Tag Archives: wireless emergency alerts

Top 5 ways to get severe weather warnings

Indiana map showing Risks of severe weather between 9 a.m. ET Thurs., April 20, 2017 and 8 a.m. the following day. Source: National Weather Service Storm Prediction Center
Risks of severe weather between 9 a.m. ET Thurs., April 20, 2017 and 8 a.m. the following day. Source: National Weather Service Storm Prediction Center

This post was updated at 9:40 a.m. April 20, 2017

A large part of Indiana has a level two (out of five) risk of severe weather today (April 20, 2017) and this evening, according to the National Weather Service (NWS) Storm Prediction Center. The primary threat today is damaging straight-line winds or gusts of 58 mph or greater, but an isolated tornado cannot be ruled out in much of northeastern and east-central Indiana.

That makes now an especially good time for Hoosiers (and everyone else who lives in an area that ever receives severe weather) to make sure they have good ways to know about any warnings their local NWS offices issue.

So, here’s my list of the best ways to get tornado, severe thunderstorm and flash flood warnings. Continue reading

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.”

What’s the #1 source for national weather?

Amateur-run Facebook pages should not mislead readers into believing that their information is better than that of the National Weather ServiceShould a Facebook page run by amateur storm chasers promote itself as the best source for weather information? I can’t help but wonder how many (if any) naïve Facebook users foolishly rely on such pages for time-critical safety information, in lieu of the National Weather Service (NWS).

Recently, a Facebook page distributed the graphic above. I’ve blurred out identifying information, because who it was doesn’t matter to the point of this article. But the headline, “The #1 Source for National Weather” certainly caught my eye.

I’ve tried multiple times to contact the owners of the Facebook page that published that graphic. I sent a Facebook message and sent an email message to the email address on their website. I’ve received no response. So, all I know about them is what I see online.

From what I see, both the Facebook page and associated website are published by a group of amateur storm chasers, none of whom appear to have a meteorology degree.

In the U.S., only one source of weather information has the authority to issue the official watches and warnings that trigger weather radios, etc.

Don’t read what I’m not writing! There’s nothing wrong with an amateur-run Facebook page or website distributing interesting or important weather information. I do it all the time on Facebook, this blog, Twitter, etc. What I don’t do, however, is claim that my information is any better than others’.

Why? Because I don’t want anyone to assume that my blog, Facebook page or Twitter feed (or anyone’s for that matter) is a safe and reliable way to get timely, live-saving weather alerts, especially NWS warnings. Not even the NWS’ own Facebook and Twitter feeds are timely enough for that (yet).

That’s also why I consistently encourage readers – for their safety – to maintain timely access to NWS products (e.g. via NOAA Weather Radio, smartphone apps triggered by NWS products, Wireless Emergency Alerts, etc.).

All of us who publish weather information on social media and other Internet channels have a responsibility to inform and remind readers that in the U.S., only one source of weather information has the authority to issue the official watches and warnings that trigger weather radios, etc.: The National Weather Service. Likewise, we must not publish anything that could potentially mislead readers into believing that our social media feeds can keep them as safe as do directly received NWS warnings.

Our readers’ lives could depend on it!

What do you think? Use this blog’s comment function to let us know.