tornados & hurricanes

from what i’ve learned about centrifugal force (maintaining a direction in a straight line away from a central ‘spinning’ point) (try the ball on a string while spinning example), it seems impossible for a tornado or hurricane to exist. what keeps the wind traveling at high velocity in a circular motion instead of using centrifigal force to shear away in straight lines? :confused:

The very low pressure in the center of the hurricane or tornado. It’s like the whirlpool that forms when water is draining out of a bathtub.

i can understand that, but doesn’t that beg to start the chicken or the egg argument? does circulating wind cause a low pressure funnel (and if that is the case - again - why would wind begin to circulate without a low pressure anchor because of centrifugal force) or does a low pressure funnel start wind to circulate?

The pressure is low in the centre, because the air gets heated over the warm ocean and rises rapidly, leaving less air at the surface. Surrounding air rushes in to fill the low pressure and swirls around, just like water going down a plughole. So to answer your question, the low-pressure centre forms first, and causes the wind.

(This is a pretty basic explanation but I believe the basics are right.)

IANA meteorologist, but I’m fairly sure that this is how it works. I would appreciate any corrections.

A hurricane is basicaly one giant thermal updraft. If the earth wasn’t spinning, wind would be drawn directly towards the updraft, and I assume that the system would probably dissipate fairly quickly because different parts of the ocean are warmer than others. Once established though, the cyclone is big enough that Coriolis Force causes the winds to rotate about the updraft in the center. This helps define the shape of the cyclone, and I assume that the rotation averages out the energy in the storm. The winds blowing toward the center pick up heat from the ocean and bring it to the eye, further strengthening the center updraft and, in turn, the storm.

That said, could someone explain the mechanics of how a West African thunderstorm can become a tropical storm after being blown to sea? Are these storms big enough in their own right to become cyclones, or do the have to hit an existing updraft at just the right spot?

Also, what are tornadoes anyway? Are they eddies on the backside of a thunderstorm or other downdraft?

In a rotating object there is a force called the centripetal force directed inwards keeping the object in the rotation. The low pressure in the middle of the hurricane is its centripetal force. The centripetal force for a car going around a turn is the friction of the tires on the raod. The outward centrifugal force is actually a “fictitious force.” However, you could think of it as the centripetal force (inward) overcoming the centrifugal force (outward) if it makes it easier to conceptualize.

Man I hope I spelled all that right.

Almost, but not quite. The same force which acts as a centripetal force in the inertial frame is also the force which acts to counteract the centrifugal force in the rotating frame. But in the rotating frame, that force isn’t a centripetal force, since in the rotating frame, the thing which the centripetal force is acting on isn’t travelling on a curved path.

And there was nothing wrong with the way that talpasca phrased the question. The centrifugal force is no more nor less “fictitious” than gravity, and like gravity, it can be a useful tool in analyzing the dynamics of a situation, so long as one makes sure to use it correctly.