- The U.S. experiences about 80% to 90% of all of the tornadoes that occur across the world.
- About 1,200 tornadoes hit the U.S. each year, the National Severe Storms Laboratory said.
- Tornadoes are rated from EF-0 (light damage) to EF-5 (incredible damage) based on a list of damage indicators.
Tornadoes, which can be among the most violent phenomena of all atmospheric storms on Earth, are most common in the United States. In fact, each year, “the U.S. experiences about 80% to 90% of all of the tornadoes that occur across the world,” said Randy Cerveny, a professor of geography at Arizona State University.
About 1,200 tornadoes hit the U.S. each year, the National Severe Storms Laboratory said.
Tornadoes are capable of completely destroying well-made structures, uprooting trees and hurling objects through the air like deadly missiles, the National Weather Service said.
What is a tornado?
A tornado is “a narrow, violently rotating column of air that extends from a thunderstorm to the ground,” according to the National Severe Storms Laboratory in Norman, Oklahoma. But because wind is invisible, it is hard to see a tornado unless it forms a funnel made up of water droplets, dust and debris.
While the wording of definitions may vary, there is one constant: In order for a phenomena to be classified as a tornado, it must must be in contact with the ground and a thunderstorm cloud at the same time, the Storm Prediction Center said.
If there is no ground contact, it’s simply known as a funnel cloud.
When is tornado season?
Tornadoes can and do happen at any time of the year, experts say.
However, the peak tornado season for the southern Plains (Texas, Oklahoma and Kansas) is from May into early June, NOAA said. And along the Gulf Coast, it is earlier in the spring. In the northern Plains and upper Midwest (North and South Dakota, Nebraska, Iowa and Minnesota), tornado season is in June or July.
Overall, there is a general northward shift in tornado season in the U.S. from late winter through midsummer.
Tornadoes can also happen at any time of day or night, but most tornadoes occur from 4–9 p.m.
What causes a tornado? And how are tornadoes formed?
According to the Storm Prediction Center, the classic answer – “warm moist Gulf air meets cold Canadian air and dry air from the Rockies” – is a gross oversimplification. Most thunderstorms that form under those conditions never make tornadoes.
“The truth is that we don’t fully understand,” the National Severe Storms Laboratory said. “The most destructive tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone.” Supercells can also produce damaging hail, severe non-tornadic winds, frequent lightning and flash floods.
How do you prepare for a tornado?
As the National Weather Service says, be “weather-aware” by having a smartphone or NOAA weather radio at the ready to receive alerts about impending dangerous weather. You should also have a family plan that includes an emergency meeting place and related information. If you live in a mobile home or home without a basement, identify a nearby safe building you can get to quickly, such as a church or the home of a family member.
What should I do during a tornado? How do I survive a tornado?
If you are at home during a tornado warning, go to your basement, safe room or an interior room away from windows. If you’re outside, seek shelter inside a sturdy building immediately if a tornado is approaching.
If you’re in a vehicle, the best course of action is to drive to the closest shelter. If you are unable to make it to a safe shelter, either get down in your car and cover your head or abandon your car and seek shelter in a low-lying area such as a ditch or ravine.
What is the Enhanced Fujita scale? What are the different categories of a tornado?
The Enhanced Fujita scale, named after legendary tornado researcher Ted Fujita, is a scale that measures the strength of a tornado based on the damage it caused. Unlike hurricanes, which are based on the wind speed of a storm as it progresses, tornadoes are only rated after they’ve roared through a region.
Tornadoes are rated from EF-0 (light damage) to EF-5 (incredible damage) based on a list of damage indicators and degrees of damage, which help estimate the range of wind speeds the tornado likely produced, the National Weather Service said.
What’s the difference between a tornado watch and a tornado warning?
A tornado watch means weather conditions are ripe for tornadoes to form. A warning means one has been spotted or indicated on radar.
Watches are issued by the Storm Prediction Center for counties where tornadoes may occur. The watch area is typically large, covering numerous counties or even states.
Warnings, which are issued by local Weather Service offices, typically encompass a much smaller area (around the size of a city or small county) that may be impacted by a tornado identified by a forecaster on radar or by a trained spotter or law enforcement official who is watching the storm.
There is also a relatively new category: A tornado emergency is reserved for what the weather service considers “exceedingly rare” situations when a severe threat to human life and catastrophic damage from a tornado are imminent or ongoing.
Ideally people in these areas have already gathered in safer places. Visual confirmation from reliable sources or indication of a tornado from radar imagery is also required for a tornado emergency warning.
What is a tornado watch?
A “tornado watch” means that you should remain vigilant, but not yet take action, the National Weather Service reports.
The directive is meant to signal that a tornado is possible in or near the “watch area,” which is typically fairly large, encompassing a number of counties or states. If your home is in the designated area, make sure to check supplies and be ready to act fast should a tornado warning be issued.
Is a tornado watch or warning worse?
A “tornado warning” is more severe than a tornado watch, according to the National Weather Service.
A tornado warning means there is confirmation that a tornado has been spotted in your area or detected by weather radar and there is “imminent danger to life and property.” The NWS offers these tips:
- Move to an interior room on the lowest floor of a sturdy building.
- Avoid windows.
- If you are in a mobile home, vehicle, or outdoors, move to the closest substantial shelter to protect from flying debris.
While a “tornado watch” usually covers a large swath of land, a “tornado warning” is more targeted, often pinpointing a city or county that is in danger.