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Lightning, Thunder, and Tornadoes
Introduction

Sean and Michael McQuilken in a strong electric field just prior to lightning.

It is hard to imagine anybody failing to be impressed by the beauty--as well as the danger-brought about by a thunderstorm. Spectacular though they may be, such storms are not rare. In fact, they are common throughout the world and occur about 40,000 times each day. Although their frequency varies greatly from place to place, virtually every location on Earth is vulnerable to thunder and lightning from time to time.

Lightning can create inconveniences--such as blowing out all the electrical appliances in a house. It can also do considerable damage, such as starting forest fires. And, of course, it can kill: during an average year, about 200 people are killed by lightning in the United States and Canada. But considering that the population of these two countries approaches 300 million people, it is easy to see that your chances of being struck are extremely remote.

Yet people do get hit by lightning. Consider the experience of the McQuilken family on their trip to Sequoia National Park, California, in August 1975. As the sky began to darken, Sean, Michael, and their sister Mary noticed their hair standing on end. Recognizing the apparent comedy of the situation, the boys posed for the photograph shown in Figure 11-1. Hail followed almost immediately. Then lightning struck--literally--and Sean was knocked unconscious. Michael quickly administered artificial respiration, which probably saved Sean's life. Another victim was less fortunate, however. The lightning had apparently forked off, with another branch hitting two nearby people, one of whom was killed.

But the effects of lightning and thunder are eclipsed by an even greater menace--tornadoes. We will now examine how, where, and why violent weather occurs, and we'll look at the situations that cause some storms to be weak and others to become destructive and deadly.



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