Who knew? Colorado, a twister haven
June 26, 2013
Colorado tornado facts since 1950
Top months for tornadoes
Top five tornados for injuries
May 22, 2008: 78 injuries, one fatality, Windsor
June 3, 1981: 42 injuries, Thornton
June 6, 1990: 14 injuries, Limon
Oct. 17, 1971: 9 injuries, Wray
March 28, 2007: 9 injuries, 2 fatalities, Holly
Top cluster of tornadoes
Within three minutes at around 7:25 p.m., on May 28, 2001, three different tornados hit El Paso County, injuring a total of 13 people, (two injured four people, and one injured five people)
Top five counties for tornadoes
Kit Carson: 93
Top five years for tornados
Top five tornadoes in miles traveled
May 22, 2008: Windsor — 38.7 miles
June 18, 1951: Crowley and Otero counties — 29.9 miles
March 28, 2007: Prowers and Kiowa counties (Holly) — 28 miles
Sept. 18, 1986: Morgan County — 25 miles
June 9, 1990: Larimer and Weld counties — 23 miles
May 17, 1962: Baca County — 23 miles
Top five widest tornados
May 22, 2008: Windsor — 1,760 yards
June 17, 1953: Conejos County — 1,417 yards
July 5, 2000: Logan County — 1,320 yards
June 9, 2001: Lincoln County — 1,320 yards
May 5, 1996: Washington County — 1,320 yards
Most destructive (property damage) since 1996
$147 million: Windsor — May 22, 2008
$8 million: El Paso County — May 28, 2001 (two others occurred at the same time in El Paso that caused a total of $120,000 in damage)
$6 million: Arapahoe County — Aug. 29, 2002
$4.01 million: Prowers and Kiowa counties (Holly) — March 28, 2007
$4 million: Lincoln County — May 31, 1999
Before 1996, there were three tornados that caused between $5 million and $50 million in damages
June 6, 1990: Limon
June 15, 1988: Denver
June 6, 1981: Thornton
8 other tornadoes caused between $500,000 and $5 million in property damage.
Time of the day tornadoes are most likely
72 — Midnight to noon
161 — 12:01 to 2 p.m.
192 — 2:01 to 3 p.m.
294 — 3:01 p.m. and 4 p.m.
264 — 4:01 p.m. and 5 p.m.
270 — 5:01 p.m. and 6 p.m.
235 — 6:01 p.m. and 7 p.m.
191 — 7:01 p.m. and 8 p.m.
132 — 8:01 p.m. and 9 p.m.
136 — 9:01 p.m. and 11:59 p.m.
Source: An I-News analysis of 63 years of tornado data kept by the National Weather Service
The tornado sighting that set off alarms and frightened passengers at Denver International Airport Tuesday afternoon was a startling reminder that Colorado is indeed twister country.
Since 1950, only six other states have experienced more tornadoes than the 1,948 documented here, an I-News examination of federal weather data found.
And two of the state's fastest-growing counties — Weld and Adams, which surrounds DIA — had the most tornadoes during that 63-year span. Combined, they accounted for 410 tornadoes, more than one of every five. In addition, the Weld County town of Windsor experienced the most destructive twister in state history.
Then there's the airport sitting on the high plains 25 miles from downtown Denver. On an average day, DIA sees about 145,000 passengers, and at any given time as many as 20,000 people may be in the terminal and concourses. Officials there are keenly aware that the airport could become a tornado bull's-eye at any given time.
Two separate tabletop exercises conducted earlier this year for just such an eventuality became showtime reality Tuesday.
"We followed protocol and everything went very smoothly," Laura Coale, director of media relations at DIA, said Wednesday. There were no reported injuries, damage or calls for paramedics, she said. The tornado was preliminarily rated an EF1 by the National Weather Service and touched down between two runways on the airport's east side.
Even in practice scenarios that assumed backed-up traffic at DIA with larger passenger loads, the airport has a safe place for everyone. In addition to the bathrooms and stairwells, the airport can evacuate people to the underground baggage tunnels if necessary, officials have said.
On May 8, 1975 — long before DIA was even conceived — an F3 tornado touched down near 56th Avenue and Picadilly Road and tracked to the northeast. It was on the ground for four miles and was a quarter-mile wide.
Back then, the area was farmland, and the twister did no damage. But if that historic tornado had been the one to hit Tuesday, it could have been a different story. That tornado's track went directly across present-day Pena Boulevard, across a runway and into the west-side parking lot next to the main terminal.
While it's true that tornadoes are much more common in Colorado than one might realize, it's equally true that they are not likely to pack the power of those that hit farther east — such as the destructive and deadly twisters that ravaged parts of Oklahoma last month.
"They certainly do occur in Colorado," said Josh Wurman of the Center for Severe Weather Research in Boulder. "Sometimes they can be quite major — there have been famous tornadoes, like the Limon tornado and the Windsor tornado, which have caused a lot of damage. There probably have been a lot of tornadoes capable of causing F4-, F5-type damage that just have churned through open rangeland, and prior to recent decades (weren't) reported at all, even as a tornado."
An I-News examination of data since 1950 kept by the National Weather Service showed that Colorado experiences frequent if not always powerful tornadoes:
• Five of the 10 counties with the most tornadoes were along the Front Range. In addition to Weld and Adams, they included El Paso, Arapahoe and Elbert counties.
• Despite their frequency, tornadoes have killed only five people in Colorado since 1950 — two people near Holyoke in 1960, two people in Holly in 2007 and one person in Windsor in 2008.
• A total of 283 residents have been injured by 53 tornadoes since 1950. More than 40 percent of the injuries came from two tornadoes — the Windsor tornado, which injured 78, and one in Thornton in 1981, which injured 42.
• The greatest concentration of tornadoes took place in the four-year time period from 1990 to 1993, spawning 283 twisters — or about one of every seven recorded since 1950. However, record keeping in the 1950s and 1960s may have undercounted tornados. The national database shows only one tornado taking place in 1959 and only two each in 1950 and 1964.
• At least 10 tornadoes have caused $1 million or more in damage.
Rating the storms
Beginning in 1971, tornadoes in the United States were categorized on what was known as the Fujita Scale, a six-step ranking — from F0, the weakest, to F5, the strongest. The different categories accounted for potential for damage inflicted by a particular tornado.
In 2007, the Enhanced Fujita Scale was adopted, updating the rating system to include a specific range of wind speed for each category of tornadoes. The new system ranked tornadoes from EF0, the weakest, to EF5, the most powerful.
Since 1950, a tornado rated either F5 or EF5 has never been recorded in Colorado. Only one twister was rated as either F4 or EF4 — a twister in 1977 in Baca County — and 21 were categorized as either F3 or EF3.
The rest were less powerful — 111 that were F2 or EF2; 531 that were F1 or EF1; and 1,229 that were F0 or EF0, including a small but dramatic tornado that startled motorists at nearly 12,000 feet on Mount Evans Road July 28 last year.
Another 55 of the state's tornadoes were listed as "unknown."
"The good news is that the vast majority of our tornadoes are weak — EF0, EF1 — so those winds go up to maybe 130 mph or so, and those tornadoes don't cause a lot of damage," said Bob Glancy, the warning coordination meteorologist at the National Weather Service's Boulder office.
Two EF5 twisters that hit the Oklahoma City area in late May took more than 30 lives and injured nearly 500 people — one in the town of Moore, and one near the town of El Reno that took the lives of two well-respected Colorado storm chasers. At one point that twister was 2.6 miles across — the widest ever recorded.
Those tornadoes were part of large, rotating storms known as supercells — which are much more common as you move east out of Colorado. Although they can occur here, they are less likely, in part because the moisture flowing north from the Gulf of Mexico doesn't often reach Colorado.
But that doesn't mean there can't be big trouble here.
"Nothing's impossible in meteorology, and the Windsor storm is an example," Glancy said.
That tornado, which touched down about 11:30 a.m. on May 22, 2008, was rated an EF3 and it was unusual in many respects — it hit before noon, it was a mile wide, it was on the ground for 38 miles, and it traveled from the southeast to the northwest.
It also killed one person, injured 78 others and inflicted $147 million in property damage, making it the most destructive tornado in state history.
"It wasn't an EF5, but that's an example of what could happen here," Glancy said.
No need to 'live in fear'
The I-News analysis also found that other historic twisters that in decades past hit harmlessly in open land could have different consequences if they struck the same places today.
On May 20, 1961, for example, a twister hit open land just outside Castle Rock where the Douglas County Courthouse stands today, and on July 19, 1985, another touched down on land where Sky Ridge Medical Center is now located.
The 2013 tornado season in Colorado is about half over. And while there's no way to predict the future, it's inevitable that the state will experience more tornadoes.
Still, Wurman, the Boulder-based weather researcher, said he'd advise people to be aware but also not overreact. There's no reason to dig a hole in the backyard and construct a tornado shelter, he said.
"If I were going to list ways to spend your money to stay safe, I would list getting a new car with better air bags higher than building a tornado shelter, because that's more likely to save your life than a tornado shelter," he said.
And he brings the perspective of having been close to twisters many times — including last month outside El Reno, when his team turned away from the tornadoes that ultimately claimed nine lives, including those of Colorado storm chasers Tim Samaras and his son, Paul.
"We don't know exactly what they did that day," Wurman said of his fellow storm scientists. "There's always a tension between being ambitious and going in and being safer and staying away. Tim has a reputation of being a reasonable guy. We don't know what happened."
Still, he said, "A tornado is pretty unlikely to be your cause of death, whether or not you live in Colorado, or in Oklahoma and Kansas, because the number of people killed every year in tornadoes, typically, is less than 100.
"People shouldn't live in fear of tornadoes."
I-News is the public service journalism arm of Rocky Mountain PBS. For more information, go to inewsnetwork.org. Contact Kevin Vaughan at 303-446-4936 or firstname.lastname@example.org.
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