Mini-Tornadoes: Defining a Microscale Mystery

In Europe they have mini-tornadoes. There was a time in my callow, formative years as a storm chaser when I was unaware that there was such a thing, but one learns. Besides, even veteran American chasers could make the same mistake as I, and probably have done so many times. From the reports, photos, and videos I've seen, a mini-tornado so closely resembles a standard-issue tornado in appearance and effect that here in the United States, most chasers would find it impossible to tell the difference. However, Europeans--newscasters and reporters in particular, who are largely responsible for disseminating the mini-terminology--are more discriminating and not easily impressed. In Europe, it seems that anything less than a Great Plains-style wedge isn't considered a full-fledged tornado. Not that wedges are a common occurrence across the pond. The perspective I've described appears to be based not on great familiarity with tornadoes, but rather, on a paucity of experience with them other than what is gleaned through viewing videos of the mile-wide monsters that stalk the American prairies. Now those are tornadoes! Compared to them, a trifling, block-wide vortex is ... eh. Small change. Plenty of U.S. chasers would take exception. The problem is, no mini-tornado criteria have been established that could provide a basis for arguing that probably 99.9 percent of mini-tornadoes are simply tornadoes. Not that at least one attempt hasn't been made to provide such criteria. Back in 2006, in a thread on Stormtrack, I myself presented a plausible set of determinants for mini-tornadoes, complete with a damage-rating scale, and I'm surprised that the NWS never adopted it. Follow my logic and you'll see for yourself that true mini-tornadoes are a phenomenon few Europeans, let alone Americans, ever encounter. Mini-Tornado Criteria A true mini-tornado must meet the following standards: . •  It is five feet tall or less. Of course, this implies an extremely low cloud base. You'd have to squat in order to get a decent photo. •  Width: Two feet or less. •  Human response: You feel a strong urge to say, "Awww, ain't that cute!" You want to pet it and maybe even take it home with you and give it a nice bowl of debris. •  The synoptic conditions can be contained within five city blocks. •  Overshooting tops can be viewed from above by taking an elevator to the ninth floor. •  Damage (introducing the M Scale):
  • M0: Damage?
  • M1: No noticeable damage.
  • M2: No, there's no stinking damage. Now go away.
  • M3: Okay, some damage now. Card houses knocked over unless securely glued together. Hair ruffled. That sort of thing.
  • M4: Now we're talking damage. Well-built card houses scattered into a lawn-size version of 52-Card Pickup. Ill-fitting toupes snatched away. Nasty things happen when you spit into the wind.
  • M5: Inconceivable inconvenience. Securely glued card houses swept entirely away and lofted across the lawn. Well-gelled hair twisted into impressive new designs. You want to get out of the way of this baby.
I hope this helps. Of course, according to these criteria, I suppose the UK has yet to experience a true mini-tornado. Someone should probably inform the press. And none of us should hold our breaths waiting for such an occurrence, because, truth be told, mini-tornadoes are extremely rare. But not utterly non-existent. The late, talented storm chaser Andy Gabrielson managed to capture on video his personal encounter with a good mini-tornado candidate on May 24, 2010, in South Dakota.* Check out his YouTube video at 1:56, and like me, you too can say to yourself, "What the heck was that?" --------------- * The footage up to 1:56 is not a mini-tornado.
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  1. The mini-tornado in this video made me think of a dust devil, in terms of height, width, and intensity (or pseudo-intensity, if you’d prefer that term). Wonder if it’s just a type of devil that forms only with thunderstorms. The time I saw a dust a devil, it came up to my car, and the experience was a bit like what is seen in the video, only it didn’t even slightly shake the car or make any noise. Maybe dust devils should have a DD scale.

    P.S. Strong, violent, and maxie tornadoes have formed in Europe, probably just a bigger deal when they do, I suppose. I wish more data was available on them.

  2. Thanks for your comment, John. The point of my article was to poke fun at the nomenclature. It seems that the term “mini-tornado” is used widely in Europe for vortices that Americans chasers and meteorologists would simply call tornadoes. If a vortex on the ground connects with the cloud base, then it’s a tornado, regardless of how big or small it is.

    On a related note, size has nothing to do with tornado intensity. There may be an overall correlation, but some very small tornadoes have been violent enough to do EF5 damage; the June 22, 2007, tornado that occurred in Elie, Manitoba, Canada comes to mind. Conversely, some very large tornadoes may be less powerful than their size suggests–or every bit as powerful. It varies from storm to storm, depending on conditions.

    As for that little guy in the video, while I can’t say for sure, I strongly suspect it was a bona-fide tornado. The conditions it occurred in weren’t right for dust devils, but they were obviously prime for tornadoes. Moreover, a dust devil doesn’t produce a condensation cloud, whereas this vortex is all condensation and is intense for its size. Problem is, there’s a lot that the video doesn’t show. We only see the lowest few feet where rotation is interacting with the ground. What was going on up above? There’s no way of knowing, but it’s a reasonable bet that there was circulation at the cloud base and possibly a condensation funnel extending downward.

  3. I did enjoy the M-scale joke, and thanks for clearing some of my confusion up. So, a “devil” doesn’t connect with the cloud? is that the main criteria for it? And how powerful can tornadoes in Europe get? Have they ever had an F/EF4 or F/EF5?

    P.S. Inconceivable inconvenience? I shudder to think…imagine how awful M6 would be!

  4. A dust devil is actually a fair-weather phenomenon. It typically occurs on sunny days and is a product of localized surface heating beneath cooler air, which can produce a rotating updraft. While some dust devils can get large and relatively strong, most are harmless, though they may look impressive. I remember driving through Arizona with my family when I was a teenager and seeing scores of dust devils parading slowly across the desert, some reaching over 1,000 into the bright blue afternoon sky. Very cool to see!

    There is absolutely no difference between European tornadoes and U.S. tornadoes. A tornado is a tornado. The U.S. is known for the frequency, number, and violence of its tornadoes, but this is simply because our geography creates ideal conditions for them.

    A number of European and Eastern countries have had violent tornadoes. On June 9, 1984, a Russian outbreak north of Moscow produced a number of deadly tornadoes, including one F4 and one F5. Here is the Wikipedia article. Italy recently experienced a dramatic tornado in the town of Taranto, where this spectacular video was shot. Poland has had a number of impressive tornadoes in recent years, and France has been visited by at least one F4 tornado. You may take an interest in this Wiki on European tornadoes and tornado outbreaks.

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