Yellowstone County, Montana
Disaster & Emergency Services
Preparation Tips: High Wind/Tornadoes Contact Department

| What Causes Tornados? | What to listen for | Other Thunderstorm Hazards |
| Before the Tornado | During the Tornado | After the Tornado
| Every School should have a Plan |


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!


Picture of a Tornadoe


What Causes Tornadoes?


Thunderstorms develop in warn, 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.

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 occurring.

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.


Other Thunderstorm Hazards

These dangers often accompany thunderstorms:

  • Flash Floods: number ONE weather killer - 146 deaths annually.
  • Lightning: kills 75-100 people each year.
  • Damaging Straight-line Winds: can reach 140 mph.
  • Large Hail: can reach the size of a grapefruit - causes several hundred million dollars in damage annually to property and crops.

What You Can Do Before the Tornado:

  • Develop a plan for you and your family for home, work, and school.
  • Have emergency supplies on hand during the tornado season.
  • Keep a battery-operated radio, NOAA weather radio, a flashlight, and a supply of fresh batteries in a convenient place.
  • Keep a highway map nearby to follow storm movements from weather bulletins.
  • Know the locations of shelter areas in public facilities. Most schools, public buildings and shopping centers have shelter areas.
  • Make an inventory of your household furnishings and other possessions. Supplement the written inventory with photographs of each room, including furniture, pictures, and valuables. All inventories should be kept in a safe deposit box or some other safe place away from the premises.
  • Listen to radio and television for information and instructions.
  • If planning a trip outdoors, listen to the latest forecasts and take necessary action if threatening weather is possible.

What You Can Do During the Tornado:

  • Take cover immediately if a tornado warning is issued. A tornado warning means that a tornado has been sighted in or near your area.
  • 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, such as a bathroom, closet or hallway on the lowest floor or get under a sturdy piece of furniture.
  • Stay away from windows to avoid flying glass.
  • 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, depression or culvert.
  • Mobile homes, even if tied down, offer little protection from tornadoes and should be abandoned. Seek shelter elsewhere.
  • If a tornado strikes during school hours, teachers should keep children away from windows and seek shelter either in a designated area or in interior hallways. Concerned parents should not attempt to go out in the storm to pick up their children at school.
  • Avoid large, free-span roofs, such as gymnasiums and auditoriums.
  • Have a NOAA Weather Radio with a warning alarm tone and battery back-up to receive warnings.
  • Listen to radio and television for information.

What You Can Do After the Tornado:

  • Be alert for potential hazards. Take extreme care when moving about in an area damaged by a tornado. Be alert for broken power lines, shattered glass, splintered wood, or other sharp protruding objects.
  • If your property is damaged, make temporary repairs to prevent further loss from rain, wind and looting. Keep your receipts -- the costs of temporary repairs may be reimbursable under your insurance policy.
  • Contact your insurance representative as soon as possible. Prompt service usually is available within hours after a tornado or other disaster strikes a community.

Every School Should Have a Plan!

  • Develop a severe weather action plan and have frequent drills.
  • Each school should be inspected and tornado shelter areas designated by a registered engineer or architect. Basements offer the best protection. Schools without basements should use interior rooms and hallways on the lowest floor and away from windows.
  • Those responsible for activating the plan should monitor weather information from NOAA Weather Radio and local radio/television.
  • If the school's alarm system relies on electricity, have a compressed air horn or megaphone to activate the alarm in case of a power failure.
  • Make special provisions for disabled students and those in portable classrooms.
  • Make sure someone knows how to turn off electricity and gas in the event the school is damaged.
  • Keep children at school beyond regular hours if threatening weather is expected. Children are safer at school than in a bus or car. Students should not be sent home early is severe weather is approaching.
  • Lunches or assemblies in large rooms should be delayed is severe weather is anticipated. Gymnasiums, cafeterias, and auditoriums offer no protection from tornado-strength winds.
  • Move students quickly into interior room or hallways on the lowest floor. Have them assume the tornado protection position.

Create a Family Disaster Plan