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

Discussion in 'Introductory weather & chasing' started by hazelmaryjackson, Mar 21, 2012.

  1. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    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?
     
  2. rdale

    rdale Member

    Joined:
    Mar 1, 2004
    Messages:
    6,566
    Likes Received:
    233
    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.
     
  3. Bob Hartig

    Bob Hartig Member

    Joined:
    Jul 2, 2004
    Messages:
    1,769
    Likes Received:
    82
    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.
     
    #3 Bob Hartig, Mar 21, 2012
    Last edited by a moderator: Mar 21, 2012
  4. John Vandehei

    Joined:
    Jun 28, 2009
    Messages:
    111
    Likes Received:
    0
    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.
     
  5. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    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.
     
  6. Timothy Finn

    Joined:
    Feb 26, 2012
    Messages:
    88
    Likes Received:
    0
    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
     
  7. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    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.
     
  8. rdale

    rdale Member

    Joined:
    Mar 1, 2004
    Messages:
    6,566
    Likes Received:
    233
    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.
     
  9. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    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.
     
  10. Tim Vasquez

    Tim Vasquez Member

    Joined:
    Dec 4, 2003
    Messages:
    3,411
    Likes Received:
    14
    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
     
  11. rdale

    rdale Member

    Joined:
    Mar 1, 2004
    Messages:
    6,566
    Likes Received:
    233
    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.
     
  12. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    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
     
  13. rdale

    rdale Member

    Joined:
    Mar 1, 2004
    Messages:
    6,566
    Likes Received:
    233
    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.
     
  14. Michael Thomas

    Joined:
    Apr 28, 2011
    Messages:
    21
    Likes Received:
    0
    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.
     
  15. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    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.
     
  16. Bob Hartig

    Bob Hartig Member

    Joined:
    Jul 2, 2004
    Messages:
    1,769
    Likes Received:
    82
    On May 31, 1998, a derecho with winds up to 130 mph blew through Grand Rapids, MI, at around 5 a.m. I remember it well, though my part of town didn't catch the worst of it. I recall a few preliminary flashes of bright lightning, and then suddenly the storm was there, just like that, with crazy lightning and mega-winds. Where my mother lives on the north end of town, near where the peak winds went through, massive cottonwood trees were snapped off and many other large and less brittle trees were debranched and uprooted. In North Park, across the river, a cinder block building had its roof torn off and one of its walls ripped out. The damage in that area was equated to that of an F-2 tornado.

    People living there and nearby were awakened by a sudden, terrifying, jet-like roar, and then came the wind. Naturally they thought that a tornado was upon them, but that wasn't the case. Might as well have been one, though, from the standpoint of the damage.

    My point is, there is no distinctive quality of roar that can always and only be attributed to a tornado. Lots of things can influence the volume and tonal attributes of wind noise, so I wouldn't get caught up in trying to figure out what is what. If a tornado--that is, a vortex connected to both the cloud-base and the ground--is present, then the wind roar you're hearing is a tornado roar; if not, then you're hearing some other kind of a wind roar. Beyond that, you can speculate, but unless and until the matter has been thoroughly and objectively researched, speculation is all it is.
     
    #16 Bob Hartig, Mar 24, 2012
    Last edited by a moderator: Mar 24, 2012
  17. Kelton Halbert

    Joined:
    Jul 6, 2011
    Messages:
    90
    Likes Received:
    61
    I think that this is the most important point that everyone is trying to get across.

    Yes, tornadoes CAN have distinctive roars. NO, they are NOT unique to tornadoes. As stated, there are other processes that can mimic the same sound that everyone talks about. I have not personally experienced this roar, so I cannot speak for myself, but if my understanding is correct, any number of variations in funneling, friction, and wind height/speed can alter the noise the wind makes. Therefore, the sound the wind makes becomes a very poor, subjective and nearly useless tornado detector compared to other methods like a damage assessment by an expert. Yes, even if the wind is compared to something as unique and distinct as a jet engine. It just isn't a good way to detect tornadoes.

    Put it this way:
    I know people have discussed how seismographs have shown activity as large tornadoes approach. Theorize - can this be used to exclusively detect large tornadoes in the proximity of a seismometer? Absolutely not. Why? What if a heavy wind event happens and rattles the building for 5-10 minutes, knocks down several trees, and crushes a nearby building? This would all register on a sensitive seismometer, right? (I've been a room with one and stomped and it registered). Therefore, could it solely detect tornadoes? No. This is a different subject, but the same thought process goes into determining if sound can be used to detect tornadoes. Hopefully this makes some sense?

    This is not to say that a tornado was or was not produced in this particular incident - only to join in the stressing of the fact that such a subjective detector has many flaws.
     
    #17 Kelton Halbert, Mar 24, 2012
    Last edited by a moderator: Mar 24, 2012
  18. Paul Knightley

    Joined:
    Feb 6, 2006
    Messages:
    811
    Likes Received:
    66
    Much of the roar of any windstorm must be attributed to the wind blowing around things, such as trees. In completely clear air, it's hard to explain how wind can make much noise. Perhaps the air accelerating into the low pressure can generate some kind of noise.

    I've heard a distinctive roar aloft when close to a supercell's mesocyclone, which has been attributed by many chasers/meteorologists as being due to hailstones 'bouncing' around (for want of a better term!) in the violent motions aloft.
     
  19. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    I am interested that the senior forecaster at the BOM in Oz said that the Townsville incident could not be classified as a tornado becuse there was no evidence of a funnel. An old friend came round yesterday, (former Chief Surveyor at BP, he was based in Houston for several years and has been all over the world including spending time in Oklahoma). He brought with him a book from his library which he lent me called "Those Terrible Twisters - and the weather of Oklahoma" by Gary England. I expect some of you are familiar with it. Gary was Chief Meteorologist at KWTV for 15 years and a well known consultant meteorologist at the time he wrote it.

    On P32 Gary writes: "The funnel cloud which many people think they must observe for a tornado to exist, forms and becomes visible only when the air flowing into the vortexexperiences a specific pressure decrease and subsequently expands and cools, allowing for tiny water droplets to form. This condensation process, from water vapor to liquid cloud droplets is dependent in each case, on not only the pressure drop but the temperature and moisture content of the air. The warmer and drier the air, the larger the pressure must be for condensation to occur, and as a result it takes longer for the visible funnel to appea. It is therefore quite easy to understand that on many occasions, when the air is quite warm and somewhat dry, the first sight of a tornado on the ground is the sight of debris and dust erupting skyward."

    He goes on to cite as an example of the unpredictablity of tornadoes, a small tornado which touched down near Elk City, OK, causing significant damage, on 29 april 1984, before any radar ever detected a thunderstorm in progress. I know great strides have been made in prediction since then, but it alls does show that a tornado can form on the ground before a funnel is apparent .
     
  20. rdale

    rdale Member

    Joined:
    Mar 1, 2004
    Messages:
    6,566
    Likes Received:
    233
    You probably misunderstood him. He means there was no evidence based on the damage that a tornado occurred.
     
  21. Tim Shriver

    Joined:
    Apr 10, 2008
    Messages:
    387
    Likes Received:
    1
    First, I have seen very few true funnels become tornadoes, if any.

    Most of the time the rotation on the ground is occuring before you see the condensation funnel form. Westfield WI F5 is a good
    example.

    Unless you are able to see the rotation on the ground it is a funnel.

    The condisation funnel you see in a tornado is in the center of the tornado and not the outside of the 'nado.

    Remember, you can not see air until it picks up something you can see.

    Also, even though everyone and their dog says it, it is wrong 99 percent of the time. Tornadoes do not play football thus
    they do not "touch down". They spin up.

    Tim
     
  22. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    From TVNZ (and others)

    Australian Bureau of Meteorologist senior forecaster Brett Harrison said ...................................... the bureau was not describing it as a tornado as there were no reports of a funnel."
     
  23. rdale

    rdale Member

    Joined:
    Mar 1, 2004
    Messages:
    6,566
    Likes Received:
    233
    So no reports of funnel and no evidence of a tornado in the damage... I think we already went down this road ;)

    Without that, it's not going to be called a tornado. I'm not sure why there is still confusion?
     
  24. Michael Thomas

    Joined:
    Apr 28, 2011
    Messages:
    21
    Likes Received:
    0
    From what I understand, there is/was very strong evidence of a tornado in the damage. I also thought the BoM had confirmed there was a tornado. While it is true that no-one has reported seeing a funnel, keep in mind it was dark at the time (very early morning) and if there was a tornado, it was likely embedded in rain (see my previous post). This storm was very close to home for me (though I haven't been home for ages). Luckily my place was fine, though a few palm fronds were torn from the palm outside my place.

    Interestingly, it also appears there was a tornado in the suburbs of Sydney on the 8th of April, 2012. Initial, unofficial reports have a path length of around 9 km with ~F0/F1 damage (mostly in National Park fortunately). Unfortunately, this occurred in the evening and again there are no reports of a funnel being sighted.

    This reminds with of "If a tree falls in the forest and no one is around to hear it does it make a sound?"
     
    #24 Michael Thomas, Apr 12, 2012
    Last edited by a moderator: Apr 12, 2012
  25. hazelmaryjackson

    Joined:
    May 24, 2011
    Messages:
    58
    Likes Received:
    0
    As a matter of fact I don't think there has been any "official" announcement of whether the Townsville "severe weather incident" was a tornado or straight line winds. From what I have read, the "experts" disagree and no formal report has et been issued by the BOM. This update (below) appeared in the Townsville Bulletin in the aftermath on 21st March.

    "Bureau of Meteorology severe weather forecaster David Grant said the short-lived storm was a supercell from a thunderstorm that had moved across Townsville just after 5am. "We can't confirm or deny whether it was a tornado, but going by the damage reports, it's every possibility that it's true," he said.

    The damaging winds were caused by the southward movement of a low-pressure trough across Townsville from the North. It struck at 5.07am at Townsville Airport, bringing with it 148mm of rainfall in the 24 hours up to 9am yesterday.

    Weatherzone chief meteorologist Alex Zadnik said easterly winds had converged with stronger winds from the north to create the storm. The convergence of winds led to one of the conditions needed for thunderstorm development and may have created the ingredient for the tornado to form, he said.

    "It isn't completely clear whether the damage around the suburb of Vincent was the result of a tornado or simply violent winds that can accompany the movement of a trough and thunderstorm activity through a region," Mr Zadnik said. "However, it is worth highlighting there can be tornadoes in Australia, so there is no need to describe them as mini if they do occur."

    Mr Zadnik said based on photographs of the destruction caused by the storm, it could be graded as an EF1 level tornado, with wind speeds ranging between 138km/h-178km/h. An EF5 level tornado, in comparison, has wind speeds of more than 322km/h.

    Dr David Henderson from James Cook University's Cyclone Testing Station was trawling Vincent streets yesterday trying to ascertain the storm's severity. "The debris is on a couple of different angles, so that may suggest things like a mini-tornado," he said."

    Anyone know if BOM has issued an official classification yet?
     

Share This Page