needs to cease using county-based displays of warnings. These issues greatly accentuate the perceived false alarm rates that ultimately lead to lackadaisical response from the public!

Categories: Alerting, Severe Weather, Tornado | 3 Comments

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3 thoughts on “Storm-Based Tornado Warnings Reduce False Alarms and Hopefully Will Eventually Lead to Better Public Response

  1. Lak

    Absolutely agree here: more precise, personalized alerting systems will hopefully turn this around.

    Maybe your alerting app needs to have a visual that says “you are in the warned county, but you are not in danger”.

  2. Fred

    If some people don’t heed the warnings, too bad. What’s next, lead em by the hand???

  3. Dave

    Mike, I applaud the app and encourage more development along these lines. However, there are deeper issues for rural America. I live at the very edge of what I would call adequate cell coverage. There are numerous times I can’t get a reliable signal and the only dependable source for warnings is my weather radio. I have satellite internet and TV but they are useless when the signal is degraded by deep convection (I have no land phone line). One may consider the 75% false alarm number to be unacceptable but considering the handfull of actual tornado warnings most people get for an entire year this shouldn’t be that much of an inconvenience; at least I don’t think so. Even when there isn’t a confirmed tornado in the 75% cases, there obviously was a severe enough storm to get the attentionof the NWS meteorologists. That in itself should be enough to get peoples attention. I think there could be an improvement in the level of the tornado warning. Just like hurricanes, all tornadoes are not created equal. If warnings could provide a little more details on the severity of the tornadic storm that may help. I think the language used in the warnings a week ago was a good step forward. The storm a week ago in Woodward is a another example. The people who didn’t go to bed and kept watching the reports on television were prepared. Anyone who went to bed should have known the dangers were still there. The NWS did a good job in forecasting the development of the storms that occured after dark. I don’t know what else could be done to warn those who didn’t monitor the situation. I think people dwell too much on false alarms and it’s a pipe dream to think it will ever approach perfection. How do you help those who don’t heed the warnings and, unfortunately, make the ultimate poor decision that costs them their lives.

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