Landspouts and Tornadoes

[Andrew Khan]

I am striving to figure out if there is a way to differ a landspout and a tornado, visually. I am also wanting to know, does the NWS put out LSR's for landspouts. I see the NWS doesn't have warnings for landspouts as well...landspouts however, can be damaging, and deadly. There is a conspiracy about how they're different, some people think they're the same, but I'm trying to be able to figure out how they differ based on visual evidence. Another thing, do Landspouts have a specific Reflectivity on Radar, that is unique?

Thanks

[Marko Korosec]

Andrew,
if this helps; taken from NWS tornado FAQ (http://www.spc.noaa.gov/faq/tornado/):

[i][list]
Marko

[Andrew Khan]

Oh, okay. That definition helps me a lot. Thanks!

[rdale]

"Another thing, do Landspouts have a specific Reflectivity on Radar, that is unique?"

Neither landspouts nor tornadoes show up on radar...

- Rob

[Andrew Khan]

I really was not insinuating a tornado did. But, there are some specific reflectivity signs, that show tornado initiation, not whether or not is in contact with the ground or not. For a tornado the signature would be a Hook Echo, and the tornadogenesis Couplet, and I am trying to figure out if the landspout has a specific radar unique to itself.

[rdale]

Again a slight correction... A hook echo has nothing to do with tornado initiation, it's just a sign of rotation in the storm. You'd want to look at velocity imagery for a better view, but still no matter how impressive the rotation looks in either image you still cannot conclude that a tornado is forming.

Landspouts do not have the associated storm-scale rotation that a tornado has...

- Rob

[Andrew Khan]

Right, a hook echo deals with extremely tight strong rotation, that could in fact produce a tornado, nothing is for sure though, I know this. But it is a trademark of a lot of tornadoes, whether it be an indicator or not, it does in many cases, mark tornadogenesis. I realize a good way is to look for a couplet in a velocity scan...

[Andrew Khan]

"A "landspout" is storm observer slang for a non-supercell tornado, most often seen in relatively dry enviromnents with weak wind shear and high-based thunderstorms. On this day, vertical shear favored supercells (and one did develop farther south); however, the process behind this tornado was not that of a mesocyclone. Such tornadoes typically take shape as a translucent dust column, like this, sometimes beneath funnel clouds, unlike this."

Looks like a lot of landspouts do not have full condensation funnels reaching to the ground.

[Andy Wehrle]

To clarify what Rob is saying, landspouts do not have the radar signatures normally associated with tornado production. The storms often have weak reflectivity values and no hook echo, and if a velocity couplet shows up it will be very small and only show up right at or after the time of landspout formation.

[Andrew Khan]

So, do people report landspouts to the NWS office at ALL, and if they do, do they say 'tornado' or 'landspout'? Why are these so common in Colorado?

[Andy Wehrle]

Yes, landspouts are (and should be) reported to NWS offices, as "tornado" reports. Landspouts are tornadoes even though they do not originate from storm-scale rotation and tend to be weaker than those that do.

A landspout is not to be confused with a gustnado which rotates only at ground level, not at cloud level as well. Therefore, a gustnado is not a true tornado.

I don't know exactly why landspouts are common in Colorado. Someone who chases there can answer that question.

[Mikey Gribble]

A landspout is not associated with a mesocyclone and it is not going to show a velocity couplet like a supercell tornado. The way I understand it, landspouts usually form because of small circulations(often times terrain induced) along a boundary. When these small circulations are under a convective updraft landspouts can form throgh vortex stretching. The landspout would visually look different for a couple reasons. With tornadoes, there is usually a broad area of rotation in the updraft base before and during the tornado. With a landspout there would not be much if any rotation in the updraft base above the landspout. There is no mesocyclone. Also, a landspout is typically weak when compared to a tornado.

[Mikey Gribble]

"I don't know exactly why landspouts are common in Colorado."

They are common because of the terrain. The Palmer Divide causes a convergence zone and these small circulations along the boundary(that I mentioned in my previous post) lead to landspouts when they get pulled into a convective updraft.

[Jeff Snyder]

Michael covered it pretty well. Landspouts derive their rotation from strong pre-existing horizontal shear along a boundary. Oftentimes, there are relatively small-scale circulation centers (misocyclones, with an "i" instead of an "e") that develop... If a convective updraft moves or develops over such an area, the updraft can stretch the existing shear and produce a landspout. Unlike a supercell tornado, a landspout can develop from showers or even towering cumulus (cumulus congestus).

Bruce D, and Robert B. Wilhelmson, 1996:The Numerical Simulation of Non-Supercell Tornadogenesis. Part I: Initiation and Evolution of Pretornadic Misocyclone Circulations along a Dry Outflow Boundary
(http://ams.allenpress.com/amsonline/?request=get-abstract&doi=10.1175%2F1520-0469(1997)054%3C0032:TNSONS%3E2.0.CO%3B2)

A Google search for "non-supercell tornado" and "misocyclone" turns up quite a few hits, though mainly AMS publications, which require a username/password to view anything other than the absract.

[Marko Korosec]

Michael, Jeff,
so if I understood you right...landspouts can also develop from showers with a usual front pass. I posted this topic: http://www.stormtrack.org/forum/viewtopic....ighlight=#90548 (http://www.stormtrack.org/forum/viewtopic.php?p=90548&highlight=#90548) few weeks ago with some pics of rotating wall cloud, we came to conclusion that it was a tornado, probably a multi-vortex tornado.

But later I realised that there were no supercells (or a mesocyclone) that day, only a normal cold front pass. But I've noticed a few condensation funnels that reached the ground, there were heavy showers the whole day too.

So now I am a bit confused, seems those were landspouts...the thing that confuses me is that there were few of them, so can they occur as multi-vortex (landspouts) even there is no supercell storms?

Thanks,
Marko

[Greg Stumpf]

Originally posted by Andrew Khan
Looks like a lot of landspouts do not have full condensation funnels reaching to the ground.
Not necessarily. Perhaps the majority of non-supercell tornadoes on the High Plains lack condensation funnel, but that's only a result of the lower RH values around these storms. Non-supercell tornadoes are probably the more common mode of tornado in the sea-breeze regimes of the southern U.S. Gulf and Atlantic Coasts (e.g., Florida), and most of those non-supercell tornadoes have full condensation funnels (higher RH).

[Jeff Snyder]

Your pictures certainly don't look like the "average" landspout. In addition, I've never heard of a multivortex landspout, and I'd think that, given the processes that form landspouts, it certainly isn't very likely. I'd think that you would need three very concentrated areas of horizontal shear in very close proximity to develop something like that (but taht would be more like three distinct landspouts in close proximity, not really "multivortex" as we think of it today). Perhaps the storm that spawned that tornado wasn't a supercell, but it may have been able to develop strong low-level rotation (if it did have rotation) by the tilting and stretching of vorticity to develop a low-level mesocyclone. If the storm wasn't a supercell, it may have been some other type of nonsupercell tornado. I'm not sure anyone has really developed a distinct classification for nontornadic tornadoes, though I would consider landspouts and gustnadoes certainly to be two "types". In the end, the stretching of vertical vorticity (regardless of whether or not that resulted from the tilting of horizontal vorticity) by some sort of updraft concentrates the rotation, which can lead to a tornado.

I'm very far from an expert in this, so I hope someone who knows this process better than chime in.

EDIT: When I say a tornado associated with a supercell, I am implying that the tornado is a associated with the mesocyclone. As Amos notes below, it is important to remember that not all tornadoes produced by supercells are necessarily associated with the mesocyclones. Indeed, supercells can produce non-mesocyclone tornadoes.

[Glen Romine]

There is nothing related to the parent storm that dictates whether a tornado will have a single core or multiple vortices. For the dynamically inclined, recall that even dust devils have been observed to have multiple vortices, and it is the ratio of radial to tangential winds within the tornado vortex itself that determines its structure, not whether the larger environment is characterized by a vortex sheet (~landspout) or a swirling flow (~mesocyclone). I'd also caution that just because a tornado is observed with a supercell doesn't mean the tornado wouldn't have formed the same way had the convection been ordinary. Supercells can generate tornadoes outside of the mesocyclone region. A fairly famous example of an intense 'landspout' tornado is the Jarrell Texas case - which was a hybrid supercell/multicell storm, but the updraft was simply stretching merged vortex sheets associated with several intersecting boundaries. I'd also add that you can ocasionally see shear signatures on radar from non-supercell tornadoes - though it seems the signatures are rarely detected prior to the tornado developing. There are papers out there on all this stuff if anyone is interested in formal references.

Glen

[Andrew Khan]

So if there was a landspout right now, would I be able to look at it and visually infer whether or not it was in fact a tornado or a landspout? I understand now why they are so common in CO, but I am wondering why I don't see many 'Tornado' reports in CO, for landspouts. I wonder if people just don't call them in.

[nickgrillo]

Originally posted by Andrew Khan
So if there was a landspout right now, would I be able to look at it and visually infer whether or not it was in fact a tornado or a landspout? I understand now why they are so common in CO, but I am wondering why I don't see many 'Tornado' reports in CO, for landspouts. I wonder if people just don't call them in.

On many cases, you can tell visually if it's a landspout or a tornado.

Landspout (see how hollow-looking it is? Almost like a waterspout):
http://www.chaseone.com/060103vid07.jpg

Mesocyclone "real" tornado:
http://midwestchase.com/9-June-2005/tn_692...05628PM0003.jpg (http://midwestchase.com/9-June-2005/tn_692005628PM0003.jpg)

[Andrew Khan]

Thanks Nick, pretty clear now. It looks transparent like a waterspout as you said. Thanks.

[Jeff Snyder]

I'd be VERY cautious about using the "if it appears transparent then it's a landspout" idea! Some of the "transparency" is more of a function of moisture availability, and I'd think some of it would be tied to the pressure pertubation of the vortex. I've seen numerous supercell/mesocyclone tornadoes that have lacked full condensation to the ground or have appear semi-transparent (translucent). I believe the Sharon, KS, tornado on 5-12-04 looked much this way. More often than not, landspout tornadoes will look like a slender tube with little taper to the funnel (like a Pringles can) as compared to many mesocyclone-induced tornadoes, which can looked more taper (classic funnel shape). The shape of the tornado seems to be related to the height of the LCL/LFC in my experience, with more slender tornadoes associated with relatively high LCLs/LFCs, and larger, more robust-looking tornadoes associated with lower LCLs/LFCs. Just in my experience. As Glen noted, moisture is usually more limited in eastern Colorado, where many landspout tornadoes occur, which may be why these landspouts often look translucent and have the slender, cyclinder shape.

[Mark Farnik]

Hey Andrew,
I live in the heart of "Landspout Alley" about 80 miles northeast of Denver. What I can tell you as far as landspout reporting goes is that there are not very many people out here. Once you get northeast of Hudson( small town about 20 miles northeast of Denver that is fast becoming a suburb) there are only three towns of 5,000 or more people along I-76 all the way to Nebraska. There is a lot of open space (especially in northeastern Weld County, where there is more than 12,000 square miles of land with less than 600 people living on it) People out here tend to ignore landspouts, as they are so common that everyone is used to them and knows that as a whole, they generally don't do much damage. Also, there are very few storm spotters out here, and the general public rarely bothers to report them.
As far as formation, there are several factors which come into play. First, we have a semi-arid climate and rarely have dewpoints above 60 degrees except for near the Kansas border, and then once you cross into Kansas you'll immediately run into much deeper moisture. It seems that the 60 + dewpoints just cannot hurdle the state line. Therefore, without the deep moisture, it is difficult to get the extreme instability required for a typical tornado outbreak you might see even in far western Kansas. CAPE's of 3000 or more are rare anomalies around here. Also, around here we get what we call the "Denver Cyclone." It forms over or just east of the Denver metro area when the eastern plains come under southerly or, more typically, southeasterly flow. It is an orographically induced vortex and can last a good period of time. It often spins off what is called the DCVZ, or Denver Convergence Zone, along which supercells can rapidly erupt under favorable spring or summertime conditions. The storms that form along this convergence zone come under the influence of the converging winds at various heights along the zone, and as they grow and develop landspouts can and often do form. Storms that produce mesocyclonic tornadoes can also form along this boundary, though they are far less common :( and the tornadoes are usually much weaker than tornadoes forming from a similar storm under similar conditions 150 miles further east in the Great Plains.
The storms here have a tendency to be high based, most likely because of the lower dewpoints and higher elevation, with the LCL's usually quite high out here, (hmm, wonder if that's why they call it the "High Plains" :lol:) which for the most part precludes the formation of any significant tornadoes in eastern CO; that isn't to say we never have significant tornadoes around here, but they are much less frequent here than in western Kansas or Nebraska. Violent tornadoes are almost unheard of. The only one in recent memory was the F4 that plowed through Limon, a small town of about 3,500 souls 100 miles southeast of Denver, 15 years ago on June 6, 1990. I guess it's a blessing and a curse. I can't wait until I get my driver's license January, because that means next spring I can head for the Heartland and catch some real tornadoes (barring another seemingly tornado-less spring and summer like this one was :evil: ) instead of chasing Colorado's weak, oversized, connected-to-the-cloud-base vorticies with an identity crisis(Am I tornado or am I a dust devil?) Oh, I mean "landspouts"; sorry if that wasn't politically correct :roll:
This is what I have learned over the past 15 years growing up in "Landspout Alley."
I hope this explanation was helpful to you. :)

[Andrew Khan]

So, I guess this is why I fail to see any 'tornado' reports in the CO area. I understand they are induced by orography, and it gets very interesting, and mysterious to me, almost thrilling. I always love weather rendered by orography. But I guess Landspouts 'could' potentially be strong. I mean if the CO residents take it lightly, and then there is a tornado, then they'll be regretting there decision. So the Denver Cyclone is just an annual occurance of an orographically induced tornado/vortex? I guess chasing landspouts would be tough since I assume they are short-lived. Do you guys see many Orographic Clouds out in that area? I think it's really neat how CO is so vulnerable to landspouts, it's just amazing how orography can do all this.

[Kurt Hulst]

There are tornadoes that can be transparent but youll notice a definete funnel above. The Medicine Lodge May 12, 2004 and Medalia MN 2005 were both very transparent but definetly a tornado. Just thought i would point that out that not all transparent tornadoes are landpouts in a previous post above it sounded misleading that all translucent/transparent circulations were landspouts..

[Andrew Khan]

Yeah, I had a video of the Medicine Lodge Tornado, and that was one of the things I noticed...that was a cool tornado. So it sounds like an 'iffy-buisness' to start differentiating them..

[Greg Stumpf]

Differentiating non-meso tornadoes with meso tornadoes has to do more with visual storm structure than the tornado structure. As I and others have tried to point out, the degree to which a condesnation funnel forms is more a function of relative humidity and the pressure drop in the vortex core rather than a function of tornado type.

Many non-meso tornadoes that I have witnessed appear to eminate from the a portion of a newly developing updraft rain-free base (RFB), sometimes as pointed funnels in the middle of an RFB with the dust sheath connecting. Sometimes they eminate along the flanking line RFB of a supercell, but not directly with the low-level mesocyclone.

Mesocyclone tornadoes are characteristically associated with the classic low-level mesocyclone features of a supercell, including (but not always) the wrapping rear-flank or occlusion downdraft clear slot, occluded low-level mesocyclone, and wall cloud.

And then there are what I call hybrid tornadoes, that occur somewhere on a continuous spectrum of mesocyclone and non-mesocyclone tornadoes. The tornado that hit near the old Denver Stapleton airport on 15 June 1988 (http://ccc.atmos.colostate.edu/~hail/cool/tornados/images/ad42_denver_tornado.jpg) appeared to develop like a classic non-meso tornado, but then slowly morphed into something more akin to a mesocyclone tornado, with a wrapping clear slot around the west and south side (although I admit that this was closer to the non-meso tornado side of the spectrum for the most part).


greg

[Andrew Khan]

But then you have to consider, thae perhaps the storm structure might not be visible, due to precipitation, or haze at the time. Which, could make for guessing or death.

[Greg Stumpf]

Originally posted by Andrew Khan
Which, could make for guessing or death.
Any tornado can kill, so what difference does it make if it is non-meso or meso induced in terms of protecting life?


g

[Andrew Khan]

Yes, I'm sure any tornado could kill someone.....What I was really saying it would help for reporting, and also for protecting life, because of it was a non-meso tornado, chances of survival might be increased, not that they are not diminished.

[Mark Farnik]

Andrew
People around here are absolute fools when it comes to tornadoes. Since we so rarely have damaging tornadoes, people blow off the warnings 90% of the time. Take for example my hometown, Fort Morgan. Established in 1884, the city has never been hit by a tornado or otherwise damaged by a natural cataclysm. There was one that came close on May 30, 1996, a high end F2 that could have caused considerable damage had it moved into the city but it hit some farms about three miles south/southwest of town. Other than that nothing. The 12,000 residents have been lulled into a false sense of complacency, and my worst fear is that someday a strong tornado will hit the city and people will die because they didn't heed the warnings. The worst thing is we have a grand total of 6 mobile home parks across the city; three on the south side of town, one on the southwest and two on the north. One of the parks on the south side of town has over 300 units, it is sprawled over six square blocks and is just a tragedy waiting to happen. And they aren't exactly weatherwise, either.
I have a bad feeling that eventually there will be a strong tornado, whether it be mesocylconic or non-mesocylonic, somewhere along the Front Range, as the subdivisions relentlessly march eastward into the plains, especially along the I-70 corridor, and that there is the potential for a real tragedy to occur in a town like Bennett, Strasburg or Deer Trail.
As far as the Denver Cyclone frequency, it occurs about 5-15 times during the spring and summer months.
In regards to orographic clouds, yes, we do have them frequently, especially in the wintertime, when you get westerly flow blasting over the mountains, sculpting the clouds into exquisite curves and shapes. They are truly awesome to observe and are especially stunning when backlit by the setting sun. The orography of the eastern plains of Colorado is unlike any other place in the world, and I feel truly blessed to dwell here and observe the unique phenomena spawned by the unique geography we have here(well, most of the time anyway) :)

[Andrew Khan]

I absolutely love orography, it is interesting to here that so many people are unaware about tornadoes, it makes me feel like where I live. How big is your town (population)? I guess it's a small town. CO's geography is amazing, and they get some cool stuff there. But you guys in your town 'have' landspouts right, or just 'around' you? I am trying to find some orographic clouds around my area that I am 99.9% sure we get. Since I live RIGHT beside the Appalachian Mountain Range, and then the Cumberland Plateau. Any advice?

[Mark Farnik]

Andrew
Quoting myself:
The 12,000 residents have been lulled into a false sense of complacency
That's OK. You probably just missed it by mistake. :)
As far as looking for orographic clouds, look for them in late fall and winter, on mostly clear days when the jetstream is directly or nearly directly overhead.
This is a helpful link you might want to check out:
http://atschool.eduweb.co.uk/kingworc/depa...orographic.html (http://atschool.eduweb.co.uk/kingworc/departments/geography/nottingham/atmosphere/pages/orographic.html)
From the info on that site, I'm guessing that if you are on the lee side of the Appalachians/Cumberland Plateau, you should get some pretty awesome clouds under the right conditions. Not quite as dramatic as the lenticulars we get out here, but still nice spectacles.

[Andrew Khan]

Thanks man. I think I will likely go out there over this fall/winter. But, I'm not sure how to track down the Jetstream, to make sure it's over the mountains when I go. How do I go about doing that? I guess, it's just luck then right? You either go, and get awsome clouds, or go and get nothing.

[Mark Farnik]

You've got the jist of it. Excellent!
To everyone else, Andrew and I apologize for deviating from the main topic significantly. We young weather nerds tend to do that on occasion. :D

[Andrew Khan]

LOL, thanks for the help Mark, and everyone else!