Hypothetical tornado/pressure question?

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Is it possible for a tornado to build up enough pressure and sustain a long enough pathline to rip basements out of house as a new damage indicator?

Hi!

Yes, I'm 13, but I've taken the courses and am a certified SKYWARN spotter. I've got an answer to your question.

Tornadoes, even though you've heard of them digging trenches in the ground, normally aren't that quick to extend lower when it reaches a vulnerable basement, which is why you can find protection in your basement. BUT THAT DOES NOT MEAN YOU ARE COMPLETELY SAFE! Even though the tornado itself had not extended into the basement, the actual vortex can still have enough power to lift anything not secured and light enough into the tornado. Heavy things like pool tables and hot water heaters are normally left alone, unless the house is hit by an EF5. In that case, the heater goes for a short flight.

That's absolutely okay that you are only thirteen, you still have the adult knowledge that I obviously need. It is a bit of a weird idea in my head, but I'm just researching it through. I have heard of tornadoes digging trenches into the ground, but I know that most are uncapable of that. I also know that people always refer to wind speed in reference to hypothetical "beyond EF5" tornadoes, but wind speed wouldn't be possible to measure in that instance, only a new damage indicator, and other than completely wiped off the map towns and a very long and wide path line, the only new indicator I can conceive of is the vortex being powerful enough to rip the roof from a basement, eliminating that safety also. Everything else would be immeasurable by our technology.

I don't think so. To rip the basement out of a house it would have to literally blow away the top 8 - 10 feet of soil around the house. That would be considerably more power that any known tornado. Generally tornados do not do much damage to the surface of the ground, except to create a lot of dust, by picking up loose dirt from the surface.

Then again, I guess if the soil around the house was loose enough (like sand or something) and the tornado stayed in one place long enough, it could eventually burrow down to the basement. But thats not really how tornados work. Hurricanes yes, tornados no.

The weapon of destruction is air. The air is being wielded by pressure gradients.

If your goal is to rip open the cieling of the basement of a suburban type house your only weapon is the ambient air in the basement itsself.

Assuming the basment is a living space with a ten foot ceiling its whole length and breadth (like my basement) then you have a ten foot column of air underneath each square foot of ceiling as your weapon to destroy the ceiling.

Ten cubic feet of air wieghs less than one pound. So your asking one pound of air to lift one square feet of the ceiling/flooring between the basement and the first floor.

Even if the first floor, and the whole surrounding outside of the house, suddenly became a vacuum placing maximum suction on the basement air I doubt that one pound of rushing air could do what your asking it to do. You would need extra quantities of air. So the tornado would have to somehow suck air from the outside of the house into the houase and then down into the basement , and then suck the extra heavy air straight up again.

The tornado would have to fight against itsself to do that. Tornadoes are not circus contortionists.

Thank you, because I was having a mental theory between tornadoes and hurricanes, hard to explain, but you gave me the answer.

Hurricanes sometimes move at a walking pace, and even linger over a city ( and beat the crap out of it). But hurricanes dont 'burrow into basements" with wind alone anymore than tornadoes do. They might do that with water, but not with wind alone.

Hence the news reports of people who did die in basements during tornadoes or hurricanes being drowned, not sucked out.

It's possible for a house to collapse on top of a basement during a tornado as well, so you aren't guaranteed safety in one.

Usually what happens in a tornado is flying debris that's been collected in the vortex breaks holes in weak areas of a structure, like windows and doors. Once outside air enters into the house it builds to a higher pressure than the air that's diverted around the house due to the Bernoulli effect. The same force that can help lift a plane into the air can easily pull a house apart. If there's no side opening for air to enter a basement it's relatively protected. Even if the pressure in the center of the tornado itself is extremely low, the basement isn't sealed off from the outside air, so without an additional Bernoulli effect, the pressure will equalize too quickly to allow it to literally suck you out of the ground. What can happen is heavy debris falling into the basement and killing people. Only if the basement was completely sealed off could a tornado suck it out. I don't know how low the pressure would have to get to do that though. It would have to be pretty dang low. I have heard of people's ears being damaged by the sudden drop in pressure though.

I'm wondering why people in Oklahoma don't invest in tornado-proof homes. You could live in a dome-shaped home with armored plates that come down over the windows to prevent debris penetration.

Last edited by marshall on 30 May 2013, 8:08 pm, edited 1 time in total.

We usually don't have the money to move (high poverty state), yet have family ties (especially if you are a registered tribal member). So we sit around and think up ways to rig our house with the money we have against our little brand of natural disaster. Safe rooms are always on the financial wish list here.

Yea, that would be more of an idealistic future solution. It would be nice though since I'm sure people are tired of having to rebuild.

As I understand it you dont even need to puncture the structure.

A big tornado with a vortex big enough to engulf a whole house can cause the whole house to simply explode.

This is because the whole reason a tornado is a tornado is because it is a region of low air pressure. So if a big two story house, with the windows and doors tightly shut, becomes engulfed in a funnel cloud the ambient air inside the house can blow it apart because of the sudden drop in the surroundng air pressure. Houses are built to withstand gravity pulling them down, and wind pushing them over, but not the 'wrong way' stress of air pushing outward. So the house just goes to pieces.


And yes- the tiny amount of air in the basement pushes upward as well. But its pushing up against the whole wieght of the house so it doesnt really do anything. It might warp the cieling/floor a little, and then that collapses when the rest of the debris that was once the house comes crashing down and buries the basement in a big pile.

Not to sound cocky or anything, but weather, tornadoes, and fluid dynamics, are my major area of study and the things you just said are common myths. Homes and even storm shelters are not tightly sealed enough to explode from the low pressure. If the pressure didn't equalize there wouldn't be reports of people's ears popping while inside a tightly closed storm shelter. What causes houses to "explode" is the air entering house and being forced to slow down relative to the air flowing by outside the walls. Also, things like porches and overhanging roofs can act like airplane wings and give the wind "handles" to grab onto and pull a house apart. Another problem is unlike larger buildings, most homes don't have supports that are anchored underground. Many houses simply sit on top of a concrete slab with rather weak fastening. These homes can easily be pushed right off the foundation in an EF4 or EF5 tornado, even if the windows and doors are boarded up and reinforced to prevent air from entering. It's also pretty hard to stop flying debris from puncturing holes which allow air to enter the structure and blow out the roof+walls.

Also, tornadic winds tend to do more damage than winds of similar speed in a hurricane because tornadoes tend to collect and trap lots of debris in their circulation. Two-by-fours and pieces of roof can be carried for miles. All this debris that collects in the vortex greatly increases the destructive power of the wind. Big chunks of debris flying in the wind act like battering rams, smashing through even thick walls. Two-by-fours can even be driven into solid concrete if they're moving fast enough. Even thick dirt, sand, and grit flying through the air enhances the destructive power of the wind. You often see the bark taken off trees due to being sandblasted.