"Violently" removed from official AMS definition of tornado

Dan Robinson

Dan Robinson

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In recent years, the "official" definition of a tornado (in this context, from the AMS Glossary) has been revised. One of these was to remove the word "violently":

http://glossary.ametsoc.org/wiki/Tornado

Other revisions to the definition are discussed in this paper "A Revised Tornado Definition and Changes in Tornado Taxonomy" by Ernest M. Agee:

https://journals.ametsoc.org/doi/abs/10.1175/WAF-D-14-00058.1

I can't find much about this other than the journal article linked above, but I am assuming the reason was that many weaker tornadoes didn't meet the "violent" criteria in the previous definition.
 
No, my point is the meaning of "violent" is subjective and arbitrary. According to previous definitions, 65 mph must have been considered "violent" because it was the bottom of the EF0 wind speed range, and if a tornado was classified as a tornado, then even if it was rated EF0 it apparently, by definition, would have had to have had wind speeds of at least 65 mph. But what do you call a similar vertical vortex attached to a cumuliform cloud that produces winds less than 65 mph? Was that not violent? Who says what is "violent" and what isn't?
 
That's what I meant - originally "violent" probably meant something capable of damage, but I don't know that for sure as I've never seen the backstory of how that original definition was settled on. Contemporarily, "violent" is only used in the context of F4+ tornadoes, so it makes sense for them to remove something that's subjective at best and conflicting with another usage of the term at worst.
 
As the science advances, definitions will naturally become more specific. It's just a natural part of evolution.
 
I've always thought of "violent" as meaning EF4/EF5, and previously F4/F5. There is also the buzzword "violent", which is exemplified by the motion visible in a "digger" or a "drillbit". When I think "violent motion", I think the early-in-cycle video of the Jarrell TX 1997 tube. That was some "violent" motion.

Also, way overuse of "quotes" in this post.
 
I'd be interested in seeing a scientifically precise definition. The scale of the circulation in relation to the top wind speed seems pretty important to me for classifying low-end events. It doesn't seem like a trivial question to me.

One case in August 24, 2016 in my home town of Grand Rapids Michigan was interesting. It was a mostly unpredicted marginal event with low-CAPE and low-LCL. A tornado generated a short swath of moderate EF1 damage early in the day. Although the initial tornado was brief, the low-level mesocyclone persisted for hours and even strengthened to the point it was causing damage as it passed through the city. Tornado warnings were issued due to the TOR signature on radar, but the overall circulation remained broad and weak.

By my understanding it was simply a strong low-level mesocyclone which happened to produce wind damage at times on it's right flank. The full meso was probably 3 miles wide. The survey crew did the correct thing and classified the damage as non-tornadic (though the damage approached EF1 in spots - roughly 85 mph). Of course everyone in the public was confused as to why it wasn't classified as a tornado when there was a tornado warning. It was also frustrating for the NWS staff as it added to their "false alarm" stats.
 
You cannot be scientifically precise for a fluid object that cannot be defined. Nature doesn't care how we classify a tornado versus waterspout versus dust devil.
 
rdale said:
You cannot be scientifically precise for a fluid object that cannot be defined. Nature doesn't care how we classify a tornado versus waterspout versus dust devil.
Click to expand...

While I agree with the overall attitude of the post, I totally disagree that you cannot set a definition. Yes, atmospheric phenomena occur on a continuum of spatiotemporal scales, so the difference between a vortex of width 100 m and 200 m is generally not important, for example, but that doesn't mean you can't set a width threshold for defining one of these vortices as a tornado and the other as not-a-tornado.
 
Jeff Duda said:
No, my point is the meaning of "violent" is subjective and arbitrary. According to previous definitions, 65 mph must have been considered "violent" because it was the bottom of the EF0 wind speed range, and if a tornado was classified as a tornado, then even if it was rated EF0 it apparently, by definition, would have had to have had wind speeds of at least 65 mph. But what do you call a similar vertical vortex attached to a cumuliform cloud that produces winds less than 65 mph? Was that not violent? Who says what is "violent" and what isn't?
Click to expand...

Exactly, an EF0 is still a violently rotating, chaotic column of air, compared to a gentle breeze. It could be capable of putting a piece of debris into an eyeball causing massive damage. So, I guess we will wait for that to happen and someone will sue to put violent back into the definition field. People need to justify their existence. 50 years from now, he can tell his grandchild, "Yep sunny boy, I'm the guy who took the world violent out of the tornado glossary. All under your pappy's leadership."

Lol You just can't make this stuff up

Sent from my iPhone using Stormtrack
 
Last edited:
Brian - what in the world are you talking about? How many EF0 tornadoes have thrown debris into a kid's eyeball? Why is the kid in a tornado in the first place?
 
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