Tornado Or Not?

[rdale]

The first time one of these cold-air funnels flips a school bus over is the last time they don't get warned for.

I can't imagine a way that a EF0 anything could flip over an occcupied school bus... And if a bus driver actually drove into a funnnel, I think there's more issues to debate

 

[Tim Shriver]

I did witness cars being picked up and placed on top of others, flipped over etc., in I think it was 1987 or 1988, at a Toyota dealership in Madison WI. This damage was caused by what the NWS named a cold air funnel. These cars were not as big and heavy
as a school bus, but still it was impressive.

I was working down the road at the Ford dealership.

For the most part they are harmless, but every now and then they can surprise you.


Tim

 

[Dann Cianca]

Got a response from the Missoula NWS:

These funnels are considered "cold air" funnels associated with cold
unstable atmosphere in place but not occurring with severe
thunderstorms. If these funnels touch the ground, they are called land
spouts. They can cause damage if wind speeds
reach up to around 60 mph. But usually they don't have winds speeds
that strong. Tornadoes are only associated with severe thunderstorms,
and there were no thunderstorms occurring during this time frame.

Thank you for your interest, and please contact us again if you have
further questions or comments.

Crystal Lake
NWS Missoula

 

[rdale]

I've never heard that explanation... I wonder where that came from?

 

[Dann Cianca]

I've never heard that explanation... I wonder where that came from?

I know ... and this bit blew me away:

Tornadoes are only associated with severe thunderstorms

... ???

 

[Scott McLaughlin]

I have the agree also that this is a tornado.It is no longer a funnel due to the fact that it is on the ground. This to me is a Tornado!!!

 

[Damon Poole]

The difference between cold air funnels and tornadoes is that tornadoes are pendant from mesocyclones within severe thunderstorms, which is stated in both the Weather Service e-mail, and in the Basic Spotters Guide. By NWS Definition, a tornado is a violently rotating column of air extending from the base of a thunderstorm to the ground. If the column is not in contact with the ground, it is technically a funnel cloud.

Cold air funnels are formed from cumuliform clouds, but these are not associated with the mesocyclone in severe thunderstorms. That's the difference.

 

[Darin Brunin]

If one calls this a tornado, then every single landspout, gustnado, waterspout etc. in history, had better also be grouped into a single category known as "tornado". While it is a cool phenomenon, they are formed from two different convective processes and it would be a shame to see it labeled a simple "tornado"...especially for scientific purposes, as there needs to be a clear distinction between the two. Landspout tornado maybe but simply calling it a tornado is wrong.

A supercell produced tornado over water is still a classic tornado and not a waterspout.

A waterspout over land is still a waterspout because it only formed because of a body of water and then moved onto shore. Just because it has ground circulation, doesn't earn it the distinction of being labeled the same kind of tornado that forms from a supercell thunderstorm.

The general public calling this a tornado would be acceptable but we as storm chasers should know better and I hope that nobody on this forum would call this in as a "tornado" without clarifying.

 

[rdale]

By NWS Definition, a tornado is a violently rotating column of air extending from the base of a thunderstorm to the ground.

That's incorrect... Here is the accepted definition of a tornado:

"A violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud."

http://amsglossary.allenpress.com/glossary/search?id=tornado1

The informal NWS version, "A violently rotating column of air, usually pendant to a cumulonimbus, with circulation reaching the ground" makes no mention of a thunderstorm either.

http://www.weather.gov/glossary/index.php?word=tornado

Clearly it's from a cumuliform cloud (as you pointed out in your post.) No mention of supercell, let alone thunderstorm, in the definitions. (I would HOPE people don't think that any non-supercell tornado is not a tornado???)

Regardless, per official definition, it's clearly a tornado.

http://www.cimms.ou.edu/~doswell/a_tornado/atornado.html

Landspout tornado maybe

I totally agree... Add the class, but don't deny it's a tornado. If that thing moved through my viewing area, but I didn't interrupt programming because "it's not a tornado" I'd get fired and the local NWS MIC would be on tomorrow's front page saying "IT'S NOT A TORNADO"

 

[Scott Weberpal]

The general public calling this a tornado would be acceptable but we as storm chasers should know better and I hope that nobody on this forum would call this in as a "tornado" without clarifying.

Save the clarifying until after the fact. If I see a landspout, it's getting called in as a tornado. The reason for a tornado warning is to protect lives, and if a NWS office refuses to issue a tornado warning because it's a non-supercell tornado (yes, another name for a landspout which includes the name tornado), I'm going to tell them it's a tornado and leave out the non-supercell part. Supercell and non-supercell tornadoes, IMO, should be classified as one in the same. Though they are both produced by different processes, non-supercell tornadoes are just as apt to produce significant damage. If someone in the NCDC database wants to keep them separate, that's fine, but for warning and public information purposes there should be no distinction between the two. Landspout is the generic term anyway, more and more in the weather world are using "non-supercell tornado". As far as I'm concerned, both are violently rotating columns of air in contact with the ground extending from cumuliform clouds...gustnadoes can't be grouped with them as they are a product of winds at the surface and are not attached to a cumuliform cloud.

 

[Darin Brunin]

NWS Lubbock seems to think there needs to be a clarification of the two.
http://www.spc.noaa.gov/climo/reports/070325_rpts.html

Dust devils rotate and cause damage...should tornado warnings be issued for them as well? They can cause a threat to life or property and I am sure some dust devils are just as strong as some landspouts. Heck....I bet that a lot of dust devils are on the ground longer than quite a few landspouts.

If NWS offices issued tornado warnings every time that there's a landspout report called in it's easily going to lower people's perception of danger when there is actually a needed tornado warning and could ultimately lead to more lives being lost when people don't take warnings seriously because so many unneeded warnings are being issued. Now, if there is a known landspout that's doing signifcant damage that could be another story but to say more than 10%(if that) of landspouts are capable of doing significant damage is something that would definitely lead to a false sense of warning IMO.

 

[Tim Shriver]

I don't think anyone is saying that the NWS should sound the alarm each
time a CAF is spotted, nor do I think they should ignore them.

If a dust devil is doing damage to property and threatening lives, yes, sound the
alarm. Otherwise let it live in peace.
Same with a CAF.

As with any weather event or enemy, the true measure is its individual displayed potential to do harm.
Each observed and judged on its own.

Tim

 

[rdale]

Dust devils rotate and cause damage...should tornado warnings be issued for them as well?

DD's are not connected to a cumuliform cloud, so the easy answer there (at least fitting the definition of a tornado) would be no.

If NWS offices issued tornado warnings every time that there's a landspout report called in it's easily going to lower people's perception of danger when there is actually a needed tornado warning

If the above pictured "whirl" is going through a city and the sirens are sounding - I'm not sure how you can say that would lower the perception of tornado warnings. Most warnings are false alarms (some offices in Tornado Alley are running at 90 (ninety) percent false alarm ratio this year) so I just don't get how alerting people of the pictured event would hurt the future warning process.

 

[Dann Cianca]

I wrote back to the Missoula NWS asking for a bit of clarification and got a response from the SOO...

Dann,

You bring up many good points about tornadoes vs. land spouts vs. cold air funnels. We've been having similar debates here the last few days. It's one of those gray areas that's hard to define. I think specifically by definition any violently rotating column of air that touches the ground could be considered a tornado. Regardless of the formation process. Rarely do land spouts produce damage, but like you mention there are a few notable exceptions. Though, even dust devils can produce minor damage.

I think from a forecasting / weather watch standpoint, it's very useful for us to classify phenomena based on formation process so that have expectations of potential development based upon meteorological factors. Really, all vorticies form in the same process...stretching of vorticity. In most cases in the atmosphere, the stretching occurs by enhanced vertical motions of some pre-existing low level shear. With "meso-cyclone" induced tornadoes, you have pre-existing vorticity aloft, and generally very strong updrafts, which can lead to very strong low level circulations. With land spouts and water spouts, there is generally little in-cloud pre-existing vorticity, and it's simply vorticity stretching by a weak to moderate updraft that happened to pass over the region of low level shear. Really cold air funnels and land spouts form by the same processes, except one doesn't touch the ground.

I think the issue for us as an agency trying to issue weather warnings is the message we are trying to send to the public. I think sometimes this works it's way into the terminology and criteria we use to base our warnings on. I think this plays into land spout vs. tornado terminology, in particular the 60 MPH limit. This is basically the definition of severe vs. non severe winds, even though there may be no real scientific basis for the 60 MPH limit. In general, land spouts are short lived and are not particularly hazardous, with a few very notable exceptions, therefore typically non-severe. For most people a tornado means a very damaging / life threatening phenomena. So the terminology and criteria may have grown around the expectation that land spouts are more of a nuisance then anything, even if by strict definition a land spout might be considered a tornado as in a violently rotating column of air. Though, the specific definition of a land spout is: "A form of tornado not associated with a mesocyclone of a thunderstorm that touches the cloud base and the ground".

The other problem for us, is that this is probably the first report of a land spout / funnel in many years that we could actually verify. Even then, we didn't hear about it until at least 40 minutes after it happened. So a warning would have been useless. If there are no indications on radar, or if the weather for the day isn't necessarily conducive to classical tornadoes, when we get these reports, it's either generally too late to issue any type of warning or special weather statement, or we can't verify them and thus don't have the confidence to issue any products.

Hope this helps.

Gene Petrescu
SOO WFO Missoula

I think that answers a lot of the ambiguity.

Thoughts?

 

[rdale]

I like that response better... At no time did I indicate that a tornado warning should be issued, let alone 40 minutes after the fact. But you can't deny (using the current, accepted definition of a tornado) that was a tornado.