A Twisted Tornado Season in Colorado
The 2012 tornado season has brought two rare tornado formations to our state.
On June 8, 2012, a rare anti-cyclonic (backward-spinning) tornado touched down in Elbert County, Colorado. The tornado was classified an EF2 (on a scale of EF0 through EF5) and left a path of destruction 24 miles long by 20 miles wide. Seven homes were damaged and one was destroyed. Anti-cyclonic tornadoes are a rare event because they spin in the same direction as the storms that spawn them, meaning that the originating storm system must also be spinning opposite the normal direction. Meteorologists estimate that such events occur only 5% of the time.
On July 28, 2012, an even rarer tornado formed near Mount Evans, approximately halfway between Denver and Breckenridge, Colorado. The EF0 tornado touched down at an estimated elevation of 11,900 feet above sea level, making it the second highest tornado ever recorded. Eyewitnesses reported that the Mt. Evans tornado was weak, short-lived, and caused no damage.
High altitude tornadoes are generated by updrafts of air, pushed into the mountains by thunderstorms moving through the area, interacting with wind shear set up by the mountains, resulting in a swirling funnel made visible by water vapor. Mountainous, rough terrain typically disrupts the large-scale weather systems that give rise to most tornadoes. According to NWS meteorologist David Barjenbruch, “Areas with high elevation have less atmospheric instability, a key ingredient in tornado formation…. Instability is marked by a large temperature difference between warm, moist air near the ground and colder air higher up, which gives rise to thunderstorms and tornadoes.” (http://www.ouramazingplanet.com/3263-second-highest-tornado.html). As a result of these conditions, high-altitude tornadoes are extremely rare.
- Mount Evans tornado could be second highest recorded (denverpost.com)
- Drought’s silver lining: Record few tornadoes (msnbc.msn.com)
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