I’m interested in the physics and engineering of this concept … less so the economics.
If money were no object, do we have the technology to build lenticular structures (basically a flat, sprawling dome) that would be impervious to tornados? Giving the high winds nothing to grab on to, as it were.
Ignoring the economics (of space, as well as finance), it isn’t just that tornadoes ‘grab’ things (i.e. the shear forces), there are severe pressure gradients too, but I’m sure it would be possible to design resistant buildings - whether they’d be practical for many purposes is another matter.
Of course we could.
Strong winds aren’t the only probllem. Tornados are accompanied by extreme low atmospheric pressure. Building explode before inside and outstide pressures can equalize.
Sure. We can build aircraft and cars that survive 200mph plus winds so building a house should be no problem. Use enough steel and concrete with aerodynamic surfaces and it should be fairly safe.
Hurricane proof homes should be even easier.
But not many people want to live inside a concrete block.
State of research may have changed since I got my degree in structural engineering but what I recall from school (and visiting the tornado research facility at U of Texas) is that the pressure gradient idea is wrong - buildings are quite porous enough that they don’t “blow up” do to pressure differences.
Tornadoes damage buildings through two basic methods:
High winds blow anything loose off the structure. Loose takes on a different meaning when you’re looking at 200mph+ windspeeds - your roof is “loose”.
High winds fling debris at the structure. A 2x4 at high speeds will blow through barriers like concrete block walls and multiple layers of 3/4" plywood. I’ve seen tests live (using an air cannon to fire “debris”) and it’s very impressive.
As with hurricanes, once the building envelope is penetrated Ma Nature comes in and has quite a party.
When I made the aforementioned visit to Texas (I was working on extreme wind modelling at the time) we talked about wind-resistant structures. There’s nothing really complicated about making a structure “tornado proof”, it’s just not economical and most people don’t want to live in a cement bunker (or deal with construction details like sheathing made of 3" thick plywood).
Here’s one example: http://www.domeofahome.com/
For any structure to be tornado-proof, it just has to be built sturdy enough to withstand damage from anything flung against it and, more importantly, to stand up to the wind load (wind loading is the pressure exerted against an object by the wind; it increases geometrically with the wind speed; sorry I don’t have the formula at hand - it’d be interesting to see what force is exerted against a, say, 12’x40’ wall by a 200 mph wind).
Mythbusters touched on something like this…
My wind engineering books are tucked away in the closet at home but I’ll take a stab at this one.
WARNING - Extreme Back Of Envelope Calculation Follows!
Skydivers hit terminal velocity at ~120mph. Let’s assume that the surface area of my body is about 12 square feet (2x6). At that speed drag force = weight, about 200lbs.
Now let’s scale that up, and ignore differences in Cd due to the fact that I am not shaped like a wall 
F(total) = 200lbs * (480 sq feet/12 sq feet) * (200mph/120mph)^2
= 200lbs * 40 * 2.78
= 22,000lbs or thereabouts.
Call it 11 tons. That’s a lot of force, but a properly braced wall can probably take it.
However, when your neighbor’s car gets shoved through the wall, or your poorly-anchored roof gets peeled off, suddenly that wall isn’t very well braced anymore and you can see why the house will become a heap of construction debris spread across the lawn.
This is true, but I was thinking that a flat dome (think of a giant contact lens)wouldn’t have to be built of necesarily the hardest stuff since (a) the winds couldn’t get a grip on anything, and (b) the flying debris would come in at sub-optimal angles to the “walls/roof” … IOW, everything would be a glancing blow.
Seems like one of the more efficient ways to do it would be to put the entire house on a turntable or a pivot of some sort, balanced on the center, and aerodynamically shaped in a manner similar to a weather vane. High winds pick up, the entire house rotates to point into the wind and provides oblique angles for debris to hit the building at (much easier to deflect a shot comign in at 120 degrees than it is to stop one coming in at 90 degrees).
Now, I don’t want to live in the turntable house, ESPECIALLY once the wind picks up and my living room wall hits me in the face at 30MPH, but the theory is sound (at least, in the mind of this History student who only took one semester of engineering in college 4 years ago). 
I dunno, at this point, you might as well build a hobbit hill and stay clear of the windows once the wind picks up, so as to avoid getting hit by the Gaffer’s goat or his son when things start getting tossed around by the wind. 
I’m with you. The shape you suggest should demonstrate less wind loading, but I hardly know the math for that. And I presume a projectile striking a glancing blow would cause less damage than a direct hit would.
Sorry, but it’s a dreadful idea for several reasons, including:
Yup. One more point is that the projectiles in question range in size from gravel and little bits of debris to things like minivans (I’ve watched video of one being blown around like a toy) and large chunks of concrete (during a post-Andrew damage conference we saw some aerial photos including one of a large concrete roof beam in a field, hundreds of yards away from the building it was blown out of). A “glancing blow” from a two-ton object will be pretty spectacular.
If you are really concerned, build a nice strong home underground
In the words of Ron White: “It’s not that the wind is blowin’. It’s what the wind is blowin’.”
“If you have a Yield Sign in your spleen, it doesn’t matter HOW many pushups you did this mornin!”