Gateway Arch and tornado?

[Stan_Shmenge]

Fox news was just showing the Gateway Arch in St. Lois and mentioning tornados. I am sure a tornado would rip the arch to shreds, so what are they depending on? What about downtown areas in tornado alley in general? Could a tornado cut a swath through downtown Kansas City destroying skyscrapers and such? So why has this never happened? Are we just playing the odds? :eek:

A related question- Are the North American plains the only place on earth where tornados occur in frequency?

[Scruloose]

Here’s a column Cecil did on tornados and cities.

From the column:

In addition, however, there is some indication that larger cities tend to be tornado-resistant, at least in the sense that they get fewer twisters than would seem statistically likely.

I have been communing on this topic with Theodore Fujita, a professor of meteorology at the University of Chicago and one of the world’s leading authorities on tornadoes. He says a big city can whittle down the intensity of a tornado by one or two levels on the “Fujita scale” (and guess who THAT’s named after).

Thus an F0 (40-72 MPH winds, light damage) or F1 (73-112 MPH, moderate damage) tornado might be reduced to a mere thunderstorm upon encountering a town of consequence.

Professor Fujita thinks there are a couple reasons for this. One is that big cities contain steel or reinforced-concrete high-rise structures that can withstand tornado-strength winds, and these slow the twister down by sheer force of friction.

The warm updrafts that cities create also tend to interfere with tornado formation somehow.

Professor Fujita’s reasoning on this is a bit difficult to follow–they don’t call this guy “Mr. Tornado” for nothing–but in general we can say that tornadoes need an inrush of cool air at ground level, which cities do not provide.

And on St. Louis specifically:

You may recall the sad tale of Kalamazoo, Michigan, much of which was reduced to ruins by tornadoes a few years ago. Going further back, the city of St. Louis has suffered some of the worst tornado disasters in history, including one in 1896 that killed 306 people, and another in 1927 that killed 79.

[brianjedi]

Downtown Nashville got hit by a couple of tornadoes a few years ago. Blew out a bunch of windows and damaged several buildings, so it’s not completely unheard of for it to happen.

The reason it doesn’t happen often, I’ve heard from science teachers, is that the canyons formed by tall buildings, coupled with the heat that the concrete and asphalt retains keeps tornadoes from maintaining wind speed.

The Arch was built to deflect only 18" in 150 mph wind (source: http://www.nps.gov/jeff/ar-facts.htm ) so a tornado would have to be very strong and right on top of the Arch to do a lot of damage.

[Scruloose]

I almost forgot…

In 1997, the wife and I were driving from Wisconsin to my new duty station in Miami. The day before we arrived, we awoke in our motel somewhere in Georgia and this picture was on the front page of the USA Today newspaper.

:eek:

A Google image search of “Miami tornado” returns some great pics.