Tornado Or Not?

[Dann Cianca]

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.

Yeah, the warning was probably not necessary. I like the idea of a special weather statement if it is current. Chances are (especially in landspout cases) that more than one can form.

I seem to recall a warning or statement issued in Colorado last year or the year before that said something to the effect of "landspout tornadoes expected for the next few hours" At that time, there were five on the ground near Boyero/Wild Horse.

 

[Darin Brunin]

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.

Do you really think I was really being serious about issuing tornado warnings for dust devils lol. I was just comparing the two saying that if landspouts produce damage and are cause for warning...dust devils cause damage as well and was joking that they rotate too.

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.

Like I said....If there is a landspout that's doing significant damage and even more significantly, doing it in a metro area, that's another story but I would imagine that just as soon as a warning was issued for 99% of landspouts...the circulation would no longer be in contact with the ground. It doesn't matter if most warnings are false alarms now....it's only going to drive the point further across to people to dismiss tornado warnings if a landspout with 50mph winds, a total time duration on the ground of 30 seconds, and 30 miles away from civilization gets a tornado warning issued for it because the spotter didn't bother to mention that it was a landspout. And yes....there can be weak supercell tornadoes as well in open country but they or future potential tornadoes from the parent supercell have the potential to be many times stronger than a weak landspout from a popcorn thunderstorm.

 

[Greg McLaughlin]

Have there been any confirmed injuries or deaths related to dust devils in the past?

 

[Brent Gilles]

The picture is clearly a landspout, which by pure definition is a tornado, but because the processes are different the classification is needed for scientific purposes.

I see no issue with issuing a special weather statement stating that a landspout has been spotted and you should take precautions because they can cause damage. Now that the NWS issues storm specific warnings you can't pinpoint a specific storm for a landspout so how do they issue a warning?

Issuing too many warnings is a whole other topic I think.

 

[Jason Harris]

dust devil injuries

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Greg McLaughlin: Have there been any confirmed injuries or deaths related to dust devils in the past?
---


Here's one Greg, from the storm reports from spc.noaa.gov:
2045 UNK ZENIFF NAVAJO AZ 3548 11033 *** 3 INJ *** Dust devil ripped shingles roofs, blew down four large blew over two ticket booths lifted roof off a fixed str Winds estimated at 40 to 50 (FLG)

But apparently later estimates were up to 75 mph on that feisty dust devil:
"dust devil struck the Coconino County Fairgrounds in Flagstaff, Arizona on September 14, 2000. Extensive damage occurred to several temporary tents, stands and booths, as well as some permanent fairgrounds structures. In addition, several injuries were reported, but there were no fatalities. Based on the degree of damage left behind, it is estimated that the dust devil produced winds as high as 75 mph (120 km/h), which is equivalent to a moderate-strength EF0 tornado."

"Wind speeds in larger dust devils can reach 60 mph or greater. Even though they are generally smaller than tornadoes, dust devils can still be destructive as they lift dust and other debris into the air. Small structures can be damaged, and even destroyed, if in the path of a strong dust devil."
http://www.wrh.noaa.gov/fgz/science/dustdvl.php?wfo=fgz


Navajo nation notes "A strong dust devil and ["can" sic] actually pick up a human or small animal." http://www.dnr.navajo.org/Drought/NNDrought2006.htm

 

[Damon Poole]

RDale wrote: "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." -

The above definition may be the "accepted definition of a tornado:" but the definition I gave was the definition published in the Basic Spotter's Field Guide by the National Weather Service. Since the NWS is responsible for issuing official tornado warnings, it is the NWS definition that matters. While the cold air funnel may technically be a tornado when it touches down, that doesn't mean it necessarily meets the agency definition for tornado warning purposes. If there is a discrepency with the GOM, take the matter up with the National Weather Service and see if you can get the training guides changed, but do not call my answer incorrect because I gave a different definition than yours. That is not your place.

Also, RDale wrote: "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." -

That is an incorrect statement - a cumulonimbus is indeed a thunderstorm cloud. See the following GOM definition:

thunderstorm—(Sometimes called electrical storm.) In general, a local storm, invariably produced by a cumulonimbus cloud and always accompanied by lightning and thunder, usually with strong gusts of wind, heavy rain, and sometimes with hail.

Most people use the terms thunderstorm and cumulonimbus interchangeably, thus the informal definition most definitely mentions a thunderstorm.

 

[rdale]

The above definition may be the "accepted accepted definition of a tornado:

Correct, from the AMS, who is the "official" meteorological source.

Basic Spotter's Field Guide by the National Weather Service.

I struggle in accepting that you are using their basic spotter guide as an official source of meteorological definitions.

Since the NWS is responsible for issuing official tornado warnings, it is the NWS definition that matters.

We weren't talking about warnings, we're talking about the above picture. And for that, the AMS definition matters. There's no question it is a tornado

Also, RDale also wrote: "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." -

That is an incorrect statement - a cumulonimbus is indeed a thunderstorm cloud. See the following GOM definition

I posted the official NWS definition, from the official NWS glossary. It makes no mention of REQUIRING a thunderstorm. Note the word "usually." That means there are times that the violently rotating column of air is NOT pendant to a cumulonimbus (thunderstorm) but is still classified as a tornado. If the NWS definition required a thunderstorm, they would have taken the word "usually" out.

 

[Damon Poole]

Originally Posted by rdale
1. Correct, from the AMS, who is the "official" meteorological source.

The GOM is published by the AMS, not the NWS. The AMS does not issue forecasts or weather warnings, the NWS does. I don't question the AMS as a meteorological source, but the NWS is the "official" source of forecasts and warnings.

2. "I struggle in accepting that you are using their basic spotter guide as an official source of meteorological definitions."
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It's an official training guide for Skywarn Spotters and is part of the official NWS training course. Therefore that's what I use. Feel free to disagree if you will, but I'll stand by it.

3. "We weren't talking about warnings, we're talking about the above picture. And for that, the AMS definition matters. There's no question it is a tornado "
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As I stated, it may technically be a tornado by the GOM, but that doesn't mean the NWS necessarily considers it one. They are the ones who have to verify it and they have the final say as far as storm classifications go.
I say again, if there's a discrepency with the GOM, take it up with the NWS and see if they'll change the Skywarn course. This is my entire point.

4. "I posted the official NWS definition, from the official NWS glossary. It makes no mention of REQUIRING a thunderstorm. Note the word "usually." That means there are times that the violently rotating column of air is NOT pendant to a cumulonimbus (thunderstorm) but is still classified as a tornado. If the NWS definition required a thunderstorm, they would have taken the word "usually" out."
======================================================
Given, we're in agreement on this one. Your post said the NWS definition makes no mention of cumulonimbus (thunderstorm), that was what I was referring to. Most people use the terms thunderstorm and cumulonimbus interchangeably, thus the informal definition most definitely mentions a thunderstorm.

 

[rdale]

Originally Posted by rdale
As I stated, it may technically be a tornado by the GOM, but that doesn't mean the NWS necessarily considers it one. They are the ones who have to verify it and they have the final say as far as storm classifications go.
I say again, if there's a discrepency with the GOM, take it up with the NWS and see if they'll change the Skywarn course. This is my entire point.

I think there are some wires crossed in our conversation

This is the official NWS definition. The verbage that they use to define a tornado, regardless of what is produced in slimmed-down pamplets for the public.

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

They define a tornado WITHOUT the need for a thunderstorm. "Usually" - but not "required." Using the NWS definition of a tornado, the above picture is a tornado.

 

[Damon Poole]

Yes, we agree on that point, and the definition. Cold air funnels are technically non-mesocyclonic tornadoes, (aka, a landspout, when they rarely do touch down), as in this case. Thus, they do not require a thunderstorm. I never said that wasn't true. I simply stated the definition in the spotter's guide, which focuses on the mesocyclonic type. In this particular case, I agree that this is a landspout.
Because landspouts are usually weak, they do not generally cause much damage (except in rare cases like this one), and usually dissipate as quickly as they form. As a result, and, as I, and others have stated before, the NWS may or may not consider these basis enough to issue a Tornado Warning, especially if there is no doppler indication at the time a spotter report is recieved. Hopefully this will finally untangle the wires and end any confusion or disagreement.

I think there are some wires crossed in our conversation

This is the official NWS definition. The verbage that they use to define a tornado, regardless of what is produced in slimmed-down pamplets for the public.

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

They define a tornado WITHOUT the need for a thunderstorm. "Usually" - but not "required." Using the NWS definition of a tornado, the above picture is a tornado.

 

[scott r currens]

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

Translation: We aren't able to forecast and warn for them so it isn't a tornado.

That is not good enough! Just because it is very difficult to forecast doesn't change what it was. It was a tornado plain and simple. The tornado was a non-mesocyclone tornado but is doesn't change the fact that it was a tornado.

Dust Devils and true gustnadoes are not connected to deep moist convection and have absolutely nothing to do this tornado.

The argument that non-mesocyclone tornadoes are weak and rarely do damage doesn't hold water. The vast majority of mesocyclone tornadoes are weak and don't do damage. We still call them tornadoes. The only real difference is that non-mesocyclone tornadoes do not produce EF-4 or EF-5 damage.

Call me crazy, but a vortex type (non-mesocyclone tornado) that meets the definition of a tornado and is capable of producing EF-0 to EF-3 damage should always be called a tornado, even when it is not convenient. Remember, EF-1 tornadoes can and on occasion do kill people. It is not uncommon for non-mesocyclone tornadoes (landspouts) to produce EF-1 or EF-2 damage. Wind is wind and it doesn't matter what type of tornado hits you. Mesocyclone or not, this is what your residence can look like if a 5-minute weak (EF-1) tornado gives you a visit.