This week’s continued spring weather preparedness focus is on tornadoes.
Each year, more than 1,200 tornadoes take place in the United States. These destructive and awe-inspiring events are notoriously difficult to predict. Yet, NOAA and others are deepening our understanding of tornadoes and improving warning times to save lives. The resources in this collection cover the past, present, and future of tornado science and forecasting. Through research and technical advances, we can now better predict and prepare for these once unknowable phenomena.
Tornadoes usually only last a few minutes. However, some of these rapidly rotating columns of air can potentially last more than an hour and travel dozens of miles. Most of the worlds tornadoes occur in the United States, and they are most common between April and June.
Tornado formation
There are multiple types of tornadoes. Tornadoes come from mainly two types of thunderstorms: supercell and non-supercell. Non-supercell tornadoes include landspouts and waterspouts.
Supercell tornadoes
Most tornadoes result from supercell thunderstorms. You can often recognize supercell thunderstorms by their anvil-shaped cumulonimbus clouds. These thunderstorms have a strong, rotating, and persistent updraft that can reach speeds of 100 mph (approximately 161 km/hour). This means there is a strong column of rotating air within the storm.
The rotating updraft in these storms may begin because of wind shear. Wind shear is a change in wind direction or speed with height. So, the wind may be blowing in a different direction and speed near the ground than the wind higher up.
Once the rotating updraft is established, rotation near the surface can start strengthening and organizing, which can lead to a tornado. Most people think of tornadoes as the funnel cloud, or condensation funnel, stretching from sky to land. But a tornado can form and be in touch with the ground even without a visible condensation funnel.
Non-supercell tornadoes
Though most tornadoes form from supercell thunderstorms, there are other tornado types as well. Strong lines of thunderstorms, referred to as quasi-linear convective systems, also called squall lines, can cause tornadoes to form.
Landspouts and waterspouts are also types of tornadoes. They can form during thunderstorm formation, rather than from a supercell storm that is already rotating strongly. Note that dust devils are different from landspouts, and although dust devils can be damaging, they are not a type of tornado.
Non-supercell tornadoes are typically weaker than supercell tornadoes, but they can still be dangerous and destructive.
Scientists still have unanswered questions about tornadoes: Why do most supercell thunderstorms not result in a tornado? How exactly do tornadoes form? What are the causes of wind shear that lead to rotation? NOAA scientists are working to learn more about tornado formation and improve forecasting. Read more in the Tornado research and advancements in forecasting section.
Tornado prediction and detection
Even though meteorologists cannot predict exactly when and where a tornado will occur, they use what they know about tornado formation to make lifesaving predictions.
Forecasters and storm spotters are trained to recognize thunderstorm features that make tornado formation more likely. Storm spotters are community members that are formally trained to recognize certain conditions and report them to the National Weather Service. Forecasters are trained professionals with degrees focused on meteorology or atmospheric science. They look for conditions that could lead to tornadoes using weather observations and tools like computer models. These models analyze data from multiple sources, including Doppler radar, weather balloons, satellites, and more.
When forecasters detect conditions that have become favorable for severe weather, the National Weather Services Storm Prediction Center can put out a tornado watch. If a tornado is imminent or ongoing, they put out warnings based on the path of the storm. When a tornado warning is issued in your area, you may:
- Get an emergency alert to your phone.
- Hear tornado sirens blaring in your community.
- Hear an announcement on local television and radio stations, or if you have one, on your NOAA Weather Radio.
Tornado research and advancements in forecasting
Did you know that before 1950, the U.S. government was banned from mentioning tornadoes in forecasts in the U.S. for fear that it would cause panic? Tornado research has come a long way since then. NOAA has made great strides and is always working to increase our understanding of tornadoes and improve forecasting and forecast delivery.
Be weather-wise: Reducing the risks
Knowing what to do during severe weather is key to reducing your risk should a tornado form. Though we summarize safety advice below, if you live in an area where tornadoes form, we suggest visiting the ready.gov tornado web page.
- Your first line of defense is to be aware of weather forecasts, warnings, and watches.
- Its best to seek shelter during thunderstorms, whether or not it could produce tornadoes. Remember: When thunder roars, go indoors.
- Once you are aware of a watch or warning, make sure you know where to go, whether youre at home, work, school, or out and about. Plan ahead thinking of your safe place where you can seek shelter should a tornado approach.
- This may be a specially designed room like a storm shelter or safe room. Or it may mean identifying the safest locations in a nearby building.
- The safest location in a building is the most interior room on the lowest floor. Ideally, it should be a sturdy interior room without windows that is below ground, if possible, or at ground level.
- If you live in a mobile home or home without a basement, identify a nearby safe building you can get to quickly.
- If you are stuck outside and cannot reach somewhere indoors, lie flat in a ditch, ravine, or low spot in the ground.
- No matter where you are, protect your head with your hands and any other protective objects you have handy, such as a coat, book or pillow.
As always, keep an eye on the sky and be safe when outdoors.
Bob the EM
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