The Fujita scales have served us well, but it is time to move on

Destruction left behind the Quad-State Tornado

As I write this, it has been roughly three days following a devastating tornado outbreak across the midwestern and southeastern United States. While not yet confirmed, there appeared to be a record-setting tornado that stretched from northeastern Arkansas, across southern Missouri, western Tennessee, and across Kentucky, where recovery operations are ongoing and the death toll climbs every day.

This “quad-state” tornado with destruction on this scale creates complications for meteorologists who are tasked with evaluating the tornado post facto and assigning it a rating. They cannot get in the way of emergency operations. The destruction covers such a large area of land that evaluating it all takes time.

But one key reason that’s holding up the official rating of this historical tornado is that engineers need to evaluate the destruction to determine if the tornado is worthy of the high EF4 or highest EF5 rating.

If that seems weird to you, there is a reason why.

Why tornado ratings matter

Ultimately, the rating is irrelevant to the nearly hundred who are dead, or the thousands who have lost their homes, business, family members, or friends. No rating will change the impact on their lives.

Society has largely agreed that disasters and natural events need to be measured and compared on a variety of levels. Tornados, hurricanes, nuclear incidents, earthquakes, even solar events all have some form of a sliding scale of severity to stack similar events up against each other. It’s important for historical context, future research, and developing safer societies.

Tornados are difficult to rate. They’re very dangerous to approach in almost all situations. Their relatively narrow track means placing anemometers and barometers in the path of a tornado is logistically challenging (especially in Tornado Alley where road networks are not ideal for quick traversal, or Dixie Alley where dense forestation and the terrain limit visibility).

Instead, tornados are rated after the storm has occurred. For decades, we used the Fujita–Pearson scale, ranging from F0 (the weakest and most common) to F5 (the strongest and most rare). Developed by Ted Fujita, the Fujita scale estimated wind speeds based on the damage left behind. An F0 might have blown down some trees with estimated winds between 40-72mph. An F5 would leave the landscape completely barren with wind speeds exceeding 261mph.

However, as the decades progressed, research revealed that the wind speeds required for the damages described by Fujita were actually lower. Additionally, the Fujita scale had the inherit flaw that it treated all buildings the same; a poorly-built, wood-frame house that was swept off its foundation was treated the same as a brick and steel structure also swept off its foundation.

This is obviously problematic.

Enter the Enhanced-Fujita scale, a.k.a., the EF-Scale.

The EF-Scale sought to estimate wind speeds using 31 means of measuring damage, called Damage Indicators (DI). These DIs gave meteorologists in the field the ability to more precisely estimate wind speeds based on a combination of specific observations. The EF-Scale was adopted in the United States in 2007.

Since then, the new rating system has been met with some public scrutiny. In general, I feel public opinion in scientific matters is largely unfounded. To quote a line from Men in Black, “A person is smart. People are dumb, panicky dangerous animals and you know it.” Yes, this quote is about aliens, though it is largely accurate for most topics in public discourse. However, I think the public has a point here. After a decade and a half of the EF-scale, its flaws have been demonstrated several times over, none more so than the 2013 El Reno tornado.

The 2013 El Reno Tornado

The El Reno, Oklahoma tornado was a behemoth of a funnel. At 2.6 miles across, it had the widest damage path ever recorded, and at 302mph, the fastest winds ever recorded on this planet. Not estimated, recorded by field instruments. The tornado had an irregular direction of travel, exasperating its dangerousness. It claimed the lives of eight people, including respected meteorologist Tim Samaras, his son Paul Samaras, and research partner Carl Young.

It was rated an EF3.

Why? Because it hit an open field. There just wasn’t enough human infrastructure destroyed for the historical tornado to earn the EF5 rating.

The public — as I just did — points to the El Reno tornado as the shining example for why the EF-scale is flawed. It matters because the El Reno tornado has been classified alongside the relatively-moderate March 2020 tornado that went through Nashville. That does not make sense to me, and it does not make sense to many others. Historical context is muddied by the EF-scale.

Let’s create a hypothetical. Let’s say you were to observe two identical tornados with the same characteristics on radar, had the same visual appearance, and had identical wind speed and pressure readings. However, one tornado hit an open field. The other tornado leveled a suburban neighborhood leaving nothing but wood splinters and twisted metal. These two tornados would be rated differently according to the EF-scale. Help me understand why that is acceptable.

Now here we are, anticipating the Mayfield / Quad-State tornado rating like some kind of an unpleasant and terrible contest. There’s this odd sense that it will not be rated an EF5 and that is somehow an injustice. To whom is it an injustice? Not the victims, as I already said; the rating is irrelevant to them. Maybe a high rating would give answer to the “why” questions of someone who is grieving. Maybe a high rating will help justify the ruins in rural western Kentucky. I don’t really know the real reasons why the public wants an EF4 or EF5 rating, but I know that what I saw on radar and the devastation we have all seen in pictures indicates that this was a rare, powerful, and deadly tornado, and it should be rated as such.

Screenshot from GR2Analyst of the Quad State tornado over western Kentucky.

We need a new scale

I believe that the Fujita scale, both the original and the enhanced version, have served their purpose but no longer meet the needs of our current society. I am proposing a new system that throws out the numerical rating system and examines a tornado in two categories:

  1. Meteorological Significance — The observed or radar-indicated wind speeds, shape, size, etc.
  2. Impact on Life, Limb, and Property — The human toll and devastation caused.

The Fujita scale has attempted to lump these two categories together. While that may have worked for most tornados, there are numerous examples that demonstrate correlation does not equal causation. Massive, high-wind tornados are not always devastating. A weak-to-moderate tornado can devastate. These are independent factors and should be treated as such.

This new scale would be a two-dimensional matrix, as such the two rating parameters could be independently located on the X- and Y-axis. It answers the two questions that are at the heart of all rating systems: How powerful was the tornado? How much damage did the tornado cause?

The controversial rating of the 2013 El Reno tornado would be better communicated by this matrix. Instead of “EF3”, it would be rated “Meteorologically extreme with a medium impact.”

One immediate criticism I anticipate in this system would be a lack of numerical representation. Numbers are unambiguous in their hierarchy. The Storm Prediction Center (SPC)’s categorical outlooks are often criticized for their ambiguous use of “light”, “enhanced”, “marginal”, etc. In fact I’m not even sure if I typed those in the right order without looking up the scale the SPC uses.

I am not set on this naming convention, or any naming convention for that matter. If it is determined that maintaining numerical scales for clarity purposes is the best direction, then so be it. The El Reno tornado could be labeled “5×3”, “5.3”, “Met 5 Impact 3”, “Class 53” or whatever.

Note that I am not defining what would constitute a 1 or a 5 or a 3 on either axis; I will leave that up to the men and women with superior knowledge and experience in the field. This is just my suggestion for something better.

This system would have an added benefit on the real-time warning system. Meteorologists charged with the responsibility of communicating to the public can leverage this scale in real time to stress the urgency of the threat. High resolution radar, a larger array of observation systems, and a robust network of trained storm spotters means our ability to see how power a tornado is in real time is far greater today than it was just a decade ago. This will no doubt be controversial, but there is ample discussion about how to stress to the public that they need to take action when a threat is imminent. People would jump at the idea that something rated a “5” or “Extreme” is approaching. Some have considering telling the public that, for example, “a probable EF5 is approaching.” The Fujita scale was never designed for this and this practice is frowned upon. However, the immediate meteorological observations can be communicated on a scale that is easily understood and immediately actionable. I’ve seen one of my local news stations attempt something like this during their tornado coverage, but a standardized approaching would be better.

The way we rate tornados will not change what happened, but it can change the public perception and how we react to and study the societal impact of these deadly storms.

There are a variety of ways you can help out in Kentucky. WFPL is keeping an updated list on places acceptation donations for tornado victims, including the government of the Commonwealth of Kentucky.

(Cover image AP Photo/Michael Clubb)