Tornadoes don’t hop, jump or skip. They can retreat back up into the clouds and spawn again sometime later. They can carve a path through a neighborhood that spares some houses and demolishes others, leaving the impression the tornado skipped houses. While it’s true a tornado can completely destroy one house and minimally damage another right next to it, the reason has nothing to do with jumping or skipping.
It has to do with the internal structure (single or multiple vortex), varying intensity of a tornado and the path the tornado takes. The funnel of a tornado is sometimes composed of two or more vortexes which are just like smaller tornadoes that spin around in a circle. This kind of tornado is called a multiple-vortex tornado and is almost always responsible for narrow paths of extreme destruction. We normally can’t see the individual vortexes because condensation and debris obscure the internal structure and give a tornado that wedge shape appearance.
Even though a tornado can be a hundred yards or greater in width, these smaller vortexes may only be a couple dozen feet in diameter and follow one another, often referred to as “training”. The winds in the vortexes can easily spin in excess of 200 mph and are actually responsible for a majority of a tornado’s destruction.
Since these vortexes are only a couple dozen feet across, they represent a smaller portion of the entire tornado funnel. So as the tornado moves into a neighborhood, almost all the houses will suffer some damage from flying debris and the surrounding winds, but those that get hit by a vortexes will suffer far greater damage compared to those which didn’t. That means one house may be totally destroyed while the house across the street may still be standing and have considerably less damage. This is the main reason why it looks like a tornado may skip over one house while completely destroying the one right next to it.
A large tornado’s destruction can vary significantly in just a quarter mile or so. As an example, one neighborhood might experience destruction consistent with an F3 tornado, but by the time the tornado crosses into the next neighborhood, the intensity might have dropped off considerably down to an F1. By the time it reaches the next neighborhood, it could very well have re-intensified into an F3 or greater. The neighborhood lucky enough to experience F1 strength destruction will suffer far less damage compared the to other areas that experienced the F3 or greater tornado intensity. This may give the appearance that the tornado skipped over a set of houses in one neighborhood while inflicting heavy damage both in front and behind it.
Because of the above reasons, damage reports vary for the same tornado event which make classifying the tornado on the Fujita Scale (the F-Scale) difficult. A new enhanced F-Scale will be implemented starting February 1st, 2007 to address this problem and make tornado reporting more accurate.