Space & Innovation

Extreme Tornado Outbreaks Becoming More Common

Swarms of twisters that last for days are on the rise. Continue reading →

Scientists aren't sure why, but tornado outbreaks - large-scale weather events that last for one to three days and span across big regions - seem to be getting bigger, with more twisters on average.

Worse yet, we're also seeing increased changes of having extreme outbreaks - such as the April 25-28, 2011 "Super Outbreak" that generated 305 tornadoes over an area stretching from New York to Texas, and included three massive tornadoes that rated F5, the highest category on the Enhanced Fujita Scale. That catastrophe killed nearly 350 people and caused an estimated $11 billion in property damage.

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Those scary findings are in an study published recently in Nature Communications, in which Columbia University researchers looked at data going back to 1954.

The researchers found that the average number of tornadoes in an outbreak has increased by 50 percent, from 10 to 15. If there's any good news, it's that the number of tornadoes rated F1 and higher on the Fujita - the ones capable of causing substantial property damage - isn't rising.

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The study's authors said in a press release that they're not sure what exactly is driving the increases.

"The science is still open," said lead author Michael Tippett, a climate and weather researcher at Columbia University's School of Applied Science and Engineering and Columbia's Data Science Institute. "It could be global warming, but our usual tools, the observational record and computer models, are not up to the task of answering this question yet."

Tippett said that many scientists expect the frequency of atmospheric conditions favorable to tornadoes to increase in a warmer climate - but even today, the right conditions don't guarantee a tornado will occur "When it comes to tornadoes, almost everything terrible that happens, happens in outbreaks," Tippett explained. "If outbreaks contain more tornadoes on average, then the likelihood they'll cause damage somewhere increases."

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The study was co-authored by Joel Cohen, director of the Laboratory of Populations, which is based jointly at Rockefeller University and Columbia's Earth Institute.

Despite the longer-term pattern, the past several years have seem reduced numbers of tornadoes in the United States, according to the National Oceanic and Atmospheric Administration. The agency received about 1,000 reports of tornadoes in 2015, compared with 1,625 in 2011, one of the most violent and deadly tornado years on record. The deadliest single event in 2015 was a tornado in northern Mississippi on Dec. 23 that killed nine people.

An extreme tornado outbreak in late April 2011 caused massive damage in Alabama and elsewhere, and killed nearly 350 people.

The winners are in from the National Oceanic and Atmospheric Administration's "Weather in Focus" photo contest, picked from more than 2,000 entries taken between Jan. 1, 2014 and March 31, 2015. "From rainbows and sunsets to lightning and tornadoes, the winning photos aren’t just captivating to look at, but inspire us to look at the world in different ways," said Douglas Hilderbrand, NOAA's contest judge and Weather-Ready Nation Ambassador Lead. "It was difficult to pick winners from so many good entries." In first place, from the category "Science in Action," is "Green Bank Telescope in WV" by Mike Zorger, Falls Church, Va.

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All 16 winning images will be displayed in a

Gateway to NOAA

exhibit located on the NOAA campus in Silver Spring, Md., starting in July. Second place in "Science in Action" went to "Photographer captures the aurora" by Christopher Morse, Fairbanks, Alaska.

In third place: "Atmospheric Research Observatory" by Joseph Phillips, Boulder, Colo.

Photo: NASA's Extreme Weather Photo Contest

And honorable mention also went to Joseph Phillips, Boulder, Colo. for "Atmospheric Research Observatory."

In the category "Weather, Water & Climate," first place went to "Snow Express" by Conrad Stenftenagel, Saint Anthony, Ind.

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In second place was "Proton arc over Lake Superior" by Ken William, Clio, Mich.

"With a Bang" by Bob Larson, Prescott, Ariz., won third place in the "Weather, Water & Climate" category.

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Honorable mention went to Alana Peterson, Maple Lake, Minn. for "Raindrops on a Leaf."

A second honorable mention was won for "Fire in the Sky over Glacier National Park" by Sashikanth Chintla, North Brunswick, N.J.

Sunsets and Other Sky Wonders

In the category "In the Moment," first place went to "Smoky Mountains" by Elijah Burris, Canton, N.C.

Second place went to "Spring Captured: Freezing rain attempts to halt spring" by Mike Shelby, Elkridge, Md.

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And third place went to "Rolling clouds in Lake Tahoe" by Christopher LeBoa, San Leandro, Calif.

Of course the professionals had their own category. First place was won by Brad Goddard, Orion, Ill., for "Stars behind the storm."

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Brad Goddard pretty much cleaned up this category, winning second (and third) place with "A tornado churns up dust in sunset light near Traer, IA."

Third place went for "A tornado crosses the path, Reinbeck, IA" by Brad Goddard.

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“Fog rolls in from the ocean on a hot summer day, Belbar, N.J.” by Robert Raia, Toms River, N.J., won honorable mention in the pro category.

To see all of the images on NOAA's website, go here.