If you are familiar at all with children's nonfiction, then you are probably familiar with the name Seymour Simon.
If you are familiar at all with young boys (especially my 11yo), you are probably familiar with their affinity towards tornadoes, as well as any other suitably destructive natural disaster.
We had the 1999 version of this title at one time, but it has been weeded (probably for both age and condition), so I can't compare to see exactly what has been updated. Simon's name has long been associated with accuracy, however, and as usual the information is presented in a straightforward yet engaging style. Personally I would have updated more photographs - the images tend towards grainy, which may be off-putting for some readers, and there are so many newer/sharper images available.
It's easy to understand the fascination with tornadoes - they are really nothing but air, and yet they can wipe out entire towns. I grew up in Ohio, where tornado drills were a part of the school year, and I have witnessed their destruction firsthand. Even Christopher, who lives in an area that never actually gets tornadoes, expresses fear about them. One of the best ways to conquer a fear, however, is to learn more about it, so I will definitely be taking this home soon. A solid addition to an elementary library, although it may not be the first to catch a reader's eye.