Tornadoes are narrow rotating columns of air and can be the most violent of all atmospheric storms. The most powerful tornadoes can cause injury, loss of life, widespread damage, and the complete destruction of homes.
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Tornadoes are spinning columns of air that can stretch from the ground to the clouds. Although most are weak, they can be extremely powerful, deadly, and cause significant damage. There are two main types of tornadoes based on the type of thunderstorm they are associated with--supercell and non-supercell. Supercell thunderstorms are the only thunderstorms that contain a consistent rotating updraft known as a mesocyclone. Supercell tornadoes are the most common and are usually more dangerous. Non-supercell tornadoes are weaker, shorter-lived, and include land and water spouts.
The US averages over 1,200 tornadoes each year--by far the country with the highest number. Canada is a distant second, with about 100 tornadoes per year. Although tornadoes have been reported in all 50 U.S. states, most occur from the Gulf Coast through the southern plains up through the midwest and northern plains to North Dakota and Minnesota. Three regions in the U.S. have disproportionately high numbers of tornadoes--the southern plains which are nicknamed “Tornado Alley,” the Gulf Coast referred to as “Dixie Alley,” and Florida. The states with the highest number of tornadoes per year, ranging from about 140 to 50, are Texas, Kansas, Florida, Oklahoma, and Nebraska. Although Texas has the highest number of tornadoes per year, Alabama averages the highest number of tornado-related mortalities with about 14 deaths per year. The rolling topography and more extensive forest cover in Alabama appears to make it more difficult to see tornadoes coming and as a result, reduces the amount of time to find shelter. Because tornadoes gain their energy from thunderstorms that normally form in the afternoon and evening; most tornadoes also form in the afternoon and early evening hours. Tornadoes are more frequent in the southern plains in late spring and occasionally early fall. Along the gulf coast and Florida, they are more common in late fall. The damage, injuries, and loss of life from tornadoes can be catastrophic. The 2019 tornado season claimed 41 lives, injured hundreds, and caused an estimated $7.1 billion in damage.
Tornadoes are classified into five categories using the Enhanced Fujita (EF) Scale based on wind speed and damage estimates. The scale uses observed levels of damage to 28 different indicators including homes, automobiles, power lines, and trees. In the U.S. About 77% of all tornadoes are considered weak (EF0-EF1) and about 95% are below EF3. Although most tornadoes are weak, on average in the U.S. there are over 50 EF3 and EF4 and nearly one EF5 tornado per year. On average, tornadoes result in about 71 deaths per year in the U.S.
Enhanced Fujita Scale#
|EF0||65-85 mph||Light Damage|
|EF1||86-110 mph||Moderate Damage|
|EF2||111-135 mph||Considerable Damage|
|EF3||136-165 mph||Severe Damage|
|EF4||166-200 mph||Devastating Damage|
|EF5||>200 mph||Incredible Damage|
You and Tornadoes#
Health and Safety#
Meteorologists at NOAA’s Storm Prediction Center issue daily forecasts for organized severe thunderstorms and monitor areas they think are at high risk for tornadoes. When conditions are favorable for tornadoes they issue a severe thunderstorm or tornado watch. When a severe thunderstorm or tornado has been spotted or detected by radar, then the National Weather Service issues a Severe Thunderstorm or Tornado Warning. Watches and warnings are available through alert services (such as from AreaHub) and/or local media outlets.
If a severe thunderstorm or tornado watch has been issued, then stay alert and monitor local media for additional information--a watch is intended to give you time to prepare and review your safety plan. If you see a Tornado or a Tornado Warning is issued in your area, you should seek appropriate shelter immediately and follow the sheltering recommendations below.
NOAA National Weather Service Tornado Shelter Recommendations#
|Permanent Structure with a Basement||Move to the lowest level basement and put as many walls between yourself and the outside as possible.|
|Permanent Structure without a Basement||Move to an interior hallway or room.|
|Mobile Home||Extremely dangerous even if anchored to the ground. Leave immediately and find shelter in a permanent structure.|
|Vehicle||Vehicles are extremely risky in a tornado. Leave the vehicle and shelter in a permanent structure. If it is possible to do it safely, then drive out of the path of the tornado. As a last resort, park the vehicle out of traffic lanes and remain in the vehicle with seatbelts on.|
|In the Open Outdoors||If it is not possible to find shelter in a permanent structure, then get as far away from trees and vehicles as possible as they can be blown onto you, lie face-down and flat on the ground, and use your arms to protect the back of your head.|
In general, long-term property values in regions like tornado alley that are known for a higher frequency of tornadoes, are not affected by tornadoes. When tornadoes cause damage in a community, there is often a short-term increase in home values as demand increases for temporary housing. Over the long term, it is also possible for overall home values in a neighborhood to increase if damaged homes in the neighborhood are rebuilt better than before. According to research from Austin College, the addition of a safe room can increase the value of a home by about 3.5%.
What You Can Do#
Keep track of tornado and severe thunderstorm forecasts from the National Weather Service, follow sheltering recommendations if a tornado is spotted or a Tornado Warning is issued, and be prepared with an emergency supply kit. The Centers for Disease Control (CDC) recommends an emergency kit with water, non-perishable food, medication, fresh batteries, a battery-operated device to listen to the latest emergency weather information, and a list of important information including telephone numbers.
Safe rooms are hardened structures within a home or building that provide near-absolute protection from extreme weather events including tornadoes. If you are building or buying a home in a region where tornadoes consistently occur, then constructing a safe room or purchasing a home with a safe room is worth considering. The Federal Emergency Management Agency (FEMA) has provided hazard mitigation funding to eligible states that is available for residential safe room construction. Contact your State Hazard Mitigation Officer for information about this process including design requirements and funding eligibility.
Most standard homeowner’s insurance policies provide coverage for wind damage caused by tornadoes. In some cases and regions, there are exclusions, especially related to wind and water damage. Review your homeowner’s policy to find out which home damages are covered.
AreaHub’s Knowledge Center is updated regularly and provides information drawing upon scientific studies and sources.
- NOAA The National Severe Storms Laboratory: “Severe Weather 101: Tornadoes.”
- NOAA: “The Enhanced Fujita Scale.”
- NOAA: “Supercell Thunderstorms.”
- NOAA: “U.S. Tornado Climatology.”
- NOAA: “Tornado Safety.”
- Centers for Disease Control: “Staying Safe in a Tornado.”
- FEMA: “Safe Rooms.”
- FEMA: “Hazard Mitigation Assistance Grants.”
- Insurance Information Institute: “Tornadoes and Insurance.”
- Construction Management and Economics: “Tornado Shelters and the Housing Market.”
- NOAA National Centers for Environmental Information: “U.S. Tornado Climatology.”