gustanado and landspout predictions?

[Jason Harris]

Was just reading "NON-SUPERCELL TORNADOES: A REVIEW FOR FORECASTERS
http://www.srh.noaa.gov/topics/attach/html/ssd96-8.htm
and struck by how some gustanadoes can do F1 damage and this statement "Studies have revealed that while most gustnadoes are undetectable, in a few cases they have been identified using radar"--and wondered if anyone here has actually looked on radar and thought something along the lines of Hmm, could be some gustanadoes or landspouts, let's go see.

Also, noticing in FL right now the warning of 60+ mph winds but what looks not too impressive except for a couple meso markers, and what I would think would be a gust front with some shear. Is this the sort of setup where you would expect a gustanado if anything? (would you just try to pick through the pixels of opposing winds--seems like it could be a needle-in-a-haystack. . . .)

"Studies have revealed that while most gustnadoes are undetectable, in a few cases they have been identified using radar. Such occurrences are limited to gustnadoes within about 25 mn of the radar, and the majority of radar-detectable gustnado circulations have been confined to the lowest 1 to 2 km above the ground (Brandes 1993, Vasiloff 1993, and Stumpf and Burgess 1993)."
Perhaps that's the same Stumpf who posts here? Further updates on this?

Any radar captures of gustanadoes and landspouts?

 

[Dann Cianca]

Can't say anything about gustnadoes, but the Denver-area landspouts are often well represented on RADAR. I have a nice velocity image on my blog from this summer where you can see the couplet of the landspout. KFTG is right in the landspout/(DenverConvergenceVorticityZone)alley.

http://blog.bigskyconvection.com/2008/08/denver-landspout.html

 

[Keith Mullen]

Gustnado v Landspout

Sorry for interjecting, but I assumed that gustnadoes and landspouts were two different creatures altogether.

Perhaps someone could also help clarify this to move the thread forward a bit, but I was under the impression that gustnadoes were typically formed by the interaction between outflow (typically ffd) winds forcing against inflow or stationary forcing, causing a temporary vortex at (typically) surface levels that gives the appearance of a weak tornado, and

landspouts are "tornadic events" that occur from severe storms that don't have the characteristics of a mesocyclone/rotating supercell, the tornado itself being formed from: strong lower level shear and strong updrafts above, cold pool aloft, and other mechanisms of forcing & rotation OTHER than a strong, persistent, rotating, updraft throughout the storm column.

...not to mention some weak tornadoes that happen to form in conditions where visible funnel condensation and relative storm speed are on the low side... that travel through a dusty field & become visible, are just going to be labeled as a landspout anyway upon sight.

Clarification anyone? Thanks...

 

[Jason Harris]

No one suggested that gustanadoes and landspouts were the same--check out the article NON-SUPERCELL TORNADOES: A REVIEW FOR FORECASTERS with the link above; it's got a good chart with some basic comparisons, and makes distinctions like this:

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Landspouts form when pre-existing horizontal circulations are stretched and tilted upward by a developing thunderstorm updraft (Figs. 2 and 3). As with gustnadoes, landspouts do not usually form from mesocyclones or supercells. In fact, a large number of landspouts are observed in association with lines of cumulus congestus or towering cumulus clouds, often before precipitation is visible on radar. However, storm interceptors have noted the presence of landspouts in conjunction with supercell thunderstorms, sometimes at the same time as, but in a different part of the storm than a supercell tornado.

Landspouts are usually visible, unlike gustnadoes, and most have a narrow, rope-like condensation funnel extending from cloud base to the ground. Wall clouds are not usually observed with landspouts, and these tornadoes are typically short-lived and weak. Damage associated with landspouts can be significant, however, with damage in the F1 category not uncommon. Vasiloff (1993) noted a landspout which reached F2 intensity.

Although typically thought of as a High Plains phenomena, landspouts occur in other regions, including the Southern Plains and the Mississippi Valley. Rogash (1990) detailed the occurrence of a tornado in northeast Arkansas that, judging by its appearance and development, was most likely a landspout. The synoptic and mesoscale environments that favor the development of landspouts in the High Plains also exist in other regions; the higher number of landspouts in the Plains may be attributable to the fact that they occur in drier environments and therefore are easier to see.

--- not sure what the limit is on how much I can quote from an article, but here's some more on gustanadoes from the link:

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Gustnadoes typically appear as a swirl of dust or debris along the leading edge of the thunderstorm outflow. There is usually no condensation funnel or other visible connection to the cloud base above. Since they develop along the leading edge of a storm, gustnadoes are not usually associated with a wall cloud or rain-free cloud base, therefore, these tornadoes are typically extremely difficult to identify visually. Some ground-based circulations associated with thunderstorm outflow can become more intense and more closely resemble a "traditional" tornado (that is, they fit the Glossary definition).

The gustnado is typically associated with bow echoes or squall lines, and should not be confused with tornadoes that may develop in the rotating portion of the bow echo which Fujita refers to as the comma head (Fig. 1). The latter tornadoes, as noted by Pryzbylinski (1995) and others, are often associated with a mesocyclone circulation that develops as the bow echo evolves into a comma echo

And thanks for the radar capture Dann!

 

[Keith Mullen]

Thanks

Much more eloquently and accurately put than my quick jotting down. Thank you very much.

Now you have me curious as to whether there are any indicators of gustnadic (sp?) conditions that would really mean anything or have some weight behind it?

Great, one more thing for me to ponder. lol