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Dann Cianca
04-11-2008, 10:01 AM
Hi,
I just wanted everyone's opinion on this. On April 9th, a "cold air funnel" was reported near Kalispell, Montana in the vicinity of a field of showers (Radar: http://www.rap.ucar.edu/weather/radar/displayRad.php?icao=KMSX&prod=bref1&bkgr=black&endDate=20080410&endTime=1&duration=2). I'm not disputing the fact that it may be a "cold air funnel", though I wouldn't rule out a landspout. But from the image, it is obviously touching the ground. Would that not make it a tornado, even if it is a NST/landspout?

News Story Here: (with image)
http://www.dailyinterlake.com/articles/2008/04/11/news/news03.txt


Missoula, MT NWS LSR:

NWUS55 KMSO 101933
LSRMSO

PRELIMINARY LOCAL STORM REPORT
NATIONAL WEATHER SERVICE MISSOULA MT
133 PM MDT THU APR 10 2008

..TIME... ...EVENT... ...CITY LOCATION... ...LAT.LON...
..DATE... ....MAG.... ..COUNTY LOCATION..ST.. ...SOURCE....
..REMARKS..

0630 PM FUNNEL CLOUD 4 NW KALISPELL 48.24N 114.37W
04/09/2008 FLATHEAD MT PUBLIC

PUBLIC TOOK PICTURES FROM COSTCO PARKING LOT OF COLD AIR
FUNNEL OR LAND SPOUT THAT TOUCHED THE GROUND IN AN OPEN
LAND AREA NEAR KALISPELL. NO DAMAGE WAS REPORTED.





Correct me if I'm wrong ...

Thanks,
Dann.

rdale
04-11-2008, 10:17 AM
No doubt that should be logged as a tornado...

Billy Griffin
04-11-2008, 10:36 AM
I've seen a few of those in Washington, near the PSCZ and out east of the Cascades. Yet the local NWS offices still consider them NOT to be tornadoes.
I've kind of given up on calling them in for this reason, but still enjoy the catch in a "not so typical" geographic location in the US.

I'd call it a tornado.

Dann Cianca
04-11-2008, 12:28 PM
This reminds me of a time in my youth. It had to be in the mid to early 90's while growing up in Butte, Montana. It was a similar day ... showery weather, grauple if I remember right. I ran outside due to a call from my father saying there was a funnel cloud. Sure enough, there it was to the south of town. There was a ton of congestus with snow showers. It was documented in local media and many people witnessed it (though to this day, there seems to be no record available on the internet: I've searched high and low)

A few witness reports said that it touched down, but there was never an official tornado report from it. I wonder if it was a similar situation and the weather service (missoula) had a specific protocol regarding "cold air funnels".

I'd love to find more info on that old case.

Tim Shriver
04-11-2008, 02:02 PM
I agree with RDale. It extends from the base of a cloud, it is a violently rotating
column of air in contact with the ground. No longer a funnel at all.

We had a number of them toss cars around at a dealership some years back. They
can do some damage, though rare.

Tim

Shane Adams
04-11-2008, 04:32 PM
If it's on the ground it's not a funnel.

If it's connected to a cloud base (regardless of any other 'severe weather' ongoing from the same area) it's a tornado. I know the scientific reasons are different, but the result of this "cold air funnel" is no different than a landspout.

I'm tiring of these cases....I think it should just be a "tornado" and call it a day. Those who lose sleep over full condensation and f-strength can do the extra leg work to sift out the "fake" tornadoes from the data.

Dann Cianca
04-11-2008, 05:06 PM
We could make up all sorts of new classifications ... cold air tornadoes ... medium air tornadoes ... luke warm air ... etc. I e-mailed the local NWS for clarification (as it seemed like the newspaper had talked to them for the article). If they're not busy, maybe I'll see a response.

Kenny Drake
04-11-2008, 05:21 PM
The problem is when the public see's "tornado reported" they think of a tornado that is going to destroy stuff. I'll drive through such a landspout/tornado/vortex anyday.

Shane Adams
04-11-2008, 06:01 PM
You're a braver man than I. Landspouts seem so harmless but man they can get going as well some strong tornadoes. Maybe I'm just a wimp.

Dann Cianca
04-11-2008, 06:22 PM
The problem is when the public see's "tornado reported" they think of a tornado that is going to destroy stuff. I'll drive through such a landspout/tornado/vortex anyday.

I've heard a lot of retarded things in my day ... *ahem*

... most if not all the tornadoes that the Denver metro-area see are landspout (non-supercell tornadoes) One such event in 1988 produced 4 nst's, two rated at F2 and one F3. (Szoke 2006*) A furniture store was heavily damaged as well as many homes near Broadway/Evans.

So, tough guy, before you drive through any such landspout/tornado/vortex please consider the taxpayers who will foot the bill of the emergency crews called to cut you out of your destroyed chase vehicle.

Thanks in advance.


*THE DENVER CYCLONE AND TORNADOES 25 YEARS LATER: THE CONTINUED CHALLENGE OF PREDICTING NONSUPERCELL TORNADOES
Edward J. Szoke 2006

Nigel Bolton
04-11-2008, 07:04 PM
These type of manifestations occasionally occur in the UK in the summer. They normally occur within a slack area of low pressure that is filling, but contains rPm air that is quite moist. The slack area of low pressure is nomally coincident with an upper cold pool, with light winds throughout the depth of the convective atmosphere. Convergence, such as sea breezes or decaying fronts assists the development of these phenomena, but as soon as precipitation forms within the cloud that they are pendant from, they readily collapse

Normally these appear as just funnel clouds, but occasionally they do touch down, but are generally very weak and cause little damage. However, one, whose damage I investigated back in 1991 almost destroyed a well built stable, seriously damaged trees, took out a wall, overturned a medium sized lorry, as well as other misdemenours. It attained a strength of T3, roughly the top end of an EF1. However these types of tornadoes, and that IS what they are, very rarely last for more than a few minutes on the ground as friction overcomes their weak circulation.

N.

Jim Saueressig
04-11-2008, 09:30 PM
I would certainly call it a tornado.

I came across one on the ground in a field South of Guymen Ok in 2005 while heading to CA. It was rolling through a field right on the ground near the power sub station you see next to the tree line. I called it in to the local sheriffs office and they sent a trooper out within 5 minutes who was a trained weather spotter for the county and could still see it in funnel form.

I let him know it had been on the ground and nearly dissipated and was again then re strengthening as he watched. He notified dispatch who was already on the phone with the weather service. Based on their radar they refused to issue a warning because it couldn't be there even though it was on the edge of town. Needless to say the trooper was very upset about the warning refusal. This never touched down again but did persist in funnel form another 5 plus minutes pulling up and dropping over houses before it finally died out.

http://www.troubledhorizons.com/funnels/landspout001.jpg

Personally I believe it should have been issued as well. It was strong enough on the ground to toss things around that would be big enough to possibly maim or kill someone especially in a populated area. Has it been out in the open country it would have been no problem.

Brian Stertz
04-11-2008, 09:53 PM
Yeah no doubt tornado Dann...in fact.....the caption under the photo is a really poor piece of journalism. Blatantly saying "no this is not a tornado" when clearly this tornado is on the ground raising a debris column. Then this odd factoid "Those that do reach the ground behave like weak tornadoes, with winds often 50 mph or slower." Not sure where this comes from. :confused:

Damon Scott Hynes
04-11-2008, 10:35 PM
The first time one of these cold-air funnels flips a school bus over is the last time they don't get warned for.

Dann Cianca
04-12-2008, 01:51 PM
Thanks for having a look, gentlemen. You'd think that they would be especially sensitive to tornadoes in the area after a supercell tornado did a lot of damage in the town of Polson (on the south end of Flathead Lake ... where Kalispell is on the north end) before heading out onto the lake as a "supercell tornado over water" and capsizing a boat. That was pretty big news in the area last year.

rdale
04-12-2008, 03:28 PM
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
04-12-2008, 05:34 PM
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
04-13-2008, 03:14 PM
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
04-13-2008, 03:53 PM
I've never heard that explanation... I wonder where that came from?

Dann Cianca
04-13-2008, 03:58 PM
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
04-15-2008, 06:06 PM
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
04-15-2008, 06:50 PM
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
04-15-2008, 08:03 PM
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
04-15-2008, 08:58 PM
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 (http://amsglossary.allenpress.com/glossary/search?id=cumuliform1) cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud (http://amsglossary.allenpress.com/glossary/search?id=funnel-cloud1)."

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
04-15-2008, 08:58 PM
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
04-15-2008, 11:12 PM
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
04-15-2008, 11:46 PM
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
04-16-2008, 07:13 AM
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
04-16-2008, 10:14 AM
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
04-16-2008, 10:38 AM
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.

Dann Cianca
04-16-2008, 11:21 AM
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
04-16-2008, 12:55 PM
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
04-16-2008, 03:38 PM
Have there been any confirmed injuries or deaths related to dust devils in the past?

Brent Gilles
04-16-2008, 09:13 PM
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
04-16-2008, 10:10 PM
---
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
04-17-2008, 11:07 AM
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 (http://amsglossary.allenpress.com/glossary/search?id=cumuliform1) cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud (http://amsglossary.allenpress.com/glossary/search?id=funnel-cloud1)." -

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
04-17-2008, 11:21 AM
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 :D


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
04-17-2008, 12:24 PM
Originally Posted by rdale http://www.stormtrack.org/forum/images/buttons/viewpost.gif (http://www.stormtrack.org/forum/showthread.php?p=174128#post174128)
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."
================================================== ====
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 :D"
================================================== ===
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
04-17-2008, 12:49 PM
Originally Posted by rdale http://www.stormtrack.org/forum/images/buttons/viewpost.gif (http://www.stormtrack.org/forum/showthread.php?p=174128#post174128)
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
04-19-2008, 12:07 AM
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
04-19-2008, 08:56 AM
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. (http://www.violentplains.com/Update2006/20060916_37.jpg)