Just a theory here

[Drew.Gardonia]

might be far fetched, but just want to see hear some opinions on this.

most tornadoes when they rotate create a vacuum, by turning in an upward barber shop stick style spiral.

I was on the back deck the other day just thinking to myself,

why can't/don't tornadoes turn in a downward barber shop stick spiral direction, and instead of creating a vacuum, it creates a blower...so instead of the tornado lifting everything straight up, it would just blow everything straight down into the ground?

(i know some tornadoes turn the opposite direction, but they still have the upward lift that creates the suction? right?)

Is this possible? Could a change in say the Earth's magnetic field, potentially cause this at some point down the road? Or could we just have a really freak tornado, that basically has it's medula oblongotta (sorry took that line from The Waterboy) all messed up?

If it happened, would it be more intense than a normal tornado? More dangerous? Higher winds? more extreme winds? More destructive?

I know there's microbursts, and down drafts, but for the purposes of this discussion let's leave them out of it, and pretend they don't exist, and discuss what I've stated above.

I'm interested in hearing the replies from more experienced weather gurus.

 

[Jeff Snyder]

Andrew,

Upward acceleration of parcels below the level of maximum buoyancy results in (assuming mass conservation) convergence in the low-levels. This is a fancy way of saying that as air accelerates upward through the low-levels of an updraft, there is convergence at or below cloud base. This convergence results in increased vertical vorticity, or "spin" about the vertical axis (see the first term on the right-hand side of the top equation HERE); this increased "spin" helps intensify mesocyclones and may have some role in the development of tornadoes (there's much more to it, see as how the greatest convergence into the thunderstorm updraft does not occur immediately above ground level -- it's better to say that it may have some role in the development of low-level mesocyclones). If you were to have descent through a storm, you would see divergence near the surface, which will, by itself, destroy vertical vorticity and weaken the rotation. In fact, you sometimes do see some descent (i.e. sinking motion) along the periphery of a tornado funnel as it decays. In terms of air parcels converging into and beneath the updraft, you can use the conservation of angular momentum by thinking of a figure skater pulling her/his arms inward resulting an a faster spin.

The nonlinear dynamic term of the diagnostic pressure perturbation equation says that rotation is associated with a negative perturbation pressure; vortices such as tornadoes have a negative perturbation pressure (i.e. a pressure deficit relative to the surroundings) as a result of its rotation. The fact that tornadoes are essentially centers of low pressure helps explain the vacuum-like nature of tornadoes (i.e. air accelerates in towards the tornado). As noted above, thunderstorm updrafts themselves act like giant vacuums as a result of convergence under and at cloud base. You can (and do) sometimes get vortex breakdown and an axial downdraft within the center of the tornado that results in a two-celled vortex. In such tornadoes, instead of the air near the surface spiraling radially into the tornado and rapidly turning upward near the axis of the tornado (i.e. the corner flow region), the tornado will actually be characterized by a downdraft in the center, with the primary "updraft" of the tornado shaped like a cylinder at some distance away from the center of the rotation.

 

[Wes Carter]

Andrew,

I see you are in Murfreesboro, TN and still looking for your first tornado. I think that your first tornado almost found you a couple of months ago!

The reason that tornadoes 'suck' is because they form in the updraft region of the storm, usually in the rain-free base. In the downdraft region of the storm the air is basically falling to replace the air that has gone up via the updraft. This air has little potential energy other than it's higher density so there is little acceleration other than gravitational acceleration.

The air rising in the updraft region has a great ally called the latent heat of vaporization that actually causes it to accelerate upward when the CAPE values are high enough and the cap erodes. Couple this with some decent helicity and you can get a tornado in the updraft region of a supercell thunderstorm.

I am still learning myself so there are others here who can explain things much better than I can.

BTW, I live close to the Boro so PM me if you might be interested in chasing sometime in the area.

 

[Bob Hartig]

Tornadoes have nothing to do with the earth's magnetic field, Andrew. They're a product of atmospheric instability, moisture, and wind shear. While every tornado is unique, those basic components remain the same. Tornadoes spin upwards for the same reason that their parent convective storms develop upwards rather than from the top down: because heat rises through a cooler environment.

I recommend that you pick up Tim Vasquez's The Storm Chasing Handbook and familiarize yourself with the fundamentals of convective weather. You'll gain plenty of valuable insights into what makes tornadoes tick.

 

[Drew.Gardonia]

Andrew,

I see you are in Murfreesboro, TN and still looking for your first tornado. I think that your first tornado almost found you a couple of months ago!

The reason that tornadoes 'suck' is because they form in the updraft region of the storm, usually in the rain-free base. In the downdraft region of the storm the air is basically falling to replace the air that has gone up via the updraft. This air has little potential energy other than it's higher density so there is little acceleration other than gravitational acceleration.

The air rising in the updraft region has a great ally called the latent heat of vaporization that actually causes it to accelerate upward when the CAPE values are high enough and the cap erodes. Couple this with some decent helicity and you can get a tornado in the updraft region of a supercell thunderstorm.

I am still learning myself so there are others here who can explain things much better than I can.

BTW, I live close to the Boro so PM me if you might be interested in chasing sometime in the area.

sounds good Wes thanks for the invite! I will send you a pm shortly.

Tornadoes have nothing to do with the earth's magnetic field, Andrew. They're a product of atmospheric instability, moisture, and wind shear. While every tornado is unique, those basic components remain the same. Tornadoes spin upwards for the same reason that their parent convective storms develop upwards rather than from the top down: because heat rises through a cooler environment.

I recommend that you pick up Tim Vasquez's The Storm Chasing Handbook and familiarize yourself with the fundamentals of convective weather. You'll gain plenty of valuable insights into what makes tornadoes tick.

Oh I realize that Bob, I was just curious in theory, if a tornado could ever form and spin downwards, and if it ever did happened why it would happen?

just speaking theoretically (more like thoughtful imagination), that's all.