does a tornado spin clockwise or counterclockwise?

Answer 1

The tornado itself is too small to have its rotation determined by the Coriolis effect. Like water going down plugholes or dust devils, they can spin in either direction at that size.

However, the rotation of a tornado is determined by the rotation of the thunderstorm that spawns it and some thunderstorms are certainly big enough to have their rotation determined by Coriolis. This means that most tornados will spin clockwise in the southern hemisphere and anticlockwise in the north because that is the way the thunderstorms spin.

Answer 2

The large majority of the tornadoes in the northern hemisphere spin counterclockwise (cyclonically), but about 1 in 100 tornadoes spin clockwise. Actually, it has little to do with being in the northern hemisphere, as tornadoes do not last long enough for the effects of Coriolis to impact it. The actual cause is somewhat more complex...involving how vertical wind shear (change of wind speed/direction with height) is "converted" into rotation within the updraft of a thunderstorm. Consider how a football spins after it is thrown horizontally, then take the football and have it spin about a vertical axis...that's what the air in a rotating updraft is doing.
Most of the time, the result is counterclockwise rotation within the updraft.

For more information on tornadoes and other deadly weather, how they form, and how to utilize real-time Internet data to anticipate and recognize such hazards, I refer you to a public education course I've developed...for more information, go to http://www.stom-prep.com. Hope this helps...

Answer 3

Tornadoes typically come from supercell thunderstorms that formed when a vortex in the horizontal direction is tilted into the vertical and split into two counter-rotating vortices. These can each become supercell thunderstorms with opposite rotation and either one can make a tornado. However, in the US at least the growth of the clockwise rotating supercell is inhibited by the presence of the counterclockwise rotating supercell, since it is usally blocking the flow of moist air from the south that fuels both storms. Occasionally the clockwise rotating cell thrives and a clockwise spinning tornado can form. I don't know that extensive studies have been done on this elsewhere.

Answer 4

Most tornadoes rotate counterclockwise in the N hemisphere, but not all. That is because the storms themselves, specifically the mesocyclones, rotate counterclockwise.

The most most common explanation for a clockwise, or anticyclonic, tornado, is that it occurs in a supercell's flanking line just southwest of the parent storm's mesocylone. There the parent storm's rear flank downdraft can spin a flanking line updraft clockwise.

Another scenario involves supercells that split in two, where the left-splitting mesocyclone *may* rotate clockwise.

edit: I agree with most of what tentofield said, as I usually do, but I think he could have stated what he "meant" better. No individual tornadic thunderstorm, and what I really mean by that is a mesocyclone, is large enough, nor has a duration long enough, to get its rotational direction from the Coriolis.

Storms are the result of synoptic (large) scale atmospheric parameters, and it is those synoptic parameters that are influenced by the Coriolis. In turn, the synoptic parameters, such as the counterclockwise rotation of upper level troughs and surface lows, causes individual mesocyclones to also (usually) rotate counterclockwise.

Brief explanation of that: Because of surface friction, lower level winds are slower than upper level. S or SE'ly low level winds are sheared over by stronger S or SW'ly winds above them, and a horizontal vortex begins rotating W to E at its top/E to W at the surface. (If you visualize this, it is rotating clockwise as you look northward... horizontally, as the stronger winds at about 2000 to 5000 feet make the vortex spin "over the top".)

When an updraft pulls that vortex into the vertical, the developing storm thus rotates counterclockwise. That may seem counterintuitive, but a cyclonic (counterclockwise) storm rotation is as viewed from above, or from space. When you were first visualizing the horizontal vortex, you were visualizing it from the ground, and then upwards; i.e. from the other direction.

Answer 5

At least the great majority of tornadoes rotate counterclockwise (as do all low-pressure systems) in the northern hemisphere, and clockwise in the southern hemisphere, for the reason (coriolis force) given by Eric Peterson in response #1. But occasionally, it would seem, northern hemisphere tornadoes do rotate clockwise: S. Flora's book "Tornadoes of the United States" cites an 1890 article in the American Meteorological Journal. Its author, a J.P. Finley, states that, of 550 American tornadoes he studied, 29 were deemed to have rotated clockwise. I have not been able to find any "modern" study of this question. But I believe it could be true. The region of swirling air that contracts to become the tornado is not itself large enough in extent to have its rotation dictated by the coriolis force; rather, it "inherits" this tendency from the great masses of air whose movement sets the stage for the storms and any associated tornadoes. If the study cited is correct and representative, on occasion the direction of rotation is set by some other factor, perhaps the topography in the area where the tornado forms,
for example.

Answer 6

The great majority of tornadoes rotate counterclockwise
(as do all low-pressure systems) in the northern hemisphere, and clockwise in the southern hemisphere, for the reason (coriolis force) given by Eric Peterson in response #1. But occasionally, it would seem, northern hemisphere tornadoes do rotate clockwise: S. Flora's book "Tornadoes of the United States" cites an 1890 article in the American Meteorological Journal. Its author, a J.P. Finley, states that, of 550 American tornadoes he studied, 29 were deemed to have rotated clockwise. I have not been able to find any "modern" study of this question. But I believe it could be true. The region of swirling air that contracts to become the tornado is not itself large enough in extent to have its rotation dictated by the coriolis force; rather, it "inherits" this tendency from the great masses of air whose movement sets the stage for the storms and any associated tornadoes.

P.S. I am not sure i understand a word of this but it should be logical a scientist from Stanford wrote this.

Answer 7

In the Northern Hemisphere it spins counter-clockwise except on rare occasions an anti-cyclone tornado develops and spins clockwise.

In the Southern Hemisphere it spins clockwise except on rare occasions an anti-cyclone tornado develops and spins counter-clockwise

Answer 8

Tornadoes normally rotate cyclonically in direction (counterclockwise in the northern hemisphere, clockwise in the southern).

Check this out,
http://en.wikipedia.org/wiki/Tornado

Answer 9

95% of the tornadoes spin counter clockwise, but there those 5% that do just the opposite, this is only in the Northern Hemisphere, in the Southern Hemisphere it's just the opposite.

Answer 10

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I just saw a stormchaser special on the Discovery channel last night. In the Northern Hemisphere they go clockwise, in the Southern they go counter-clockwise. However(and they actually showed one and mentioned how rare they are) there are instances of tornadoes turning opposite to the norm...it has to do with wind direction when it is forming...And they did say it is really rare for it to happen.