Can Tornadoes Strike In River Valleys?

[KevanGuy]

That logic disregards some very basic ideas. It ignores the likely possibility that rivers, ridges, and valleys have little or no effect on mature tornadoes. Tornadoes have passed seemingly unaffected over mountain ridges 3,000 feet high. Dozens have crossed the Mississippi River, from Minnesota to Louisiana. Both sides of the river, at the confluence of the Mississippi and Missouri Rivers, near St. Louis, have seen devastating tornadoes.

Topography may have some influence, but protection is not one of them. Weak tornadoes may damage hilltops. But well-formed, mature tornadoes may actually stretch themselves into valleys and intensify. During this vortex stretching, the funnel diameter may shrink in diameter and the tornado will spin even more rapidly. This is hardly what one would call protection for buildings in a valley.

http://www.tornadoproject.com/myths/myths.htm

[Kerplunk]

According to this pretty animation on CNN:

http://edition.cnn.com/interactive/w...ado.animation/
Other reference:
http://en.wikipedia.org/wiki/Tornado

According to the pretty pictures, a tornado is primarily formed by, a) a big updraft forcing warm air up, b) instability at higher points causing a rotation in the clouds, c) cold air cycling back to ground level causing the funnel to form.

I assume that while the conditions to form a tornado can be present anywhere, the chance of them being in some places is rather low. It might be that some valleys cannot heat up the air fast enough to recycle the cooler air, or produce the updraft needed to start one.

Both sources also say that a tornado doesn't have to visible, but because of the air/dirt it usually is. It's possible that a tornado can go over a lake without being seen.

Might be some interesting links in the wiki there to see how and where these things forms.

[Hemi-Cuda]

Originally Posted by KevanGuy

The power and energy behind a tornado (or more specifically the supercell that would spawn it) superceedes anything a river valley could throw at it.

what about mountains? growing up in the Okanagan Valley i've never heard of a tornado hitting anywhere in there. in fact that area seemed unlikely to be hit by any kind of natural disaster. apart from some small floods i can remember as a kid due to large snow melt i've never heard of anything big happening there weatherwise

[KevanGuy]

From the NOAA:

Tornado Myth: Areas near rivers, lakes, and mountains are safe from tornadoes.

FACT: No place is completely safe from tornadoes. Tornadoes can happen anywhere regardless of terrain. In the late 1980s, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000 ft. mountain. (NOAA/NWS)

[Hemi-Cuda]

Originally Posted by KevanGuy

From the NOAA:

Tornado Myth: Areas near rivers, lakes, and mountains are safe from tornadoes.

FACT: No place is completely safe from tornadoes. Tornadoes can happen anywhere regardless of terrain. In the late 1980s, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000 ft. mountain. (NOAA/NWS)

hmm, i wonder why flat areas are always more susceptible to them then. there has to be something geographical that explains why tornado valley receives so many more than somewhere in the rockies

[KevanGuy]

Originally Posted by Hemi-Cuda

hmm, i wonder why flat areas are always more susceptible to them then. there has to be something geographical that explains why tornado valley receives so many more than somewhere in the rockies

Tornado Alley you mean? They get more cause it is basically the line where (generally speaking) cold air from the north meets warm air from the south.

You dont get tornado spawning conditions around mountains very often but, if you do, a tornado will spawn. Also, there is more flat ground around. That is also a reason why you see more there.