Why Do Tornadoes Form and Head Towards Earth?

[lazyprofessor]

Why does a tornado vortex go down to Earth instead of up to the atmosphere?

Sounds stupid I know, but answer the question if you can.

 

[PaulS1950]

The inward airflow squeezes the point of entry which is at the base.

 

[Andy Resnick]

Why does a tornado vortex go down to Earth instead of up to the atmosphere?

Sounds stupid I know, but answer the question if you can.

Well, you have to remember that a tornado is a very small feature of a stormcloud:

http://www.weatherquesting.com/tornado-cause.htm

There is indeed a funnel of air going up (the mesocyclone)! The tornado funnel cloud itself extends down:

http://library.thinkquest.org/03oct/00758/en/disaster/tornado/formation.html

 

[lazyprofessor]

Again, why does the vortex go to earth?

Let me expand the resources. Explain an eddy and why a whirlpool vortex goes down, not up.

 

[Andy Resnick]

Wow... 'lazyprofessor', indeed. From the second link I posted:

'Next, in order for a tornado to develop, a strong current of cool air must move downward from the back of the storm. This downward current, known as a rear-flank downdraft occurs due to the density of colder air in comparison to warm air, which causes cold air to sink as warm air rises. As the speed of the downdraft increases to speeds up to 100 miles per hour, a tornado forms between the rear-flank downdraft and the updraft.'

Hope that helps...

 

[lazyprofessor]

Yes. And your first link says "We are still puzzling out details. We think tornado development might be related to temperature differences across the edge of the downdraft air (blue arrow) wrapping around the spiraling upward air. But this idea fails sometimes."

Here is a simple thought for you. Take a glass of water and swirl it around and around. Stop. You will see a vortex form if you have been successful in your technique.

Why is there a vortex? Why does it go down into the glass, not from the bottom up?

 

[zeebek]

I am not sure I understand the question. What do you mean by vortex goes down? I may be wrong, but from experience everything in a tornado tends to go up, no?

 

[lazyprofessor]

Let's start over.

A tornado is an example of a vortex. So is a whirlpool.

Both form from the top down. A large "opening" that spirals downward and grows so long as there is sufficient force to keep it moving.

I am asking why the vortex goes down.

A whirlpool appears on the surface of the water then goes down through the water.

A tornado appears on the underside of a cloud and goes down through the air.

I am asking why the vortex "grows" downward.

 

[zeebek]

I cannot answer you question completely but here are the exact statements that I know

1) you use term vortex freely. The reality is that up to now in fluid mechanics there is no clear definition of a vortex
Here is a typical proof, read abstract if you cannot access the full article
http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=282562
The debates continue up to now.

2)

Let's start over.
Both form from the top down. A large "opening" that spirals downward and grows so long as there is sufficient force to keep it moving.

I am not sure you are right here. Read the second theorem
http://en.wikipedia.org/wiki/Helmholtz's_theorems

It means that a vortex tube cannot just start at a point A in a fluid and end at a point B in the fluid. It should be closed. I think that the tornado formation goes all over from the start basically, it is just more visible at the top than near the bottom (earth = wall).

 

[lazyprofessor]

Wow zeebek! You went deep on that one. Nice digging.

I am using the term vortex freely. I am using it in conjunction with various words like tornado, hurricane and whirlpool. They are the visual idea of the "vortex" I am referencing.

I think the "closed" reference in Helmholtz's theorems refers to the circle shape and not the cone shape.

Fill your sink with water. Pull the plug. A vortex will form directly over the drain. While a sink filled with water is not a sky or river, it does give you instant access to a vortex you can watch for yourself.

Why does it form from the top down? Why do you not see the vortex until it appears on top of the water? Is it there before you see it? Or does it take a void for it to occur?

 

[zeebek]

well, I just told you what I know. Some conclusions can be wrong for sure. Meanwhile I just remembered there was a Nature article about whirlpools formation, I always wanted to read it. I will share it by monday, when I will be back to my uni.

 

[Andy Resnick]

Yes. And your first link says "We are still puzzling out details. We think tornado development might be related to temperature differences across the edge of the downdraft air (blue arrow) wrapping around the spiraling upward air. But this idea fails sometimes."

Here is a simple thought for you. Take a glass of water and swirl it around and around. Stop. You will see a vortex form if you have been successful in your technique.

Why is there a vortex? Why does it go down into the glass, not from the bottom up?

Wait... are you asking about tornados or vortex formation in general?

Vortices don't have to be vertical:

http://farm4.static.flickr.com/3103/2617631347_f4f75ea870.jpg

 

[lazyprofessor]

Check this . . .

http://bldgblog.blogspot.com/2010/03/mercedes-benz-tornado.html