Tag Archives: tornado warnings

Last night’s tornado warning demonstrates why sirens aren’t your best alert source

The tweet above from Valparaiso University meteorology student and Fort Wayne resident Matthew Hayes points out something a lot of Allen County, Indiana residents probably don’t know. The county’s outdoor warning siren system is all-or-nothing. That means that when a tornado warning covers any part of the county, sirens sound throughout the county, which encompasses 660 square miles (making it the largest county by area in the state).

That’s what happened at about 9:06 p.m. last night, when the northern Indiana office of the National Weather Service issued a tornado warning that included a small part of southwestern Allen County. A very small part:

tor_polygon
The Aug. 15, 2016 tornado warning included a tiny part of southwester Allen County, Indiana (the triangle indicated by the arrow.
Maps showing the complete tornado warning polygon, with and without radar data. At the time of the warning, the radar-indicated tornado was over the town of Andrews, west of Huntington, moving northeast at 25 mph.
Maps showing the complete tornado warning polygon, with and without radar data. At the time of the warning, the radar-indicated tornado was over the town of Andrews, west of Huntington, moving northeast at 25 mph. Click the image for a better view.

The Fort Wayne-Allen County Consolidated Communications Partnership center dutifully followed protocol and activated Allen County’s outdoor warning siren system. People throughout the county who were close enough to a siren would have heard it sound. Presumably, this  included people 26 miles away in Harlan, where the storm wasn’t forecast to travel. See a map of all Allen County’s sirens.  Remember, sirens are designed for outdoor alerting only, but people can sometimes hear them from inside their homes, if their homes are close enough to a siren.

Ironically, if anyone was in the small part of Allen County that the warning covered, it is unlikely they heard a siren. The nearest operating outdoor warning siren is at least four miles away, at the headquarters of the Southwest Allen County Fire Department on Indianapolis Road.

The outdoor warning siren nearest the warned area was at least four miles away, at the Southwest Allen County Fire Department station on Indianapolis Road.
The outdoor warning siren nearest the warned area was at least four miles away, at the Southwest Allen County Fire Department station on Indianapolis Road. Click the image to see a larger version.

So, last night’s tornado warning demonstrated two weaknesses of outdoor warning sirens as primary means of learning of such warnings:

  1. Outdoor warning sirens cannot be heard in many parts of Allen County, even by people who are outdoors.
  2. Sirens are often activated where warnings are not in effect.

What should you do? For geographic precision, your best bet is a good smartphone app, like Storm Shield or Weather Radio. These apps use your phone’s GPS to determine whether it is within the actual warning area. The next best thing is the Wireless Emergency Alerts that are built into  modern smartphones. As I explained in another blog post, the geographic precision of such alerts is imperfect, but it’s better than countywide, doesn’t require installing an app, and it’s “on” by default on modern smartphones.

When you’re home, weather alert radios provide very reliable alerts but have the disadvantage of alerting an entire county for any warning that includes any part of that county. At least weather radio alerts — unlike outdoor warning sirens — come with voice messages the explain what part of the county is affected.

The bottom line, as I’ve written before, is don’t rely on tornado sirens. Not hearing one does not mean you don’t need to take cover, because you might be in a place where it’s impossible to hear a siren. Hearing one does not necessarily mean you need to take cover, because your neighborhood siren might sound for a warning that doesn’t affect you. Find a better way to know if you are in danger!

Side note: Based on what I know about how the National Weather Service generates warnings, I highly suspect that the meteorologist who issued last night’s warning probably intended to keep the warning polygon out of Allen County entirely, but accidentally overshot the county line when drawing the warning polygon.

The truth about wireless emergency alerts

All national commercial mobile service providers (CMSPs) in the U.S. do their best to approximate National Weather Service warning polygons when relaying tornado warnings through the wireless emergency alert (WEA) system, according to an executive of CTIA, a wireless industry trade group. The result is geographic targeting that is more granular that the county-wide targeting of NOAA Weather Radio. And the industry is considering proposals to further improve the geographic targeting of WEA.

Information that CTIA assistant vice president for regulatory affairs Brian Josef provided to “W9LW’s Ramblings” contradicts a graphic that appeared on Twitter April 6 (below).

The graphic in the tweet originally appeared in a 2013 blog by WeatherCall, a company whose sales pitch includes pointing out shortcomings of WEA and other warning modalities. The tweet and blog post claim that wireless emergency alerts get sent by every CMSP tower in every county covered by a warning polygon, thus providing irrelevant warnings to more people than would receive the warning via NOAA Weather Radio.

Brian Josef, Assistant Vice President for Regulatory Affairs, CTIA
Josef

This might have been true when WEA was first implemented in 2012, the CTIA’s Josef told this blog. And to this day, federal regulations for WEA continue to permit the practice of alerting entire counties. But shortly after WEA was implemented, carriers found ways to improve the granularity of alerts. Today, every national carrier geographically targets tornado warnings based on NWS polygons, Josef said.

The system remains less than perfect, however. The most common way carriers target the reception of WEA messages is by broadcasting them only from the towers that are physically located within the warning polygon, according to a 2015 report by the Johns Hopkins University Applied Physics Laboratory.

In the graphic example below, black hexagons represent the coverage areas of one carrier’s cell towers (in reality, coverage areas are not hexagonal) and the black dots in the center of each hexagon represent the towers themselves (in reality, towers are not usually spaced so evenly). The red polygon represents the boundary of an example tornado warning. Green hexagons represent the areas that would receive that warning via WEA, if the carrier sends it only via towers that are located within the polygon.

Selecting cell towers (black dots) within a tornado warning polygon (red) is the most common way mobile carrier geographically target wireless emergency alerts, according to a Johns Hopkins University study.
Selecting cell towers (black dots) within a tornado warning polygon (red) is the most common way mobile carriers geographically target wireless emergency alerts, according to a Johns Hopkins University study. W9LW graphic.

As you can see in the graphic above, people in the white areas inside the red polygon will not receive the warning, even though the warning includes their locations. People in green areas outside the red polygon will receive the warning, even though the warning does not include their locations.

“There’s always going to be some overshoot, there’s going to be some undershoot, but they’re trying to employ the techniques that best approximate that alert area,” Josef said of the mobile phone carriers.

Researchers at Johns Hopkins University suggest a new, more precise geo-targeting method for wireless emergency alerts in a report published last June that the U.S. Department of Homeland Security commissioned. It proposes arbitrary-size, location-aware targeting (ASLAT), through which carriers would broadcast an alert over an area larger than the warning polygon and individual mobile devices would determine whether to display the warning, based on each device’s own calculation of its location.

ASLAT would require some changes to existing WEA standards, cellular network functionality and mobile device behavior. Josef stressed the importance of assuring that any new targeting technique not increase data congestion on cell sites at a time when weather conditions would already increase device usage.

“The carriers are constantly looking at ways to further refine and enhance geo-targeting techniques,” Josef said. “We also want to make sure we don’t endanger what has been a successful service.”

Better alternatives to tornado sirens

Photo of outdoor warning siren with superimposed text "For outdoor reception only"Earlier, I wrote a post titled, “Stop believing in tornado sirens.” I hoped it would help convince readers that the decades-old technology is not the best way to learn of severe weather threats.

Now, here’s a bit more about better alternatives.

Weather alert radios

Photo of weather radioIn the earlier post, I mentioned weather alert radios. There are several manufacturers and models. What you want is one that supports Specific Area Message Encoding (SAME). It’s a system that allows weather radios to remain silent until a warning is issued for your own county. This means there’s never any reason to turn off the radio. One of the least expensive is the Midland WR120. I’ve seen it priced at under $35. It’s available at most Walgreens pharmacies, as well as other local retailers. There are plenty of other choices. Just do a search on Amazon or any other shopping website for “weather alert radio same.”

Smartphone apps

Logo for American Red Cross tornado appSmartphone apps are another option. They have the advantage of using the phone’s GPS to know where you are and alert you of warnings for that location, even when you’re away from home. Be sure to choose an app that make a loud enough noise to wake you. One free option is the American Red Cross Tornado App for iPhones and Android phones. I have not tried this app but its description indicates it sounds a loud siren when the National Weather Service issues a tornado or severe thunderstorm warning.

Sample warning as displayed by Weather Radio app. Image provided by WDT
Sample warning as displayed by Weather Radio app. Image provided by WDT

I have used Weather Decision Technologies’ Weather Radio app. It’s also available for iPhones and Android phones but costs $4.99 (down from an earlier price of $9.99).

I’ve also tested the Storm Shield App from the E.W. Scripps Company. It’s also available for iOS and Android. Its price is $2.99.

Although they’re not free, both apps do much more than the free Red Cross app. For example, you can configure them to sound off for a variety of warnings, not just tornado warnings.

All three apps use the phone’s GPS to determine whether the phone is within the polygon that describes the specific warning area. If the phone is outside the polygon, the apps remain silent. This means you get no alarms for storms that might be in your county but will never affect you.

Wireless emergency alerts logoBy the way, if you have a new enough smartphone, it probably supports Wireless Emergency Alerts (WEA), which means that even without installing an app, the phone will sound off when a tornado warning is issued for wherever you are. It depends on the device and the cell phone company. My old iPhone 4 did not support WEA, but the newer iPhone 4S does. Follow the link at the beginning of this paragraph to find out if your phone supports WEA.

I know of no other options that will wake you in the middle of the night. But during the daytime and evening when you’re still up, the following resources can be helpful:

Text messaging

Many local TV stations send subscribers text messages when the NWS issues weather warnings. Just visit the website of your favorite station to see what it offers.

Other websites also offer text messaging, some for free and some for a fee, including:

Not that if a storm destroys your nearest cell phone tower, that might keep you from getting text messages on time.

Local broadcast radio and television

If you know a watch has been issued, you can learn of warnings by keeping a radio or TV on and tuned to a local station. Most will automatically interrupt programming when the NWS issues a warning for their listening/viewing areas.

Social Media

Local broadcasters and the NWS often post news of weather warnings on Twitter and Facebook. Social media, however, should never be your primary source of warning information, because warnings might not appear promptly enough.

Know someone who could benefit from this information? Use the sharing buttons below to share it with your own social networks. Feel free to submit a comment if you have other suggestions for weather radios and/or other sources of severe weather information.