By Ashton Altieri

BRIGGSDALE, Colo. (CBS4) – A thunderstorm in rural northeastern Weld County strengthened enough to produce an unusual tornado Wednesday morning. A generous amount of low level circulation in the storm spawned a brief tornado touchdown in an open field about 13 miles east of Briggsdale. This area is about 70 miles northeast of Denver not far from the the Pawnee National Grassland..

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At 6:37 a.m. a trained weather spotter in Weld County spotted the tornado on ground. There have been no reports of damage or injuries.

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Late night and early morning thunderstorms are somewhat common from late July through early September on the Eastern Plains of Colorado. And occasionally these storms can become severe due to damaging wind or large hail. What is rare is for these storms to become tornadic because daytime heating is usually a necessary ingredient for tornado development in Colorado.

Early Wednesday morning there was just enough change in wind direction with height (a concept known as wind shear) to produce the rotation needed for a tornadic storm. The Boulder office of the National Weather Service estimates a tornado forms on the Eastern Plains between 12 a.m. and 7 a.m. only once every 8-12 years.

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Ashton Altieri is a Certified Broadcast Meteorologist. Watch him on the CBS4 Morning News weekdays from 4:30 a.m. to 7 a.m. Connect with Ashton on Facebook and on Twitter @AshtonCBS4.