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

[Bob Hartig]

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.

 

[Kelton Halbert]

My point is, there is no distinctive quality of roar that can always and only be attributed to a tornado.

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.

 

[Paul Knightley]

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.

 

[hazelmaryjackson]

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 .

 

[rdale]

You probably misunderstood him. He means there was no evidence based on the damage that a tornado occurred.

 

[Tim Shriver]

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

 

[hazelmaryjackson]

You probably misunderstood him. He means there was no evidence based on the damage that a tornado occurred.

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."

 

[rdale]

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?

 

[Michael Thomas]

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?"

 

[hazelmaryjackson]

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?

 

[rdale]

I've never heard a "mini-tornado" classified in the literature, so I'd use caution with any research using that term.

 

[Michael Thomas]

Rdale, welcome to Australia. Very frustrating at times seeing what is reported.

As far as damage is concerned. I think these guys (OzCyclone chasers) have done a good job, clearly the damage is not consistent with straight-line winds-
http://www.youtube.com/watch?v=vm1F-L5t8Nk
http://www.youtube.com/watch?v=6ItfViY2ytA

This video shows some more damage further along the damage path-
http://www.youtube.com/watch?v=ZQJNg6y1jks&feature=related

 

[joel ewing]

Don't forget hail roar in the clouds, too.

 

[Steven Williams]

I've never heard a "mini-tornado" classified in the literature, so I'd use caution with any research using that term.

The term "mini-tornado" is a media term which I think originates from Britian and has been used by the Australian and New Zealand media. The EF scale is not recognised over here and the tornadoes are short lived and often weak.

 

[Paul Knightley]

Yes, sadly 'mini-tornado' is, I think, a term which was coined over here. For a number of years no-one seemed to correct people but I, and several others, have been doing our level best in the last 10 years! The term does seem to be becoming less used now, which is great!