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Tornadoes

 

Although tornadoes occur in many parts of the world, these destructive forces of nature are found most frequently in the United States east of the Rocky Mountains during the spring and summer months. In an average year, 800 tornadoes are reported nationwide, resulting in 80 deaths and over 1,500 injuries. A tornado is defined as a violently rotating column of air extending from a thunderstorm to the ground. The most violent tornadoes are capable of tremendous destruction with wind speeds of 250 mph or more. Damage paths can be in excess of one mile wide and 50 miles long. Once a tornado in Broken Bow, Oklahoma, carried a motel sign 30 miles and dropped it in Arkansas!

What Causes Tornadoes?
Thunderstorms develop in warm, moist air in advance of eastward-moving cold fronts. These thunderstorms often produce large hail, strong winds, and tornadoes. Tornadoes in the winter and early spring are often associated with strong, frontal systems that form in the Central States and move east. Occasionally, large outbreaks of tornadoes occur with this type of weather pattern. Several states may be affected by numerous severe thunderstorms and tornadoes.

During the spring in the Central Plains, thunderstorms frequently develop along a "dryline," which separates very warm, moist air to the east from hot, dry air to the west. Tornado-producing thunderstorms may form as the dryline moves east during the afternoon hours.

Along the front range of the Rocky Mountains, in the Texas panhandle, and in the southern High Plains, thunderstorms frequently form as air near the ground flows "upslope" toward higher terrain. If other favorable conditions exist, these thunderstorms can produce tornadoes.

Tornadoes occasionally accompany tropical storms and hurricanes that move over land. Tornadoes are most common to the right and ahead of the path of the storm center as it comes onshore.

How Do Tornadoes Form?
Before thunderstorms develop, a change in wind direction and an increase in wind speed with increasing height creates an invisible, horizontal spinning effect in the lower atmosphere.

Rising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.

An area of rotation, 2 - 6 miles wide, now extends through much of the storm. Most strong and violent tornadoes form within this area of strong rotation.

Tornadoes Take Many Shapes and Sizes

Weak Tornadoes

Strong Tornadoes

Violent Tornadoes

Tornado Myths:

MYTH: Areas near rivers, lakes and mountains are safe from tornadoes.
FACT: No place is safe from tornadoes. In the late 1980's, a tornado swept through Yellowstone National Park leaving a path of destruction up and down a 10,000 ft. mountain.

MYTH: The low pressure with a tornado causes buildings to "explode" as the tornado passes overhead.
FACT: Violent winds and debris slamming into buildings cause most structural damage.

MYTH: Windows should be opened before a tornado approaches to equalize pressure and minimize damage.
FACT: Opening windows allows damaging winds to enter the structure. Leave the windows alone; instead, immediately go to a safe place.

Weather Radar Watches the Sky
Meteorologists rely on weather radar to provide information on developing storms. The National Weather Service is strategically locating Doppler radars across the country which can detect air movement toward or away from the radar. Early detection of increasing rotation aloft within a thunderstorm can allow lifesaving warnings to be issued before the tornado forms.

Tornadoes can occur at any time of the year

Stay Informed About the Storm
Listen to NOAA Weather Radiio, commercial radio, and television for the latest tornado WATCHES and WARNINGS.

When conditions are favorable for severe weather to develop, a sever thunderstorm or tornado WATCH is issued.

Weather Service personnel use information from weather radar, spotters, and other sources to issue severe thunderstorm and tornado WARNINGS for areas where severe weather is imminent.

Severe thunderstorm warnings are passed to local radio and television stations and are broadcast over local NOAA Weather Radio stations serving the warned areas. These warnings are also relayed to local emergency management and public safety officials who can activate local warning system to alert communities.

What to Listen For...

TORNADO WATCH: Tornadoes are possible in your area. Remain alert for approaching storms.

TORNADO WARNING: A tornado has been sighted or indicated by weather radar. If a tornado warning is issued for your area and the sky becomes threatening, move to your pre-designated place of safety.

SEVERE THUNDERSTORM WATCH: Severe thunderstorms are possible in your area.

SEVERE THUNDERSTORM WARNING: Severe thunderstorms are occuring.

Remember, tornadoes occasionally develop in areas in which a severe thunderstorm watch or warning is in effect. Remain alert to signs of an approaching tornado and seek shelter if threatening conditions exist.

Environmental Clues

Look out for:

Caution:

Other Thunderstorm Hazards

These dangers often accompany thunderstorms:

Tornado Safety

What YOU Can Do

Before the Storm:

If a Warning is issued or if threatening weather approaches:

Occasionally, tornadoes develop so rapidly that advance warning is not possible. Remain alert for signs of a approaching tornado. Flying debris from tornadoes causes most deaths and injuries.

It's Up to YOU!
Each year, many people are killed or seriously injured by tornadoes despite advance warning. Some did not hear the warning while others received the warning but did not believe a tornado would actually affect them. This preparedness information, combined with timely severe weather watches and warnings, could save your life in the event a tornado threatens your area. After you have received the warning or observed threatening skies, YOU must make the decision to seek shelter before the storm arrives. It could be the most important decision you will ever make.

Who's Most At Risk?

Tornado Safety in Schools

EVERY School Should Have a Plan!

Hospitals, nursing homes, and other institutions should develop a similar plan

Your National Weather Service Federal Emergency Management Agency, and American Red Cross educate community officials and the public concerning the dangers posed by tornadoes. YOU can prepare for the possibility of a tornado by learning the safest places to seek shelter when at home, work, school, or outdoors. You should also understand basic weather terms and danger signs related to tornadoes. Your chances of staying safe during a tornado are greater if you have a plan for you and your family, and practice the plan frequently.

Follow these basic steps to develop a family disaster plan...

1. Gather information about hazards. Contact your local National Weather Service office, emergency management or civil defense office, and American Red Cross chapter. Find out what type of disasters could occur and how you should respond. Learn your community's warning signals and evacuation plans.

2. Meet with your family to creat a plan. Discuss the information you have gathered. Pick two places to meet: a spot outside your home for an emergency, such as fire, and a place away from your neighborhood in case you can't return home. Choose an out-of-state friend as your "family check-in contact" for everyone to call if the family gets separated. Discuss what you would do to advise to evacuate.

3. Implement your plan.

A Disaster Supplies Kit Should Include:

4. Practice and maintain your plan. Ask questions to make sure your family remembers meeting places, phone numbers, and safety rules. Conduct drills. Test your smoke detectors monthly and change the batteries at least once a year. Test and recharge your fire extinguisher(s) according to manufacturer's instructionsl. Replace stored water and food every six months.


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