Gustnadoes
Marc Foster
not seeing Greg Stumpf anywhere in sight, I thought I'd go ahead and offer
a definition/my best understanding of what a gustnado is...
Gustnadoes form on the leading edge of thunderstorms, where the outflow
boundary/gustfront is located. Now if you have a dust devil or some
similar broad low power circulation ahead of the gust front, the interaction
of the front with the circulation stretches the vortex and narrows the
diameter. Since energy must be conserved, the angular velocity is forced
to increase (spinning figure skater bringing her arms close to the body).
This is the basic form of the gustnado. They don't normally have winds
in excess of F0, and don't derive their energy in the same manner as a
tornado, and since the circulation is not pendant to the base of the storm,
it is not a tornado (by definition). The only way they are visible from
the dirt raised by the winds.
A good example of a gustnado that a lot of people have seen is from the old
Nova episode years ago, where Lou Wicker is screaming "That is the wierdest
thing I've ever seen!!!" in reference to what appeared to be a tornado
hanging down from the front end of a thunderstorm. If you listen to the
details he describes, it becomes obvious they are looking at a gustnado...
Yo, Greg! Bail me out here if any of this is wrong...
Marc
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Greg Stumpf
>
>Good description. Many argue that a gustnado *is* a tornado beacuse it
>is a violently rotating column of air on the ground, but seem to forget that
>the definition of a true tornado says that this column of air is *pendant
>from the cumulonimbus cloud*. This does not mean, however, that you can have
^^^
>very damaging gustnadoes if conditions are met. Also, some gustnadoes can
>be entrained into the thunderstorm updraft, becoming tornadoes (or hybrids).
This should read "can't".
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Greg Stumpf - KB5LMU \ / Internet: gr...@nsslsun.nssl.uoknor.edu
Forecast Applications Research || Phone: (405) 366-0477 FAX: 366-0472
Room 249, National Severe || Disclaimer: I chase to learn, but it's fun!
Storms Laboratory || "Be Landspouty!"
1313 Halley Circle || "Everyone get good pictures!"
Norman, OK 73069 / \ "NSSL wants your video!"
Greg Stumpf
>Several people have sent me mail asking just what exactly is a gustnado, so,
>not seeing Greg Stumpf anywhere in sight, I thought I'd go ahead and offer
I'm here....(up on North Campus)
>a definition/my best understanding of what a gustnado is...
>
>Gustnadoes form on the leading edge of thunderstorms, where the outflow
>boundary/gustfront is located. Now if you have a dust devil or some
>similar broad low power circulation ahead of the gust front, the interaction
>of the front with the circulation stretches the vortex and narrows the
>diameter. Since energy must be conserved, the angular velocity is forced
>to increase (spinning figure skater bringing her arms close to the body).
>This is the basic form of the gustnado. They don't normally have winds
>in excess of F0, and don't derive their energy in the same manner as a
>tornado, and since the circulation is not pendant to the base of the storm,
>it is not a tornado (by definition). The only way they are visible from
>the dirt raised by the winds.
Good description. Many argue that a gustnado *is* a tornado beacuse it
is a violently rotating column of air on the ground, but seem to forget that
the definition of a true tornado says that this column of air is *pendant
from the cumulonimbus cloud*. This does not mean, however, that you can have
very damaging gustnadoes if conditions are met. Also, some gustnadoes can
be entrained into the thunderstorm updraft, becoming tornadoes (or hybrids).
>A good example of a gustnado that a lot of people have seen is from the old
>Nova episode years ago, where Lou Wicker is screaming "That is the wierdest
>thing I've ever seen!!!" in reference to what appeared to be a tornado
>hanging down from the front end of a thunderstorm. If you listen to the
>details he describes, it becomes obvious they are looking at a gustnado...
Is this the infamous "Wicker Vortex"? I had heard that it was really smoke
from a fire being stretched into the thunderstorm updraft, and not a true
vortex.
John R. Moore
In article <1992Jul23.1...@nsslsun.nssl.uoknor.edu> stu...@nsslsun.nssl.uoknor.edu (Greg Stumpf) writes:
]Is this the infamous "Wicker Vortex"? I had heard that it was really smoke
]from a fire being stretched into the thunderstorm updraft, and not a true
]vortex.
We had one here 2 years ago (during the SWAMP project) that looked so much
like smoke that the Guadalupe fire department sent out the fire trucks
to what they thought was a plane crash. It was actually a gustnado, and
was observed by the Arizona Thunderstorm Chasers. I was not with the chase
team but saw it anyway. It was quite wierd... it looked like a dark cloud
on the ground, with funnels extending upwards from it and ending in clear air.
It occurred where a strong gust front hit a mountain, and probably also
another gust front, at the same time. Pretty nifty... it was the wierdest
thing I've ever seen also.