What is a tornado and what causes it?

Question

What is a tornado and what causes it?

Answer 1

This question was just dying for a more accurate answer.

A tornado is a funnel of wind that itself has nothing to do with colliding airmasses or a warm front colliding with a cold front, etc, as was mentioned before hand. A warm and cold front colliding doesn't even make sense. But differing airmasses can aid in one's development.

Take an individual thunderstorm. This thunderstorm may be your run-of-the-mill thunderstorm or it may contain components that really juice it up to be extraordinary. Let's use baseball as an analogy, since I adore baseball. A typical thunderstorm is a solo homerun. Now, a solo homerun holds some value, but alone doesn't do a terrible amount of damage. Now, load the bases before that homerun and what will you have? A grand slam, and that does some serious damage. We'll say that a thunderstorm needs its "bases loaded" before becoming severe and possibly a tornadic threat.

An atmospheric condition that can begin to load a thunderstorm's bases is: developing ahead of a cold frontal boundary. Any thunderstorm can develop in an area of general instability with enough heat and moisture- that's a solo home run. But add a cold front into the mix and you have a man on first base. Thunderstorms form out ahead of cold fronts and they can be strong. You know the theory "warm air rises/ cold air sinks"? Picture that actually taking place- a cold front pushes into exceptionally warm (and moist) air with high dewpoints (which occurs ahead of a cold front due to the southerly winds that take place there), and the cold air actually DIGS its way through the warm air, plowing the warm air and making it rise at a faster, almost violent rate. Man, you get some big thunderstorms that way. This often accounts for those severe squall lines most of us experience occasionally, with hail and high winds. And rarely, one or more of these could be tornadic.

The man on second could be described as daytime heating. During max heating, which takes place in the late afternoon hours (after the sun has had a chance to pound on us all say), the extra heat really aids in severe thunderstorm development. So, the sunnier it is in the morning and during the early afternoon, the more of a chance of severe thunderstorms in the late afternoon/evening. Just picture warm air rising at a violent rate, which becomes your "updraft" I will refer to momentarily.

Now, we've talked about the occurences that aid a thunderstorm's lower half, but now it is time to address the upper half of the storm. This is your man on third. Figure that thunderstorms are 30,000-60,000 feet tall - with the severe ones more around the 60,000 ft height, sometimes even taller than that - so, you'd have to figure something must need to take place in the air up there to help make a thunderstorm severe or tornadic. You need some upper level dynamics: Dry air advection at around 10K feet, and the jet stream nearby (high winds aloft allow for extra divergence in the upper levels of the storm, which makes more room for the updrafts of warm moist air to continue coming from below), and these stronger winds aloft can force the updraft to tilt, thus turning the updraft vertical. Importantly, a change in wind direction with height creates turning within the storm. This twisting updraft will stretch, hence increasing its rotation speed (one meteorologist described this as an ice skater spinning faster when she pulls her hands in). This stretching, twisting updraft may touch the ground as the form of a tornado, or stay aloft as a funnel cloud.

As far as "Tornado Alley" goes, the bases are loaded with really big, scary guys with large mustaches and .350 batting averages. In other words, these same things happen in Tornado Alley, but they happen at an extreme, and more frequently (because there are always guys on base). Tornado Alley often has these atmospheric dynamics happening perfectly, and at the same time, because of the location being northwest of the Gulf of Mexico and just east of the Rocky Mountains.

I really hope this made sense. I think I'd have been better off just drawing you a picture.

Answer 2

http://en.wikipedia.org/wiki/Tornado

Surprisingly accurate, according to this meteorologist.

Answer 3

omg wow....

its a large column of swirling winds that is usually caused by two opposing areas of pressure, like a cool front and warm front comming in contact

Answer 4

Simply put, take a low pressure area that would normally cover a huge area.  Now squish it down to a much smaller size.  All that energy concentrated in a relatively small area causes the rotating winds to speed up and you call it a tornado.

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