Sunday, June 26, 2011

Why the Weather Channel's TOR:CON index is humbug

I live in the Central Time Zone of the United States where severe weather is relatively common. I have a NOAA weather radio because I do not want to be killed in my bed at night by a tornado. I am also an anxious person. Lately, the focus of my anxiety has been the weather. So I am part of the Weather Channel's key demographic: Persons Who Are Easily Terrified.

Today, there is a chance of severe thunderstorms from Northern Minnesota to Nebraska to Northern Mississippi, Alabama, and Georgia. Damaging winds, hail, and isolated tornadoes are the "primary risks" for persons living in this large portion of the lower 48. This no mere chance of severe weather: the Weather Channel describes it as a "Weekend Storm Threat." Chances of severe weather are often described as threats in order to make the consumer of Weather Channel products feel more threatened. Those feeling threatened are more likely to compulsively consume Weather Channel products so as to "track" and "stay on top of" any severe weather that may or may not develop.

One Weather Channel product designed for this purpose, I believe, is the TOR:CON, or the tornado condition index. According to the Weather Channel,
The TOR:CON values range from 0 to 10. A value of 4 means that there is about a 40% chance of a tornado within 50 miles of a location in the specified area of severe thunderstorm activity. This also means that there is a 60% chance that a tornado will NOT occur.
I have a habit of freaking out when the TOR:CON values for my area are high. But I've thought about it, and I believe that I have no good reason to, even when the TOR:CON value for my area is a whopping 10, or a 100% chance of a tornado within 50 miles of my location.

A TOR:CON value is really the probability that there will be a tornado within a circular area with a radius of 50 miles. The area of a circle is π multiplied by the radius squared. So such a circular area measures approximately 7,854 square miles. Now, consider a worst-case scenario: a mile-wide EF-5 tornado traversing this circular area through its center and thus on the ground for a hundred miles. The area flattened by this tornado would therefore measure 100 square miles. If we divide 100 by 7,854, we obtain .0127. Therefore, if we assume that the TOR:CON for the area in question is 10, there is a 1.27% chance that a person in the area in question will be in the path of such a tornado. Is this something that a rational person should worry about? I don't think so.

Now, if you tell someone, even someone like me, that there is a 1.27% chance that I will be in the path of a tornado, that person will not respond with the trepidation required to keep him or her glued to The Weather Channel for the very latest updates on a very dangerous severe weather threat that could destroy everything in its path. Why, it could happen tomorrow, you know!

I am neither a mathematician nor a meteorologist. My analysis is admittedly overly simplistic. So, for example, perhaps my line of reasoning erroneously assumes that if there is a tornado in the area in question, there will be only one. But we all know that tornadoes often occur in bunches. What I think my reasoning accurately shows, however, is that the TOR:CON is inherently and deceptively alarmist. In order to get sufficiently worrisome TOR:CON values, one must increase the size of the area in question from, say, the square mile in which my house is located to a 50 square mile area with my house at its center. I think people like me (i.e., mathematically unsophisticated and unusually anxious) make a fallacious inference: for example, we infer from the fact that the TOR:CON value is five that the chance that a tornado will affect our neighborhoods is somewhere around 50 percent. And it obviously isn't.

This is only one of the reasons why I hate The Weather Channel.


  1. You say humbug, I say hokum.
    Also? I envy your tireless commitment to reason and seemingly effortless talent for writing. And while I most certainly believe this Weather Channel's TOR:CON & virtually all other devices used by media to reinforce the need for the product they are selling are total farce, I'd never take the time to think it through to this extent. I enjoyed reading this very much.

  2. Thank you! I am happy to hear that you enjoyed it. By the way, I agree that "hokum" is the better word here.

  3. Wow thanks for breaking that down I'm terrified of bad weather

  4. the world is a stage. tornadoes don't even occurr naturally. the world is nothing like we have been brainwashed to believe it is. the weather channel is just another portion of the government/big business world and donald trump is a loser!

  5. Thank you for your comment. I agree with you, except that I don't know how tornadoes could occur unnaturally. You lost me there.

  6. I think the torcon index is more of a pay attention index. If there is a high torcon index, the weather has a chance of turning ugly. Greg Forbes is a true expert in severe weather. So how can he drill down all of that information to alert people they need to pay attention to certain areas. Severe weather potential usually covers wise swaths of the country, especially in the spring. Greg Forbes simply says within these areas, not all potential risks are equal.

  7. Some of the on-air meteorologists define TOR:CON when they forecast severe whether, but not all of them do. One of them (it might have been Kelly Cass, but I'm not sure) gave a value on the air a week or two ago without mentioning that it represented a percentage chance of severe weather within 50 miles of a location. So it is easier for a viewer to jump to the conclusion that there will be a 40% chance of tornadoes in Wichita or wherever today. I didn't mean to suggest that Greg Forbes isn't an expert. I claim only that the TOR:CON is alarmist humbug in the way it is used by the Weather Channel. Thank you for the comment.


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It is wrong always, everywhere, and for anyone, to believe anything upon insufficient evidence. ---W.K. Clifford

Question with boldness even the existence of a God; because, if there be one, he must more approve of the homage of reason, than that of blind-folded fear. ---Thomas Jefferson