United States Search and Rescue Task Force

Thunderstorms

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The key ingredient that defines a thunderstorm is lightning.   Since lightning creates thunder, a storm with lightning is called a thunderstorm.

Thunderstorms occur when large air masses rise quickly into the atmosphere, forming huge cumulonimbus clouds.  Severe air currents inside the clouds cause water droplets and ice crystals to crash into one another continually, and the friction between these particles creates static electricity in the cloud.  Over time, opposite charges build between the top and bottom of the cloud, and the bottom of the cloud and the earth.  When these opposing charges become intense, a gigantic spark occurs (lightning) which jumps the gap between the cloud and the earth.  The thunder accompanying lightning is the noise produced by the discharge.

What is Lightning?

In recent years, people have been killed by lightning while:

Drawing of a lightning boltboating
Drawing of a lightning boltstanding under a tree
Drawing of a lightning boltplaying soccer
Drawing of a lightning boltswimming
Drawing of a lightning boltriding on a lawnmower
Drawing of a lightning boltfishing in a boat
Drawing of a lightning boltgolfing
Drawing of a lightning bolt talking on the telephone
Drawing of a lightning bolt mountain climbing
Drawing of a lightning boltbike riding
Drawing of a lightning boltloading a truck

Which way does lightning travel?

A cloud-to-ground lightning strike begins as an invisible channel of electrically charged air moving from the cloud toward the ground. When one channel nears an object on the ground, a powerful surge of electricity from the ground moves upward to the cloud and produces the visible lightning strike!

Lightning Myths and Facts

Some thunderstorms can be seen approaching, while others hit without warning. It is important to learn and recognize the danger signs and to plan ahead.

BEFORE

Learn the thunderstorm danger signs

Have disaster supplies on hand

Check for hazards in the yard.
Dead or rotting trees and branches can fall during a severe thunderstorm and cause injury and damage.

Make sure that all family members know how to respond after a thunderstorm.
Teach family members how and when to turn off gas, electricity and water.

Teach children how and when to call 9-1-1, police, fire department, and which radio station to tune for emergency information.

Severe Thunderstorm Watches and Warnings:


A severe thunderstorm watch is issued by the National Weather Service when the weather conditions are such that a severe thunderstorm (damaging winds 58 miles per hour or more, or hail three-fourths of an inch in diameter or greater) is likely to develop. This is the time to locate a safe place in the home and tell family members to watch the sky and listen to the radio or television for more information.

A severe thunderstorm warning is issued when a severe thunderstorm has been sighted or indicated by weather radar. At this point, the danger is very serious and everyone should go to a safe place, turn on a battery-operated radio or television, and wait for the "all clear" by the authorities.

Learn how to respond to a tornado and flash flood.
Tornadoes are spawned by thunderstorms and flash flooding can occur with thunderstorms. When a "severe thunderstorm warning" is issued, review what actions to take under a "tornado warning" or a "flash flood warning."

Develop an emergency communication plan.
In case family members are separated from one another during a thunderstorm (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together.

Ask an out-of-state relative or friend to serve as the "family contact". After a disaster, it's often easier to call long distance. Make sure everyone knows the name, address, and phone number of the contact person.

Contact you local emergency management office or American Red Cross chapter for more information on thunderstorms and lightning.

DURING

If indoors:

If outdoors:

If in a car:

Estimating the Distance from a Thunderstorm:


Because light travels much faster than sound, lightning flashes can be seen long before the resulting thunder is heard. Estimate the number of miles you are from a thunderstorm by counting the number of seconds between a flash of lightning and the next clap of thunder. Divide this number by five.

Important: You are in danger from lightning if you can hear thunder. Knowing how far away a storm is does not mean that you're in danger only when the storm is overhead.

Hail:
Hail is produced by many strong thunderstorms. Hail can be smaller than a pea or as large as a softball and can be very destructive to plants and crops. In a hailstorm, take cover immediately. Pets and livestock are particularly vulnerable to hail, so bring animals into a shelter.

AFTER

Check for injuries:
A person who has been struck by lightning does not carry an electrical charge that can shock other people. If the victim is burned, provide first aid and call emergency medical assistance immediately. Look for burns where lightning entered and exited the body. If the strike cause the victim's heart and breathing to stop, give cardiopulmonary resuscitation (CPR) until medical professionals arrive and take over.

Remember to help your neighbors who may require special assistance--infants, elderly people, and people with disabilities.

Report downed utility wires.

Drive only if necessary. Debris and washed-out roads may make driving dangerous.

Mitigation:
Mitigation includes any activities that prevent an emergency, reduce the chance of an emergency happening, or lessen the damaging effects of unavoidable emergencies. Investing in preventive mitigation steps now, such as installing lightning rods to carry the electrical charge of lightning bolts safely to the ground or purchasing flood insurance, will help reduce the impact of severe thunderstorms in the future.

 

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