Landspouts and Tornadoes

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

Neither landspouts nor tornadoes show up on radar...

- Rob
 
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.
 
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
 
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...
 
"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.
 
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.
 
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?
 
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.
 
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.
 
"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.
 
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


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.
 
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 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
 
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).
 
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.
 
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
 
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.
 
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
 
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.
 
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. :)
 
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.
 
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..
 
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