Tornado FAQs

From NOAA & NOAA's National Severe Storms Laboratory:
A SEVERE WEATHER PRIMER:
Questions and Answers about TORNADOES

Where do tornadoes come from?

Tornadoes come from the energy released in a thunderstorm. As powerful as they are, tornadoes account for only a tiny fraction of the energy in a thunderstorm. What makes them dangerous is that their energy is concentrated in a small area, perhaps only a hundred yards across. Not all tornadoes are the same, of course, and science does not yet completely understand how part of a thunderstorm's energy sometimes gets focused into something as small as a tornado.

How fast can a tornado go?

We're not really sure what the highest wind speed might be inside a tornado. Since strong and violent tornadoes destroy weather instruments, we really only have measurements of the winds inside weaker tornadoes. Mobile Doppler radars can measure wind speeds in a tornado above ground level -- and the strongest was 318 mph measured on May 3, 1999 near Bridge Creek/Moore, Oklahoma.

What are the people called who study tornadoes?

People who study tornadoes are just research meteorologists. You may have heard another term - storm chaser - but that really refers to people who chase tornadoes for a hobby. Research meteorologists do science. They have to come up with questions they think they can answer by taking certain measurements.

How fast do tornadoes move?

We don't have detailed statistics about this. Movement can range from almost stationary to more than 60 mph. A typical tornado travels at around 10-20 miles per hour.

How long is a tornado usually on the ground?

Detailed statistics about the time a tornado is on the ground are not available. This time can range from an instant to several hours. The average is about five minutes.

Does NSSL do things like they showed in the movie "Twister"?

The movie Twister was based upon work NSSL did in the mid-1980s using a 55-gallon drum outfitted with various meteorological sensors. It was called TOTO (TOtable Tornado Observatory). NSSL tried for several years to put it in the path of an oncoming tornado, but had minimal success. It did not have the sensors that fly up into the tornado, like in the movie. However, that is not a bad idea and with all the advances being made in computer technology, we might be able to do that someday.

What direction do tornadoes spin?

Most tornadoes (but not all) in the Northern Hemisphere spin counterclockwise.

Where do tornadoes occur?

Whenever and wherever conditions are right, tornadoes are possible, but they are most common in the central plains of North America, east of the Rocky Mountains and west of the Appalachian Mountains. They occur mostly during the spring and summer; the tornado season comes early in the south and later in the north because spring comes later in the year as one moves northward. They usually occur during the late afternoon and early evening. However, they have been known to occur in every state in the United States, on any day of the year, and at any hour. They also occur in many other parts of the world, including Australia, Europe, Africa, Asia, and South America. If you'd like to plot tornado tracks, download Severe Plot and the associated data from the NOAA Storm Prediction Center.

Has every state had a tornado?

Yes, although some states have many more tornadoes than others.

Are there tornadoes in the Arctic Circle?

We are not aware of any tornadoes occurring in the Arctic Circle. Tornadoes need moisture and warm air to form, which is unusual at that lattitude. Plus tornadoes or their evidence have to be observed by someone, and the Arctic Circle has few residents!

Do tornadoes really stay away from gullies, rivers and mountains?

A gully could actually make a tornado more intense, just as an ice skater spins faster when he or she stands up tall and stretches their arms up straight over their heads. Every major river east of the Rockies has been crossed by a significant tornado, and high elevations in the Appalachians, Rockies, and Sierra Nevada have all experienced tornadoes. A violent tornado crossed the Continental Divide in Yellowstone National Park.

Where is Tornado Alley?

"Tornado Alley" is a just a nickname made up by the media for an area of relatively high tornado occurrence - it is not a clearly defined area. Is tornado alley the area with the most violent tornadoes, or is it the area with the most tornado related deaths, or the highest frequency or tornadoes? It depends on what kind of information you want!

How many tornadoes hit the US each year?

About 1000.

Where is the most common "birthplace" for a violent tornado?

According to research done by Dr. Harold Brooks here at NSSL, the most common birthplace for a violent tornado (F4 or greater) is in south-central Oklahoma.

I want to chase tornadoes on my vacation – what time of year and what locations are best?

Check NSSL's Severe Weather Climatology page.