Large tornadoes can be weak, and small tornadoes can be violent. This tornado is pictured on the right side of the slipcase, shown here . Notice the debris in the air. Eyewitnesses to this tornado claim to have seen as many as 6 vehicles in the air at the same time when it passed over a parking lot. Another consideration is the stage in the life cycle of the tornado.
Large tornadoes can also be strong and small tornadoes can be weak.
The Fujita Scale is based on damage , not the appearance of the funnel. Storm spotters, storm chasers and other weather observers often try to estimate the intensity of a tornado when they are in the field, basing their judgement on the rotational speed and amount of debris being generated as well as the width. However, the official estimate is made after the tornado has passed. Personnel from the National Weather Service office that issued the warning survey the site to determine the F-Scale rating. Sometimes they call in experts from out of the area.