Reader Question

Sorry, couldn't resist the title.

Someone recently asked me how it is that a tornado can damage one house but leave the house next to it with little, if any, damage. From what I know here are the 3 main reasons:

1) Path of the tornado

Often times a tornado is weak enough or small enough to inflict damage on only a very small path. The most intense winds may be only a few yards or even feet wide, leaving one neighbor unscathed and the other neighbor weighted with bad luck. Also, a tornado may not always be fully in contact with the ground, displaying a "hop and skip" pattern.

2) Structural integrity

Small subtleties in the construction of a house can make a big difference. How well is the frame anchored to the foundation? What kind and how good are the clips that are used to attach the roof to the house? One home may display significantly more damage than another because of a small difference in quality of construction. If one small corner of a roof fails and causes the roof to become detached, the rest of the home is left open for the tornado to damage. A house across the street is hit by the same tornado, but the roof remains intact, and thus no interior damage is done......maybe except for a few windows.

3) Multiple-vortex tornadoes

Sometimes several small "suction vortices" will be visible in a tornado (see above image). Sometimes what appears to be one large tornado is actually many smaller vortices, all rotating around each other (hence the name). Oftentimes these can be the most violent tornadoes, and they can also leave striking damage paths. Since the smaller vortices are all rotating every which way, total destruction can lay next to a few shingles peeled off, only a few hundred feet away. The picture below shows a field that was hit by a multiple-vortex tornado. Note all of the smaller paths where the smaller vortices passed.

I hope that answered the question well enough (or maybe too well for some of you!)