Tornado sirens

Factual Questions
1

It is that time of year. I am sickened by the devastation and deaths. I am still rational enough to ask how much good warning sirens do. Are we able to tell accurately enough when one is coming to warn people and does doing so save lives?

The local official have decided to sound their expensive toys every time severe thunderstorms are predicted. One day, I watched my neighbors continue their yard work, perhaps only with more haste, as the sirens sounded. I had realized before they started sounding, that a storm was coming. I went about trying to get as much done as I could before it hit. I am not about to go hide under the bed every time they cry wolf.

I have noticed in the debates over the sirens, there is never any comparison of deaths in places with and without sirens. I am all for things that will save lives, but want to see the beef.

2

they’re meant to tell people outside to seek shelter. Nothing more. Severe thunderstorms can turn ugly even w/o dropping a tornado.

the problem is that when you have intense tornadoes like we saw in Joplin, even people in shelter are at risk. A tornado that powerful is not going to care about sirens, houses, buildings, etc. it’s just going to knock them all to pieces and laugh at you as it goes on its merry way.

3

Predicting tornados is an inexact science, to say the least. If they could be predicted with any certainty, the death toll from the Joplin tornado would be zero, not 89 and counting.

Sirens are just that - a warning system. If you hear the siren, that means that shit is probably about to get real. Maybe a tornado, maybe not, but you stay outside at your own peril.

I’ve heard several thousand sirens in my lifetime, and for the most part I ignore them and go about my business.

4

Then, your local officials are clearly doing a disservice to their residents by overusing the sirens. I’ve never been in an area in which they were sounded for anything short of an actual tornado warning in the immediate vicinity.

5

I think he’s exaggerating a bit. I don’t know of anywhere that would set them off just because severe weather is “predicted.” In my area they get used for severe thunderstorm warnings (i.e. there’s a severe storm cell headed towards your area) and tornado warnings.

6

As jz78817 notes, if the tornado is powerful enough, even shelter may not save you. I haven’t yet seen an estimate of the Joplin tornado’s strength on the Enhanced Fujita scale, but all the reports show that it was a very large and powerful tornado.

Predicting tornadoes is inexact, but the NWS has gotten far better at spotting actual tornadoes (or storms which may spawn tornadoes imminently) in the past few decades, thanks to both Doppler radar and a network of trained storm spotters.

In short: if your area is under a tornado watch, keep an eye to the sky, and perhaps an ear to the radio. If, OTOH, your area is under a tornado warning, take it seriously.

7

Sirens started going off around here shortly after 6pm on Saturday. At first I thought maybe they were signaling the Rapture, since it didn’t look very stormy outside, but as it turns out they had issued a tornado warning for the NW corner of the county (about 15 mi from here).

What’s odd is that we had another storm come through about two hours later, much closer to us, with another tornado warning issued, and this time the county didn’t sound the sirens. So go figure.

8

sirens will sound when there is a watch (conditions are likely) will a couple minute of continuous sound. sirens will sound a warning (one has been sighted visually or on radar) with a couple minute of wailing sound.

the sirens are intended to aid people outdoors to be observant in a watch and to take cover (or be able to do so rapidly) in a warning.

weather radio (NOAA radio) in the USA can give warnings specific to a county if you have a radio equipped to do so (there is a unaudible data signal for location).

in the USA digital broadcast tv may have a station in your tv market that has a weather subchannel with continuous weather information from that local station.

tv stations and weather bureau will have overlapping radar and can track existing storms well and give advanced warning to locations in time to take shelter. tornadoes can be born and die in less than a minute so constant observation is warranted.

9

Out of curiosity, where do you live (i.e,. where is this being done)? I don’t believe that sounding the sirens for a weather watch is common practice – it’s certainly not done this way in the Chicago area.

10

I was gonna start a thread but maybe it’d be okay to ask here: Why all the deaths in Joplin? I’ve heard that a warning was issued 15-17 minutes before it hit. So why so many deaths? I understand that if you’re on the road or more than 15 minutes from shelter, you’re at greater risk, but 89 deaths? In an area where houses have basements and people know when the sky looks wrong?

What I’m looking for is reassurance that I’m safe in my basement under a heavy table or mattress.

Our town is getting a siren, and it will be sounded when there’s an actual tornado warning.

11

So nobody has any numbers?

12

you’re safest in that place. But in the path of an EF5 tornado, all bets are off. Your house isn’t even noticed by that kind of storm.

13

Around Columbus, OH the sirens only go on for a tornado warning, meaning one has been spotted.

I did a safety report on tornados just a few weeks ago and in doing so noticed that people have gotten jaded in respect to the sirens. On more than one occasion they’ve gone off at work and people went to the windows to check out the storm. Yes we are in a skyscraper, but tornados don’t care.

You could make the sirens shout, “Hey stupid! A tornado is coming and is about to kick your ass! Get inside and go to the basement!” and people would still ignore it.

Also, like people mentioned earlier, a tornado that can toss a train 100+ yards doesn’t care how far in advance you were warned or where in your house you’re hiding.

Personally, unless I’m already watching the weather and know where it is, I grab the family and head to the basement.

14

derp double post

15

They happen all the time here but we are out in the wilderness and can’t hear them so they auto-call us and tell us to turn on the TV for announcements. Hahahahahahaha, now that we have digital TV when there is a storm we don’t get TV reception. So we just keep watching netflix because if we lose the interwebs it might be an indicator that it’s time to go to the basement with the tuna.

If I stop posting after a major storm in the metro-east area of st louis just assume I was flattened while enjoying my favorite movie. :stuck_out_tongue:

16

OK, going back to your OP:

First of all, let’s make sure that you understand the difference between a tornado watch and a tornado warning.

A tornado watch means that the National Weather Service believes that conditions are favorable for tornado-producing storms to develop in the watch area. Watches are usually issued for fairly large areas, and for extended periods of time (hours, at least).

A tornado warning means that a tornado (or, a likely tornado) has been spotted in the area, usually in one of two manners:
a) Actual visual confirmation
b) A radar return which is consistent with the formation of a tornado
Warnings are issued for much smaller areas (often, only one or two counties, and even then, perhaps only parts of those), and for shorter periods of time. A warning is not a “forecast”, it is a report that a tornado is actually occurring.

As I indicated earlier, there have been improvements in tornado forecasting; according to this report, those improvements led to an increase in the average “lead time” for a tornado warning, from 6 minutes to 11 minutes (from 1994 to 2002). The report does not give an estimate for a number of lives saved, but common sense says that, if you have, on average, an additional 5 minutes to react and reach shelter, there must be some benefit in reduced casualties.

It sounds like there are (at least) two separate questions in here:

  1. Does the presence of tornado sirens save lives?
  2. Does compliance with tornado warnings save lives?

I don’t know, to what extent, tornado sirens cover the U.S.; I would imagine that most areas which are not within earshot of a tornado siren are lightly populated, and / or rarely suffer tornadoes, anyway, so I’m not sure if such data exist.

17

Twister? The Wizard of Oz?

We had the same problem with satellite TV. Seems like tornadoes are often preceded by heavy rain which knocks out the dish.

Everyone in our little town has a NOAA Weather Radio. (The city buys them.) They’re helpful, if you’re inside. You program them for your area and there’s battery backup. An alarm is sounded for watches and warnings, and you can also hit a button at any time to get a detailed weather report. They’re well worth the $30.

18

Tornado warnings have been surrounding my town for what seems like the last month. in fact there is one about 50 miles away, as I am typing this. But the sirens have NOT gone off in my town because my town as not had any tornado warnings.

Plenty of severe T-Storms, with quarter size hail in my town, but no imminent warnings.

My town knows enough to not sound the warning unless it a real threat of tornadoes. fortunately there have been none in the immediate vicinity.

19

Found some more info…

This blog shows a chart with annual tornado deaths in the U.S., normalized for population (in other words, it takes into account the fact that the U.S. population is bigger now than it was in the past):
http://www.norman.noaa.gov/2009/03/us-annual-tornado-death-tolls-1875-present/

It shows that the trend for the the death rate from tornadoes has actually been declining for quite a while. It’s difficult to point to exact causes for this decline, but improvements in weather forecasting and more effective methods for alerting people to tornadoes (sirens, but also TV, radio, and the Internet) undoubtedly play a role.

20

There are really three overlapping issues here.

The first being that a single tornado destroys an area usually ~1/4 mile wide wide by ~2 miles long. (Yes, some are bigger. The vast majority are smaller.) Yet the warning area is the size of a county, i.e. 20 x 20 miles or more. So even if they sound the sirens only when a tornado is actively on the ground tearing stuff up, somebody standing in any random spot in that county has much less than a 1% chance of being impacted by that tornado. (e.g. 0.5 square miles / 400 sq miles = 1 in 800 odds = 0.125%)

The second issue is that hiding in your basement is effective against EF3 and if you’re lucky, EF4. Unless you’ve got a hardened shelter in your basement, EF5 is probably gonna kill you. The good news is that historically, there are a thousand EF0s for every EF5. So the real baddies are pretty rare.

The third is, and the one directly relevant to Joplin & Tuscaloosa, is there is a lot of housing in tornado country which doesn’t have any effective shelter. If you live in a standard wood-frame construction 2 or 3 story apartment complex, there is nowhere to go. For an EF0 through EF2 most bathrooms in most units might be good enough. For an EF3 or EF4, a couple people will emerge mostly unscathed. For an EF5, nobody in buildings like that gets out in one piece.
The first factor means that for almost all people almost all the time, the sirens are a false alarm *for them *even if a tornado is really on the ground. If your local emergency management folks like to sound sirens for severe thunderstorms instead of actual tornadoes, then the effective false alarm rate gets even worse.

The second and third factors mean that for real bad tornadoes, accurate warning will reduce the death & injury toll some, but not a lot.
The logical solutions to these problems are to mandate actual tornado shelters in all residential & commercial construction. And to move control of sirens to the NWS and tighten down the size of warned areas to minimize false alarms. Whether these ideas are cost-effective enough to actually implement is a different matter. Safety costs money; money that could be spent on other, perhaps more beneficial things.

I know I don’t have THE answer. I do know that around here we have sirens sound often enough that I interpret them as “watch the radar & the sky & go about my business.” They absolutely do not mean “go hide in the basement for 30 minutes just in case we ‘win’ the 10,000 to 1 tornado-meets-house lottery.”