Showing posts with label siren policy. Show all posts
Showing posts with label siren policy. Show all posts

Friday, October 3, 2014

Recap of Oct. 2 severe weather, challenges faced, and a word on siren policy

Until last night, it had been a long time since widespread severe weather (not including biblical flooding events) had affected the Memphis metro. Tornado Warnings were last issued in late April. A well-advertised, and well-forecast, squall line moved through the region during the late evening hours bringing many reports of wind damage and several areas of rotation on radar. No reports of tornado touchdowns were received in the immediate area, though possible tornado damage occurred in northeast AR.

Every county in the metro was under a Tornado Watch and Severe Thunderstorm Warning as the line moved through and several areas were also under Tornado Warnings due to radar-indicated rotation in the fast-moving line. An early recap of the night from NWS-Memphis can be found here. They also discuss areas they intend to survey for storm damage.

Severe weather reports received by NWS as of mid-morning Friday. Most were wind or wind damage, though a possible tornado struck east of Jonesboro.
There are two main issues I want to address in this blog: 1) technology challenges and 2) outdoor warning siren policy.

Technology challenges

Technology. We love it for many good reasons. It allows us to do many things quickly and more efficiently than ever before. It allows us to push specific warning information to you via your smartphone almost as soon as it is issued by the NWS. But it also has its pitfalls. Namely when it doesn't work. Fortunately our critical warnings worked flawlessly last night, but there were other issues.

MWN StormView Radar on the website and mobile apps was one such problem. Due to multiple malicious attacks on multiple weather vendors' servers yesterday, including at least one big name and ours (though not targeting MWN directly), our radar stopped updating. The timing was awful. We apologize for and sincerely regret this major inconvenience; unfortunately some idiots like to "be funny" at other's expense. We're not laughing. If they can be tracked down, they ought to be prosecuted. We will be following up with our vendor on best practices going forward, but the outage was (and remains) completely outside of our control, though we take responsibility for providing the service to you.



In addition to radar issues, MWN headquarters lost internet connectivity as the squall line was moving across the river and Tornado Warnings were being issued (it also remains down this morning). This outage hampered our ability to disseminate information (including critical social media posts and data from our Bartlett weather station), monitor incoming data (including radar), troubleshoot the ongoing issues with our web radar, and communicate with the NWS. I'm not turning this into a bash-fest on our internet provider. This is the first outage we have had in months, perhaps over a year, and the connection handles everything we throw at it on a routine basis. The point is, once again, technology is not flawless and is subject to outage.

I want to take just a minute though to recognize MWN interns Kevin Terry and William Churchill for exemplary service last night as MWN's internet feed went down. Working from Mississippi State (there are advantages to working from disparate locations during severe weather events!), Kevin and William immediately took over nowcasting responsibilities in the middle of the event and didn't miss a beat. I'm guessing that most people watching our Facebook or Twitter feeds last night didn't know a major link in the chain had failed. That is a sign of a well-oiled machine and I thank them for their awesome work and dedication to all of you! My wife loaned her laptop to the cause (thanks honey!) and, courtesy of a smartphone hotspot, I was able to re-engage on a limited basis. Sometimes it takes a team effort and I've got one of the best in #TeamMWN!

Tornado Warnings and outdoor siren policy

The other discussion that needs to be had is regarding outdoor warning siren policies. Truth be told, it's been a relatively quiet couple of years for severe weather in the metro. Sometimes that "lack of practice" results in lack of preparation and awareness. The main issue we saw last night was in Shelby County, but the general principles apply most anywhere. Recall that Tornado and Severe Thunderstorm Warnings are not issued by county. They are "storm-based polygons," meaning they are drawn to reflect the forecast path of the suspect storm. Also recall that outdoor warnings sirens are for OUTDOOR use and aren't designed to be heard inside well-insulated homes with TVs and air conditioners on and storms overhead, and definitely not while you are sleeping. That being said, we recognize that many people are close enough to a siren to hear it indoors.

Siren policy differs by county, and in Shelby County it varies by municipality. The best siren policy is one that limits the activation to times when the community in the path of the storm is the only one alerted. To review, these are the policies in place in Shelby County as of October 2:

  • Bartlett, Collierville, and Germantown sound sirens for their cities (the entire city) only if the warning polygon intersects their respective municipal boundaries.
  • Shelby County sirens (including Millington, Arlington, Lakeland, and unincorporated areas of the county) sound for the entire county when any part of the county is warned.
  • City of Memphis sirens also sound for the entire city when any part of the county is warned.
  • However, Memphis is nearing implementation of a brand new system (the change should probably occur in November) that will activate sirens in Memphis only for those areas that are within the warning polygon, plus any sirens outside the polygon that can be heard within the polygon. Details on this policy change can be found here.

A Tornado Warning was issued at 11:13pm last night (shown below) that clipped the eastern side of Collierville. No other part of Shelby County was affected. In fact, the storms had exited all but the southeast corner of the county. However, given the above-stated current policies, sirens should have sounded in Memphis, Shelby County, and Collierville.  Bartlett and Germantown were not affected.

This was a case in which, under Memphis' new policy, sirens would NOT have sounded for any part of Memphis, which is exactly the way it should be. In our opinion, Shelby County should also move to a policy that allows segmentation of the sirens. There really was no reason to warn Shelby Forest, Millington, Arlington, or Lakeland about the storm in Collierville. I checked with Bartlett officials and sirens were not sounded in their city - well done! I also heard multiple reports last night that Collierville siren activation may have been delayed, and then continued after the warning for Shelby County was cancelled at 11:23pm (10 minutes after issuance). We can't corroborate that firsthand however.


Despite the sometimes untimely pitfalls of technology and some initial setup, the best way to receive warning information specific to YOUR location is smartphone weather apps with location-based warning technology. They can be set to warn specific points, regardless of county, and provide the most pertinent information to your location. Because of potential for technology issues, we also strongly advise a secondary means of receiving warning information that will wake you. The best secondary source is NOAA Weather Radio. Despite being county-based (all radios in Shelby County would have alarmed with the Collierville warning above), it's better than nothing, especially when you're asleep and local media is turned off in your home. Outdoor sirens are not to be relied on to wake you up.

We appreciate those who have trusted MWN and our StormWatch+ technology to provide the precision warnings described above. If you're interested in checking it out, click the appropriate link below. It's a fraction of the cost of a weather radio and only alerts you when necessary - plus it will wake you up in the event of the most severe storms. The precision is best demonstrated by an individual who lives on the west side of Collierville and indicated that StormWatch+ did not sound last night. As it turns out, he was less than a mile west of the warned area and not in harm's way. The technology worked as advertised.

To conclude, we thank you for your patronage and support of MWN, we apologize for the radar issues, and we greatly appreciate the dedication of #TeamMWN! If you have any questions, comments, or issues to raise, we would love to hear from you! Comment on this blog, hit us up on social media, or drop an e-mail via our contact form.

Erik Proseus, MWN Meteorologist

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Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
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Monday, September 22, 2014

New siren activation policy coming to the city of Memphis

In Shelby County, there are five entities responsible for outdoor warning sirens to alert the populace that a Tornado Warning has been issued for Shelby County. Those are the cities of Memphis, Collierville, Bartlett, and Germantown, plus Shelby County. Each of the four cities are responsible for warning systems within their municipal jurisdiction, while the Shelby County Emergency Management Agency covers unincorporated Shelby County outside the aforementioned 4 cities, plus the towns of Arlington, Lakeland, and Millington.

Municipal boundaries within Shelby County. Bartlett, Germantown, Collierville, and Memphis all activate their own outdoor warning sirens. Shelby County is responsible outdoor sirens in unincorporated areas, as well as Millington, Lakeland, and Arlington city limits (grey).

As has been discussed on this blog before, Bartlett, Germantown, and Collierville all sound their outdoor sirens based on an imminent threat to their particular municipality, using the Tornado Warning polygon (or warmed area) issued by the National Weather Service. The city of Memphis and Shelby County have warned their entire area of responsibility for a Tornado Warning that includes any part of Shelby County. That policy will be changing in the city of Memphis.

Under an agreement with American Signal (an outdoor warning siren manufacturer), a brand-new state-of-the-art warning system has been developed and is in a test phase at the Memphis Office of Emergency Management (OEM), a division of Memphis Fire Services, which is responsible for activation of the city's 108 outdoor warning sirens. This new system, with multiple layers of redundancy and the ability to be triggered manually from multiple locations including via mobile by key personnel, will allow the city to modify its policy such that only the portions of the city that are under a threat of a tornado will be warned. Using software automation, polygon notification to specific areas of the city will be possible, thus reducing over-stimulation and siren fatigue of the public and ensuring that those that hear an outdoor siren during inclement weather in or very near the warned area as defined by the National Weather Service (NWS). (Note that the new system has not been implemented and no date has been set at this point for implementation.)

Location of the city of Memphis' outdoor warning sirens on Google Maps.

So how will the new system work? The software will ingest weather alerts as soon as they are issued by NWS-Memphis. When a Tornado Warning is issued that intersects any part of the city of Memphis, sirens will be automatically activated by the software. The sirens that sound will be those within the NWS polygon/warned area, as well as those that can be heard within a portion of the warned area, even if they are outside of the warned area. This "buffer" will mean that some areas that are just outside the warned area could hear the sirens, but it will significantly cut down on the overwarning of the entire population when a small section of the city is affected.

In addition to the software-driven activation, sirens can also be sounded (in whole or in part) manually. All activities of the system are also logged and displayed on the user interface so that key personnel will know when and which sirens activated and whether each siren is in a functional state.

The approach taken by Memphis is a bit different from those in Bartlett, Collierville, and Germantown. In the new Memphis system, parts of the city may be warned, while other areas are not, due to the large geographic area within the city limits. In the other three municipalities, the entire municipality is alerted if any part of their city limits are within the warned area. This approach, while it may still result in some overwarning, is certainly satisfactory given the smaller geographic area that these cities cover.

At this time, we are unaware of any planned modifications to the Shelby County policy, which warns all of their area of responsibility for any threat to the county (meaning a Tornado Warning for Collierville would result in sirens sounding countywide). Shelby County is responsible for sounding sirens for areas outside Memphis, Bartlett, Collierville, and Germantown, including Arlington, Lakeland, and Millington.

Our take

I am strongly in favor of the more modern, and conservative, approach to warning that is now being developed by Memphis and is in place in the other three municipalities. It has been nearly 7 years since the National Weather Service transitioned from county-based warnings to storm-based polygon warnings for Tornado, Severe Thunderstorm, and Flash Flood Warnings. The goal was to offer more clarity on areas the storm would affect and warn fewer people, only those most likely to be in harm's way.

While media outlets and, more recently, smartphone apps like StormWatch+ properly warn only those who are within the storm's path (polygon), there are several warning methods that a vast majority of the public still rely on that do not have this capability, including NOAA Weather Radio and many outdoor warning siren systems. These systems MUST be upgraded to produce a consistent message across warning methods. While the NWS has done their part to attempt to reduce overwarning, technology must now catch up or the efforts of the NWS will be moot. Too many warnings, whether from true false alarms or "perceived" false alarms due to poor communication, result in complacency by the public who are then put in greater jeopardy of injury or death. We say "bravo!" to those communities who are addressing the issue with modified outdoor warning siren policies.  (Now it's time to get NOAA Weather Radio on board.)

Erik Proseus, MWN Meteorologist

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Follow MWN on Facebook, Twitter, and Google+
Visit MemphisWeather.net on the web or m.memphisweather.net on your mobile phone.
Download our iPhone or Android apps, featuring StormWatch+ severe weather alerts!