Tornado Safety
Adapted from National Weather Service's, "Tornadoes...A Preparedness Guide"

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.

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.

Tornado Variations

• Some tornadoes may form during the early stages of rapidly developing thunderstorms.
• Tornadoes may appear nearly transparent until dust and debris are picked up.
• Occasionally, two or more tornadoes may occur at the same time.

How Do Tornadoes Form?

1. 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.
2. Raising air within the thunderstorm updraft tilts the rotating air from horizontal to vertical.
3. 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.
4. A lower cloud base in an area of rotation known as a rotating wall forms. This area is often nearly rain-free.
5. Moments later a strong tornado develops in this area. Softball-size hail and damaging "straight-line" winds also occurred with this storm.

Tornadoes Can Occur at Any Time of the Year

• In Kansas, peak tornado occurrence is in April through June.
• Tornadoes are most likely to occur between 3 and 9 p.m. but have been known to occur at all hours of the day or night.
• The average tornado moves from southwest to northeast, but tornadoes have been known to move in any direction. The average forward speed is 30 mph but may vary from nearly stationary to 70 mph.

back to top

Shapes and Sizes

Weak Tornadoes -
     - 69% of all tornadoes
     - Less than 5% of tornado deaths
     - Lifetime 1 to 10+ minutes
     - Winds less than 110 mph

Strong Tornadoes -
     - 29% of all tornadoes
     - Nearly 30% of all tornado deaths
     - May last 20 minutes or longer
     - Winds 110 to 205 mph

Violent Tornadoes -
     - Only 2% of all tornadoes
     - 70% of all tornado deaths
     - Lifetime can exceed 1 hour
     - Winds greater than 205 mph

Tornado Myths:

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

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

back to top

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 life-saving warnings to be issued before the tornado forms.

What to Listen for:

When conditions are favorable for severe weather to develop, a severe thunderstorm or tornado WATCH is issued. When a tornado watch is issued, you should remain alert for approaching storms.

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

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 systems to alert communities.

Environmental Clues:

• What to look for...
  • Dark, often greenish skys
  • Large hail
  • Wall cloud
  • Loud roar; similar to a freight train
• Caution...
  • Some tornadoes appear as a visible funnel extending only partially to the ground. Look for signs of debris below the visible funnel.
  • Some tornadoes are clearly visible while others are obscured by rain or nearby low-hanging clouds.
• Other thunderstorm hazards...
  • Flash floods: number ONE weather killer — 146 deaths annually.
  • Lightening: kills 75-100 people each year.
  • Damaging straight-line winds: can reach 140 mph
  • Large hail: can reach the size of grapefruit — causes several hundred million dollars in damage annually to property and crops.

  Back to top

What YOU Can Do:

• Before the storm:
  • Develop a plan for you and your family for home, work, school, and when outdoors.
  • Have frequent drills.
  • Know the county in which you live, and keep a highway map nearby to follow storm movements from weather bulletins.
  • Have a NOAA Weather Radio with a warning alarm tone and battery back-up to receive warnings.
  • Listen to radio and television for information.
  • If planning a trip outdoors, listen to the latest forecasts and take necessary action if threatening weather is possible.
• If a WARNING is issued or if threatening weather approaches:
  • In a home or building, move to a pre-designated shelter, such as a basement.
  • If an underground shelter is not available, move to an interior room or hallway in the lowest floor and get under a sturdy piece of furniture.
  • Stay away from windows.
  • Get out of automobiles.
  • Do not try to outrun a tornado in your car; instead, leave it immediately.
  • If caught outside or in a vehicle, lie flat in a nearby ditch or depression.
  • Mobile homes, even if tied down, offer little protection from tornadoes and should be abandoned.

Occasionally, tornadoes develop so rapidly that advance warning is not possible. Remain alert for signs of an approaching tornado. Flying debris from tornadoes cause 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. The preparedness information on this site, 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.

Back to top