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Supercharged

clouds

How to:

tell how close a storm is

Ice crystals and water droplets are tossed around in storm clouds, building up static electricity.

■■El

This charges up the entire cloud like a giant battery, with the positive charge at the top and the negative charge at the bottom. It also creates a positive charge on the ground below the cloud.

01 ■ When you see the lightning flash, start counting. Use a stopwatch if you have one, or just count, “thousand-and-one, thousand-and-two, thousand-and-three . .

In a 6-mile (10-km) high cloud, the difference between the positive and negative charges can build up to 100 million volts!

Divide the number of seconds by five to give the distance in miles, or by three to give kilometers. So, if you count 15 seconds, the strike was 3 miles (5 km) away.

Eventually, the huge voltage overcomes the electrical resistance of the air, and the electricity in the cloud flashes to the ground as lightning.

03,

If you can’t hear any thunder at all, the strike was probably morę than 10 miles (16 km) away. If you don’t get time to count, watch out!

WE1RD OR WHAT?

Fipctrical storms can ° than the split-seccrf teshes^

normal lightning, mwe a

making hissmg noises, anu ^m vanish or explode!

Lightning

. A lightning strike begins with a faint, branched “leader"

that zigzags down from the cloud toward the ground.

16 million

S

A really big storm cloud can contain an amazing

250.000    tons

of water—that’s the weight of

1.000    jumbo jets!

B

The number of thunderstorms that break out worldwide every year

100

The number of lightning strikes, worldwide, every second

3,000 to 1

The odds against being struck by lightning in your lifetime

1,200

The number of tornadoes reported in the United States each year

695

The number of people killed by the most deadly tornado in history—the Tri-state Twister that hit Missouri, Illinois, and Indiana on March 18, 1925

. When this makes contact— y^^ usually with a high point such as a tree—the main discharge shoots back up the leader with a much brighter flash.

^ Within a fraction of a second, the massive voltage heats

the air along the path of the lightning strike to an incredibly high temperaturę.

. The intense heat makes air in the strike path expand explosively, causing the crackling shock wave that we cali thunder.

Dorling Kindersley. All REights Reserved.    .