Why aren't tornadoes invisible if they are just circulating air/wind?

Question

Why aren't tornadoes invisible if they are just circulating air/wind?

Answer 1

It's all the c**p IN the tornado that makes it visible.  They're often not visible until they "touch down" and start picking up material.  Rain, water, dust, plant parts, building material, cats and dogs.....etc, etc.

Answer 2

Because of all the dust and debris they carry.

Answer 3

Some videos of tornadoes forming show just that - the circulatory air flow is not very visible until the tornado sucks in dirt and debris from the ground.

Answer 4

As stated above.  

They are clouds, full of rain, debris, and everything it picks up as it travels.

Answer 5

it isnt just air/wind...dirt, dust, wood, metal, etc...all that is picked up with the tornado.

Answer 6

cuz of the dust

Answer 7

Because they are a low pressure system, they cause a condensation cloud, which is what you generally see.

Answer 8

Because they are not just circulating air and wind.  They contain moisture (ie - clouds or mist), dust, and debris.