Tornado Warnings- they strike fear in many people, but others have reached a point where they’re no longer fazed by them. We’ve all experienced it- a Tornado Warning is issued, we take shelter, and nothing happens. In fact, that’s the case roughly 76% of the time. According to the National Weather Service, only 24% of all tornado warnings are observed with a tornado or tornado damage afterwards.
Tornado Warnings are issued when the threat of a tornado is imminent, whether Doppler radar has detected strong rotation, or an actual tornado or funnel cloud has been reported to the National Weather Service. Either way, if your area is listed in the warning, you are in danger.
Let’s face it: false alarms will ALWAYS happen, but the NWS has been working hard, though maybe not hard enough, to limit how often false alarms happen. In October of 2007, the NWS implemented a new method of issuing warnings- basing them on polygons rather than entire counties (see Figure 1). Storm-Based Warnings show the specific meteorological threat area and are not restricted to geopolitical boundaries (county lines). By focusing on the true threat area, warning polygons improve NWS warning accuracy and quality. Storm-Based Warnings promote improved graphical warning displays, and in partnership with the private sector, support a wider warning distribution through cell phone alerts, pagers, etc.
Although this is a great start in lowering the number of false alarms, it still happens, and it happens a lot.
In the United States, the vast majority of all tornadoes are weak and short-lived, on the ground for a very small amount of time. EF-0 tornadoes account for 59.83% of all tornadoes, while EF-1 tornadoes make up 28.48%, EF-2 tornadoes with 8.66%, EF-3 tornadoes with 2.45%, EF-4 tornadoes with 0.54% and EF-5 tornadoes making up 0.04% of all tornadoes in the US.
A large number of weaker (EF-0 and EF-1) tornadoes occur from Quasi Linear Convective Systems, basically a long line of severe storms stretching from southwest to northeast. These systems have been known to produce stronger (EF-2+) tornadoes, but that isn’t common. With these systems (and in general), tornadoes can quickly spin up, making advance and accurate warning difficult. In these situations, with particular QLCS systems that have a high chance of producing tornadoes, NWS offices will often issue Tornado Warnings with massive TOR (Tornado Warning) polygons that can cover hundreds of miles (see Figure 2), which has a huge, negative impact on the accuracy of warnings, because a massive number of people will experience a false alarm.
As stated before, the tornadoes produced by these systems are usually (though certainly not always) relatively weak, and those tornadoes do not pose a major threat to life (EF-0 and EF-1 tornadoes account for only 8% of all tornado deaths from 1986-2010). On top of the relatively small (relative compared to EF-2+ tornadoes, which account for 92% of all tornado-related fatalities) threat to life, tornadoes in these systems are harder to predict and pinpoint. As a result, many NWS offices have suggested and even started implementing a system of not issuing TORs for such events- only SVRs (Severe Thunderstorm Warnings) that mention the possibility of brief, rain-wrapped tornadoes. Not only will this cut down on the number of TOR false alarms, it will also give fair and advance warning of the possibility of brief tornadoes.
Because of the measly 24% success rate of tornado warnings, many have become complacent, with a mindset of “it won’t happen to me,” or “it never really happens.” This mindset has caused countless deaths and is likely a factor that played into the high number of fatalities in the May 2011 Joplin, MO tornado and the Super Outbreak in the Southeast in April 2011.
As a result of these incidences, the Joplin tornado in particular, several NWS offices have adopted a new Tornado Warning strategy, called “impact-based warnings.” These warnings use very strong wording to communicate the expected dangers and results of specific tornado-warned storms (Figure 3).
For example, most tornado warnings have been (and still are in most states) worded something like this:
The National Weather Service has issued a Tornado Warning for western —- County in —–, until 5:45 pm EDT. At 4:47 pm EDT, NWS radar indicated a severe thunderstorm capable of producing a tornado near —-, moving northeast at 50 mph. Locations in the warning include —-, —-, —-, and —-. Precautionary/preparedness actions: take cover now. Leave mobile homes and vehicles. If possible, move to a basement or storm shelter. Otherwise, move to an interior room or hallway on the lowest floor, away from windows and outside walls.
The impact-based warnings are more strongly-worded, and do a better job of communicating threats associated with a storm. Here’s an example (this type of wording would have been used with the Joplin tornado, had this system been implemented before):
The National Weather Service has issued a Tornado Warning for —– County in —-, until 6 pm EDT. At 5:04pm EDT, a confirmed large and destructive tornado was located near —- and moving northeast at 40 mph. This is a particularly dangerous situation. Hazards… deadly tornado and baseball size hail. Source… spotters and law enforcement confirmed a tornado with significant damage reported in the — subdivision. Impact… life-threatening situation. You could be killed if not underground. Complete destruction of homes and buildings will occur. Tornado… observed. Damage threat… catastrophic.
See how you’d be more likely to heed the second warning versus the traditional first warning? These warnings went into effect in 2012 and are currently used in 14 states: Colorado, Illinois, Indiana, Iowa, Kansas, Kentucky, Michigan, Minnesota, Missouri, Nebraska, North Dakota, South Dakota, Wisconsin and Wyoming.
To understand the decision-making process that happens in the minds of the public when TORs are issued, a researcher at Oak Ridge National Laboratory helped conduct a phone survey of more than 600 people in Oklahoma, Kansas, Minnesota, Illinois, Mississippi, Tennessee and Alabama, who lived in areas struck by tornadoes in 2008 and 2009. According to data collected, when asked whether respondents took any action to protect themselves, their families or their property when a TOR was issued, 59% said yes and 41% said no.
41% took no action whatsoever.
The survey also found that 40% said they took shelter after hearing a warning, but 11% looked for more information, 2% called others, 6% protected private goods and 5% continued doing what they were doing. When asked whether they went outside or looked out a window to verify whether a tornado was coming, 67% of respondents said they did.
That’s because people innately tend to look for confirmation that a tornado is actually happening, whether in the form of a phone call from family or friends, warnings from neighbors or, all too often, an urge to get a glimpse of the tornado in real time. Once they have that secondary information, they’re much more likely to take shelter, but there are problems with these options. Waiting for a tornado to appear shaves precious minutes off of the warning time window (the average lead before a tornado touches down is about 13 minutes). If that tornado ends up touching down directly on your house, it’ll be too late to react, and if it’s raining, it can be impossible to see a tornado coming until you’re practically in it.
The survey also concluded that many people could not describe the difference between a Tornado Watch and a Tornado Warning.
Having said that, the NWS often gets blamed for the false alarms, which aren’t necessarily their fault- the technology to confirm a tornado forming or on the ground simply doesn’t exist. Never mind the fact that the warning has to be issued before the tornado itself begins forming, as to warn those that are directly beneath the descending funnel and in the immediate path.
The most important thing to remember regarding TORs is this- when a TOR is issued, that means the NWS has a moderate to high level of confidence that a tornado will form, is forming, or has already formed in a particular storm. Remember, radar only shows rotation- not an actual funnel or tornado (Figure 4). Whether that area of rotation drops a tornado or not shouldn’t necessarily reflect upon the NWS who issued the TOR, although it can be a learning tool for weather professionals.
The bottom line is this: yes, there are false alarms, and yes, they are common. BUT, a TOR is never issued for no reason- if a TOR is issued and you are in the area of the warning, you are likely in danger, whether it be from the possibility of a tornado forming soon or a tornado already on the ground. No matter how many false alarms you have experienced or think you have experienced, taking 20-30 minutes of your time to seek shelter and take proper precautions when a TOR is issued isn’t going to kill you- not taking those precautions very well could.