National Weather Service Weather Forecast Office

This topic, of course, begs the question: When it comes to a tornadic circulation interacting with an overpass - What is reality? This is an extremely difficult question to answer because it depends on many factors including (but not limited to):

1. the strength of the tornado circulation,
2. the tornado's "angle of attack" on the overpass,
3. the overpass location relative to the path of the center of the tornado circulation,
4. the construction of the overpass (particularly underneath), and
5. the amount and type of debris that has been entrained into the circulation.

To our knowledge, this topic has never been studied scientifically. There have been no modeling studies done regarding the interaction of tornadic winds and an overpass. In the absence of careful scientific and engineering research into this question, no definitive recommendations can be made. There are some widespread misconceptions about this topic, however. These misconceptions are illustrated on the next few slides.