Can it be a tornado if there isn't a funnel?

[hazelmaryjackson]

A interesting incident occurred recently in Australia, where local residents reported that the storm cell over their town had given rise to a particuarly damaging bout of wind which appeared, according to local residents, to have many of the characteristics of a tornado ("green" lighting, a roar like a jet engine, power flashes etc and winds damaging enough to rip the roofs and one level off a number of buildings and bring down power lines.) However the senior forecaster at the ABM said it could not be classified as a tornado as there were no reports of a funnel. I gather that how to define this particular storm has generated a lot of debate among storm chasers in Oz. So, does a tornado always have a funnel? Can it be a tornado without a funnel?

 

[rdale]

None of those characteristics are related to tornado. Green lightning means nothing, a roar means strong winds, power flashes means strong winds, and roofs off means strong winds. Seeing a funnel doesn't matter either.

But 1) if nobody saw a funnel and 2) the damage doesn't indicate tornado then 3) it was not a tornado.

 

[Bob Hartig]

Yes, you can have a tornado without a funnel cloud. Tornadoes are defined as a vortex that connects with both the ground and cloud base; the funnel is just a feature of that vortex, and it may not always be present. Moreover, it's not always easy to discern between a funnel cloud (rotation aloft but not impacting the ground) and a tornado. Often what appears to be just a funnel cloud is in fact a tornado; the determining factor lies in what's happening on the ground.

This quote from NOAA's tornado FAQ offers plenty of information:

According to the Glossary of Meteorology (AMS 2000), a tornado is "a violently rotating column of air, pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud." Literally, in order for a vortex to be classified as a tornado, it must be in contact with the ground and the cloud base. Weather scientists haven't found it so simple in practice, however, to classify and define tornadoes. For example, the difference is unclear between an strong mesocyclone (parent thunderstorm circulation) on the ground, and a large, weak tornado. There is also disagreement as to whether separate touchdowns of the same funnel constitute separate tornadoes. It is well-known that a tornado may not have a visible funnel. Also, at what wind speed of the cloud-to-ground vortex does a tornado begin? How close must two or more different tornadic circulations become to qualify as a one multiple-vortex tornado, instead of separate tornadoes? There are no firm answers.

Green lightning, a jet-like roar, power flashes, and roofs ripped off do not necessarily mean that a tornado was the culprit. A violent thunderstorm with strong straight-line winds can produce all of those effects. The key is whether there was tornadic rotation, something that can be determined by expert damage assessment--the operative word being "expert." After such an event, people typically insist that a tornado had to have been involved and will cite how branches got "twisted" off of trees and so forth. But what counts is whether the broad-scale damage path shows a circulating pattern.

 

[John Vandehei]

I can tell you from personal experience that there can be a tornado without an visible funnel. I was chasing a tornado warned storm in the Battle Creek, MI area several years back. I got slowed up by city traffic attempting to stay ahead of the storm and eventually got caught in the rain core. While attempting to move east on I-94 to try and get back ahead of the storm (I was still trapped in the rain), I noticed numerous leaves in the air about a block ahead of me. They were swirling around rapidly in a circle of vultures pattern. I immediately through "tornado", but then discounted it when I saw all the traffic driving right through the circulation unaffected. So I continued on, through the circulation. Although my vehicle bucked in the wind, no harm was done. I later learned that a confirmed tornado passed through that location. The thing was, I never saw a funnel, wall cloud or anything except those leaves. Though it was raining, visibility was about a quarter mile. All this being said, I can't tell you what actually happened with the storm you are referring to.

 

[hazelmaryjackson]

Well I saw several tornadoes when I was out chasing in the Mid West last year, but the only time I have ever been underneath one, was few years ago, in London, when one passed overhead, but I did not know this until later. Basically the sky got dark, a strange greenish clour, and then it briefly hailed, and then the rain started. Tornadoes are rare to vanishing point in London, especially in November, so I just thought it was a passing storm cell. True the rain was being blown along by the wind, but again I just assumed that was the wind. What I did notice was the roar overhead, I thought it was a jet landing at Heathrow nearby and was surprised it had been given clearance in such a bad thunderstorm. A few minutes later a tornado (later verified as such) touched down about 5 miles directly north west of me (and I later found I was under its path at the time I heard the roar). I never saw a funnel when I looked out of the window at the storm and it only touched down for a couple of minutes so there are no photos of a funnel but it was confirmed as a tornado. The local eye witness accounts were very similar to those which were reported by the Australian residents.

 

[Timothy Finn]

I was taught that as long as you have rotation above, and can ascertain a vortex at the ground, normally via a debris cloud, then you have a tornado. A condensation funnel isn't a requirement for a tornado, by definition.

Tim

 

[hazelmaryjackson]

The thing that struck me about the residents' comments most was their description of the roar overhead like a jet engine. That is exactly what I mistook the London tornado for when it passed overhead. I have been in severe storms and in desert regions where the wind howls, and it is not at all the same sound as the roar of a tornado.

 

[rdale]

Strong winds sound like a jet engine, which is why I said it holds no meaning when it comes to determining a tornado. As you mentioned, you heard it but there was no tornado occurring at that time.

 

[hazelmaryjackson]

Strong winds sound like a jet engine, which is why I said it holds no meaning when it comes to determining a tornado. As you mentioned, you heard it but there was no tornado occurring at that time.

There was a tornado forming above me, when I heard the jet engine sound, and it WAS a tornado - that has been verified. At the time it would have been rain wrapped and descending as it touched down only a few minutes later. Are you saying it does not roar until it is actually on the ground? It sounded like a jet engine. I have been in a lot of high winds, and they did not sound like that and in 1986 we had a hurricane in London which created severe damage including uprooting trees and it did not sound like a jet engine roar. Still it would be interesting to know at what point in its life cycle a tornado starts roaring and if the sound is in fact identical to strong winds.

 

[Tim Vasquez]

Overall RDale, Bob, and others summed it up nicely. Here in Oklahoma we do see a lot of the "green lightning", power flashes, roars, downed lines, ripped roofs, etc, where the radar network indicates pretty conclusively that we were dealing with outflow. However, your question does bring up a few uncertainties:

* Definitions: What is a tornado? Bob gave us some definitions above, and the AMS Glossary gives the de-facto definition, but many scientists might offer different opinions on the details. Chuck Doswell addresses this quite nicely here. Here in the US, we don't like to call it a tornado unless there is a parent mesocyclone, and that requires some radar data or well-documented field observations to back it up.

* Absolutes: We can't say with absolute certainty that it wasn't rotational, as vortices can occur through a whole spectrum of temporal and spatial scales. The gustnado has been pretty well documented; they're very transitory and you can find video of that on YouTube, and there is emerging research dealing with leading edge vortices -- I'm drawing blanks on a good reference, but I'd start with Przybylinski 1995 here; it's pretty technical but if you hunt around in it, there's some understandable info that talks about these vortices. Are those tornadoes? Again we have to go back to definitions.

Obviously we're going down a rabbit hole, but given that there was no field data (and presumably no Australian radar data.. does anyone archive their live stuff?) and eyewitness data from public sources is pretty unreliable, and that those facts only suggest some type of wind, I would predicate this on what the Australian forecaster says. He/she had access to the soundings and maybe some of the radar data and would be best qualified to give the answer. They're probably saying, at least, that it wasn't associated with a mesocyclone, and that the environment wasn't conducive to this type of storm. So I'd lean toward it being outflow damage. That's not to say there wasn't a gustnado or small-scale vortex involved, and we don't know how the Australian forecaster arrived at their conclusion, but I'd go with outflow on this one.

Tim

 

[rdale]

There was a tornado forming above me

I think we're getting into semantics But it is not a tornado until there is something also occurring on the ground. You heard the winds overhead, nothing more and nothing less. You did not hear a tornado overhead, because there was no tornado overhead.

 

[hazelmaryjackson]

I think we're getting into semantics But it is not a tornado until there is something also occurring on the ground. You heard the winds overhead, nothing more and nothing less. You did not hear a tornado overhead, because there was no tornado overhead.

OK let us say there was a funnel overhead of me not a tornado - as when I spent 15 minutes last year watching a funnel form and reform before it eventually dropped - at what stage can you hear the distinctive roaring? Is it at the funnel stage or only when it touches down - see http://www.stormtrack.org/archive/0263.htm for an interesting discussion about this?























http://www.stormtrack.org/archive/0263.htm

 

[rdale]

Roaring in the clouds is usually associated with a strong mesocyclone. It's not really a "stage" of tornado development. It can happen without a tornado ever occurring.

 

[Michael Thomas]

Going back to the possible tornado in Australia, I assume we are talking about the event in Townsville on the 20/3/12 at around 5 am local time. From my general take on things, it seems that most storm chasers/weather enthusiasts are in agreement that this was a tornado.

Radar-
http://www.theweatherchaser.com/rad...ille-hervey-range/2012-03-19-12/2012-03-20-12

Morning sounding (at location of possible tornado, 4 hours after the event)-
http://soundings.bsch.au.com/skew-t...03&day=20&year=2012&hour=00&window=on&hodo=on

Surface observations-
http://www.bom.gov.au/products/IDQ60801/IDQ60801.94294.shtml

The fact that no funnel was sighted is not suprising since it was still dark at the time. Also, if there was a tornado, it was likely hidden by rain and cloud bases were also very low. When looking at the morning sounding, note that surface winds were E'ly prior to the possible tornado which would have increased low-level shear. The morning sounding shows plenty of low-level CAPE which I believe is also an important factor in tornadogenesis.

 

[hazelmaryjackson]

The point Ihave been trying to make about the roar, not very successfully, is that I grew up around planes and currently I live under the Heathrow flight path. I have lived and travelled in parts of the world where there are strong storms and winds, and last year I was out chasing in the midwest. So I know what wind sounds like and I know what jets sound like. When a big jet comes in to land there is more than just a roar there is a very distinctive sort of whine about the engines which is different from wind. That is why, when the massive thunderstorm (as I thought) went over London I took on board the screaming winds and torrential rain and the hail (the winds seemed to be blowing the rain sideways ) but then over and above all that I heard what sounded to me exactly like the distinctive whine of a big jet coming in to lan.d I was more than surprised that it should be allowed to land in such a massive thunderstorm. But of course it turned out that there was no jet, a few minutes later a tornado touched down just north west of me and we were right under the path of the supercell storm which generated it. I did not see any funnel cloud out of my windows but it would in any case have been rain wrapped.

To me strong winds do not sound like a jet whine, which I hear multiple times a day coming in to land. We will have to agree to differ on that although it does raise interesting questions of when and why a tornado roars.

Regarding Townsville, the senior forecaster at the Australian BoM, Brett Harrison, said the weather event which hit Townsville could not be be called a tornado because it did not have a funnel. For the BoM in Australia to be classified as a tornado it has to have a funnel. I have some Oz storm chaser friends and I understand a fierce debate has been going on over whether it was a tornado or straight line winds. My friends favour the straight line winds option. I await the result of official investigations with interest. Particularly if it does seem to have been a tornado, to see how they square the circle at the BoM.