Tornadoes have been known to strip asphalt pavement, and even scrape the ground with their winds, but we don't know if they can actually dig into the ground.

The deadliest US tornado was in 1925 on March 18. It is called the "Tri-state" tornado and killed 695 people along its 219 mile track through Missouri, Illinois and Indiana.

Not that we know of yet...but the thunderstorms that produce tornadoes release energy that builds up in the atmosphere.

On the average tornadoes kill about 60 people each year, mostly from flying or falling debris.

The very center of the tornado is probably almost calm, but may have some downward motion in it. There have not been any direct measurements of the winds because the instruments used to measure wind speed can't survive long enough to measure the eye.

The most common and practical way to determine the strength of a tornado is to look at the damage it caused. From the damage, we can estimate wind speeds. Professor Theodore Fujita developed a scale to help us evaluate damage and classify tornadoes. In summary, the Fujita Scale ranges from F0-F5. F0 tornadoes have winds of 40-72 mph and can break branches off of trees and damage signs. F5 tornadoes have winds from 261-318 mph, which can lift houses off foundations, and make automobiles as dangerous as a missile flying through the air.

An "Enhanced Fujita Scale" will be implemented by the National Weather Service by February, 2007. In a nutshell, the enhanced F scale was developed to rate tornadoes in a more consistent and accurate manner. It will still rate tornado categories from F0 to F5, but the ranges of wind speed in each category are now more accurate. It takes into account more variables than the original scale did when assigning a wind speed rating to a tornado, incorporating 28 damage indicators such as building type, structures, and trees. For each damage indicator, there are 8 degrees of damage ranging from the beginning of visible damage to complete destruction of the damage indicator. The original F scale did not take these details into account. Go to: www.spc.noaa.gov/faq/tornado/ef-scale.html

Dr. Ted Fujita, the inventor of the "F-scale", did plot hypothetical winds at an "F6" level. But, it was untested theory and therefore he was making educated guesses. The F-scale is based on damage to man-made structures, not precise wind speeds. Scientists have very few measurements of tornado winds. F5 is the most intense possible damage level - total destruction. Fujita said that although he speculated that a tornado could be stronger than an F5, even a structural engineer could not distinguish F6 damage from F5. F5 is the highest scientifically accepted rating for tornadoes. The highest recorded windspeed in a tornado was 318 mph, still within the bounds of the F5 description. These precise wind speed numbers are actually educated guesses and have never been scientifically verified. As we obtain more measurements on tornadoes, we may actually learn that the wind estimates on the Fujita scale are wrong! Damage can vary from place to place or even building to building based on construction, even if the wind speeds were the same.

The damage from tornadoes comes from the strong winds they contain. It is generally believed that tornadic wind speeds can be as high as 300 mph in the most violent tornadoes. Wind speeds that high can cause automobiles to become airborne, rip ordinary homes to shreds, and turn broken glass and other debris into lethal missiles. The biggest threat to living creatures (including humans) from tornadoes is from flying debris and from being tossed about in the wind. It used to be believed that the low pressure in a tornado contributed to the damage by making buildings "explode" but this is no longer believed to be true.

While it may appear tornadoes target mobile home parks, they actually do not. An F1 tornado might do significant damage to a mobile home, and cause minor damage to a site built home -- looking like the tornado "skipped" the house. Mobile homes are, in general, much easier for a tornado to damage and destroy than well-built houses and office buildings. A mobile home, or manufactured home, by definition, is built at a factory and taken to the place they will occupy--so they are much more affordable than a house built on-site. Also, they are often built with lighter-weight materials, which do not hold up well in tornadic winds.

Straight-line winds can also destroy a mobile home as easily as a tornado, especially one that is not anchored. Any wind gust that is sustained for 3 seconds over 50mph can cause damage to mobile homes.

Some states are beginning to require storm shelters for their residents. The statistics definitely support this – 7% of our population lives in mobile homes, and almost half of tornado fatalities in the U.S. occur in mobile homes. The problem of warning and sheltering mobile home residents has become the biggest obstacle to continuing to reduce death tolls from tornadoes.

Absolutely not! Stopping under a bridge to take shelter from a tornado is a very dangerous idea, for several reasons:

1. Deadly flying debris can still be blasted into the spaces between bridge and grade – and severely injure any people taking shelter there.
2. Even when strongly gripping the girders (if they exist), people may be blown loose, out from under the bridge and into the open – possibly well up into the tornado itself. Chances for survival are not good if that happens.
3. The bridge itself may fail, peeling apart and creating large flying objects, or even collapsing down onto people underneath. The structural integrity of many bridges in tornado winds is unknown – even for those that may look sturdy.
4. Whether or not the tornado hits, parking on traffic lanes is illegal and dangerous to yourself and others. It creates a potentially deadly hazard for others, who may plow into your vehicle at full highway speeds in the rain, hail, and/or dust. Also, it can trap people in the storm's path against their will, or block emergency vehicles from saving lives.