Tornadoes rare, usually weak, but not unknown in mountainous areas
Wyoming twister in 1987 was uncommonly large
by Allen Best
LAKE GEORGE, Colo. – In early June, a small but unusual tornado spun across Colorado’s South Park, damaging several homes, uprooting trees, and knocking over power lines near the community of Lake George. See video.
A tornado of that magnitude would barely make the news in Oklahoma or Alabama, in what is called North America’s tornado alley. In Colorado, it was news precisely because of its rarity.
Why aren’t tornadoes more common in the mountains? Writing on a website called US Tornadoes, meteorologist Kathryn Prociv explains that higher elevations typically have cooler, more stable air. Energy of warm and humid “unstable” air is required to create the explosive thunderstorms in which tornadoes originate.
Those conditions do exist occasionally. The highest ever recorded in the United States was at 12,000 feet in Sequoia National Forest in California. That was in 2004. The second highest was at an elevation of 11,900 feet on Mount Evans, southwest of Denver in 2012. See video and still images.
The most destructive tornado at a higher elevation shredded a 24-mile path through Yellowstone National Park and the Teton Wilderness Area in 1987. In some places, the swath was a mile and a half. Winds speeds were estimated at between 207 and 260 mph, and an estimated million trees were uprooted.
This was in mid-summer, and you’d think somebody would have been camped out there. But no injuries were reported. Most of the damaged forest burned the next year in the Yellowstone fires. For a scientific description, see paper by Theodore Fujita (father of the F-scale for measuring tornadoes). Also see Wikipedia entry.
That Yellowstone tornado was assigned a rating of EF4 on the Fujita scale, just one step below the very worst, such as the one that killed 24 people near Oklahoma City last year.
In Colorado, as you can see from the above map, tornadoes are rare in the mountains and on the Western Slope. Little or no damage has been caused to human resources.
The strongest tornado on the Western Slope since record-keeping began in 1950 occurred in Pitkin County. That was on June 20, 1975. The intensity was rated F-2 on the rating system then used, which begins at F-0 and goes to F-5, such as is assigned the tornadoes in the Midwest. Winds of at least 110 mph were attained.
There were likely more tornadoes that weren’t reported, says Jim Pringle, a meteorologist with the National Weather Service in Grand Junction.
Consider Stoner, located between Rico and Dolores, in southwestern Colorado, a hamlet that once had a small ski area and it still has an RV park. Dropping by, Pringle was told by the proprietor that a tornado had occurred three years prior. Uprooted trees were the evidence. However, because the report was made 18 months after the event, it was not eligible to be entered into the record books.
Another time, somebody sent him a photo of a funnel-shape descending from a cloud in the Grand Valley west of Rifle. Because it did not reach the ground, however, it is not considered a tornado.
“For every tornado reported, probably a dozen funnel clouds occur. We get a lot of funnel clouds, but they don’t actually reach the ground,” says Pringle.
Another significant tornado occurred on Oct. 10, 1997, between Creede and the Wolf Creek Ski Area. That was at about 10,000 feet in elevation, near Fisher and Copper mountains, and it ripped an estimated four million board feet of wood out of the ground. Several hunters saw it. It ranked as an F-2.
If you know where Creede and Wolf Creek are, you can pick out the site as the large yellow circle in this map: http://www.denverpost.com/news/ci_25814431/interactive-graphic-history-tornadoes-colorado
Tom Magnuson, warning coordination meteorologist at the National Weather Service office in Pueblo, Colo., notes that it was a turbulent month in Colorado. A few days later in 1997, a frenzy of tornadoes hit Southeast Colorado. On Oct. 25, winds in excess of 100 mph blew over the Continental Divide north of Steamboat Springs and downed trees on 20,000 acres. Soon after, a giant snowstorm blanketed the Great Plains.
Dead tree kills hiker in Yellowstone Park
WEST YELLOWSTONE, Mont. – A 36-year-old man from Taiwan was in the wrong place at the wrong time in Yellowstone National Park.
The Jackson Hole News&Guide explains that he left a trail and was ascending a slope in an effort to get a better view of Grand Prismatic Spring, a colorful hot spring north of Old Faithful, when a lodgepole pine fell and hit him in the head. He was killed.
The pine itself had died in the great fire of 1988. Park Service officials said it was windy when the tree fell.