Definition of tornado in question here.

[Greg Stumpf]

LOL, that is pretty funny. Word has it Greg has see a waterspout or two. But most of them were on Lake Ontario so I am sure they were nothing like the ones you see. I think he even has a picture of one during a LES event.

Yep - 4 years at SUNY Oswego will do that to you. Now that I finally have a photo scanner at home, I should post that winter-time spout pic.

I've also seen Florida Keys spouts. BTW - be aware that photogrammetry studies of H20spouts have founds winds of up to 140 mph! I wouldn't call that "fair weather".

 

[Robert Dewey]

Based on which part, deep moist convection or strong enough to do damage?

Both, but primarily deep moist convection.

As for the 140 MPH claim, that's pretty interesting. Was this in fact a "fair weather waterspout" or was it associated with a thunderstorm and/or mesocyclone? I guess I can imaging a fair weather waterspout getting that strong, just as I've seen some pretty "violent" dust devils that are also "fair weather" occurences.

 

[Greg Stumpf]

By the definition on Chuck's essay (not Chuck's definition, though), a gustnado is actually a tornado... It's violently rotating, and it's under a cumuliform cloud. I guess a dust devil that also occurs with a puffy cloud over head is a tornado as well.

By CADIII's definition, the vortex has to be embedded into and driven by the deep moist convection's bouyant processes.

A pure gustnado is not embedded in the convection, and is caused by mechanical forces along the shear zone at the leading edge of a gust front. These gust fronts can move very far away from the parent convection, but still cause gustnadoes.

A dust devil is driven primarily by dry convective processes.

But, there are hybrids. A gustnado could become stretched and ingested into an updraft. Even a dust devil, under unusual circumstances, could find itself under a developing updraft.

 

[Greg Stumpf]

Both, but primarily deep moist convection.

As for the 140 MPH claim, that's pretty interesting. Was this in fact a "fair weather waterspout" or was it associated with a thunderstorm and/or mesocyclone? I guess I can imaging a fair weather waterspout getting that strong, just as I've seen some pretty "violent" dust devils that are also "fair weather" occurences.

Can you locate for us a definition of a "fair weather waterspout"?

Every waterspout that I've observed has been connected to deep moist convection.

 

[Robert Dewey]

Can you locate for us a definition of a "fair weather waterspout"?

Every waterspout that I've observed has been connected to deep moist convection.

NWS: http://www.srh.noaa.gov/mfl/hazards/info/waterspouts.php

Fair weather waterspouts usually form along dark flat bases of a line of developing cumulus clouds. This type of waterspout is generally not associated with thunderstorms whereas tornadic waterspouts develop in severe thunderstorms.

 

[Greg Stumpf]

Can you locate for us a definition of a "fair weather waterspout"?

Nevermind, I just found one here:

"Fair Weather waterspouts are usually a less dangerous phenomena, but common over South Florida’s coastal waters from late spring to early fall. The term fair weather comes from the fact that this type of waterspout forms during fair and relatively calm weather, often during the early to mid morning and sometimes during the late afternoon. Fair weather waterspouts usually form along dark flat bases of a line of developing cumulus clouds. This type of waterspout is generally not associated with thunderstorms whereas tornadic waterspouts develop in severe thunderstorms. Tornadic waterspouts develop downward in a thunderstorm while a fair weather waterspout begins to develop on the surface of the water and works its way upward. By the time the funnel is visible, a fair weather waterspout is near maturity."

And it is partially incorrect and misleading.

"dark flat bases of a line of developing cumulus clouds" - no, a developing line of cumulonumbis clouds (towering Cu), which is deep moist convection.

"generally not associated with thunderstorms" - deep moist convection does not require lightning. In fact, some tornadic supercells associated with landfalling tropical systems don't contain lightning.

"Tornadic waterspouts develop downward" - uhhhh....no.

 

[Robert Dewey]

I guess there's no point in arguing semantics... My personal opinion is that if the same funnel wouldn't have developed over land simply because of the absents of water, then I would consider that a waterspout. In other words, if water at the surface is the motivating factor in the development and sustenance of the funnel, I consider that a waterspout.

If we have a tornadic thunderstorm that is capable of producing a funnel regardless of terrain (water, vegetation, dust, etc), then I consider that a tornado.

That's my personal thought, as I can't keep up with a semantic argument.

 

[Greg Stumpf]

I guess there's no point in arguing semantics... My personal opinion is that if the same funnel wouldn't have developed over land simply because of the absents of water, then I would consider that a waterspout. In other words, if water at the surface is the motivating factor in the development and sustenance of the funnel, I consider that a waterspout.

But the same process that produces a waterspout also produces a landspout. It has nothing to do with the underlying surface. Where there are waterspouts, the water provides a source of instability. Where there are landspouts, the land provides a source of instability.

Where there are supercell tornadoes, the earth's surface provides instability (could be either land or water). So by the same argument, these should be called different things, which they are not.

We are confident that the process which produces supercell tornadoes and non-supercell tornadoes of the "stretching a vortex on a pre-existing boundary" kind are different, but why call the latter different things based on the surface the vortex is connected to?

They are all tornadoes.

 

[rdale]

I'm no landspout expert - but aren't they connected with some sort of precip? GL waterspouts are dry.

If you push the envelope too far - we'll classify the rare cold air funnel touchdown as a tornado too...

 

[David Wolfson]

I don't think there's much question, Robert, that "cold-air" vorticies are tornados if they otherwise meet the tests, i.e. severe-level circulation at ground-level and driven by cloud-level convection. The western states get a pretty good share of these.

 

[Dan Chaffee]

I'm no landspout expert - but aren't they connected with some sort of precip? GL waterspouts are dry.

Only in that the convective process that under the right circumstnces produces a non-mesocyclone tornado, may or may not be producing precipitation concurrently in and near the same updraft.

Dan Chaffee

 

[scott r currens]

I'm no landspout expert - but aren't they connected with some sort of precip? GL waterspouts are dry.

If you push the envelope too far - we'll classify the rare cold air funnel touchdown as a tornado too...

Many of the tornado warnings (for landspouts) you get in eastern Colorado occur when there is no precip on radar. Like waterspouts they are most common in a cooler post-frontal environment. I seem to have zero ability forecast them so I have givenup on targeting that kind of setup. The non-mesocyclone tornadoes I have observed most often occured on the flanking line of a supercell but not in association with the meso.

Most of the time I here the term "cold air funnel" it is being used to describe a funnel/tornado from a small (mini and/or low-topped) supercell. Is this what you a talking about or something else? I guess I just don't know what a cold air funnel is.

 

[Greg Stumpf]

GL waterspouts are dry.

Perhaps you found the difference between Erie and Ontario spouts!

All of the spouts I witnessed on Lake Ontario were in association with deep moist convection (electrified and not electrified), with rain/snow, and certainly not "dry".

 

[rdale]

Most of the time I here the term "cold air funnel" it is being used to describe a funnel/tornado from a small (mini and/or low-topped) supercell. Is this what you a talking about or something else? I guess I just don't know what a cold air funnel is.

A cold-air funnel is CLEARLY not from a supercell of any variety... It's from a light shower at most, usually just a few sprinkles on a fall day with a very cold-core low and usually northwest flow.

Thanks for the info Greg - I wasn't aware. I can't recall ever dealing with precip during a Toledo area waterspout, and no way was there ever any lightning.

 

[David Draun]

This was a non-supercell tornado/waterspout I witnessed. The funnel dropped from the forward flank of a thunderstorm that was severe-warned for 65mph straight-line winds. It likely developed along a pseudo mini-"triple-point" that developed from the convergence of a southbound OFB, a northbound OFB and the eastbound sea-breeze. This convergence was evident on the KTBW radar shortly before the event. I've never heard of a "fair-weather" waterspout. I have heard of fair weather whirlwinds (water-devils) that can occur over water as well as over land which are NOT pendant from a cumuliform cloud.

About the 6/25 event:

1. This was pendant from a cumuliform cloud with severe weather occuring and numerous CG lightning strikes.

2. A ground circulation was evident on the barrier island as the vortex tracked from Estero Bay over to the GoM. Waterspout, to landspout then back to waterspout again.

With that, it seems that this would be without question, a tornado.