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Old 10-03-2005, 11:39   #1
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Tornado

We had a Tornado here in NZ yesterday. We had a nasty but common weather pattern pass over us yesterday and a small West Coast Town in the South Island got a Tornado out of it. It came in off the Sea and ran right through the town. Not sure what the population is, I would imagine a few thousand. Certainly ain't big. It demolished buildings and houses in it's path. Luckily and surprisingly when you see the damage, no one was killed and only three with minor injuries.
Actually, Tornadoes at Sea (water spouts) are seen off our NZ shores more often than many realise.

Can someone answer this. I was wondering if the spinning effect of a Tornado has any bearing on latitude. I.E, you see bigger Tornadoes in The USA because Tornado ally is closer to the equator, when compared to the smaller ones we see here, cause we are much further from the equator. I realise the storm itself has the biggest bearing, but the spinning effect must be determined by the speed of rotaion of the Earth, would it not???
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Old 10-03-2005, 13:16   #2
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Shear vs Coriolis

The severe thunderstorms which produce tornadoes form where cold dry polar air meets warm moist tropical air. This is most common in a section of the United States called Tornado Alley. Also, the atmosphere needs to be very unstable. An unstable atmosphere is one where the temperature decreases rapidly with height. Atmospheric instability can also occur when dry air overlays moist air near the earth's surface. Scientists believe a vertical wind sheer (wind that changes direction with height) causes the tornado to begin spinning. Most tornadoes spin cyclonically, but a few spin anticyclonically. Because there are records of anticyclonic tornadoes, itís not likely that the Coriolis Effect (or distance from the equator) causes the rotations.

Thereís more to Tornados than I can relate. See:
Tornado Formation ~ by B. Geerts and E. Linacre
http://www-das.uwyo.edu/~geerts/cwx/...nado_form.html

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Old 10-03-2005, 14:10   #3
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Tornado

I can recall seeing water spouts and mini wirly gigs in NZ. Fortunatley not many folks live on the wet coast of the South Island not unlike the left wet coast of Vancouver Island.
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