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Severe Thunderstorms For The Upper Midwest; Monsoon Continues In The Southwest

Strong to severe thunderstorms will be possible today in portions of the upper Midwest into the Great Lakes region. Heavy rain, large hail, and damaging winds will all be possible, but a tornado cannot be ruled out either. The monsoonal flash flood threat remains until midweek in the Desert Southwest and Southern Rockies. Hot temperatures return to the middle of the country today. Read More >

Overview

The Greenhorn Mountain tornado is a classic example of when complex interactions between weather and steep topography create unusual outcomes.  An old wive's tale states that tornadoes cannot form across mountains, but of course, that is untrue.

Greenhorn Mountain is the tallest mountain in the Wet Mountain Range, and has two peaks.  The south peak is the highest, with an elevation of 12,352 feet.  The north peak is around 12,220 feet, near the occurrence of the brief tornado. On May 8th the road up to Greenhorn Mountain was under deep snow, and no one was up there to witness the tornado.  The only indication of a possible tornado was data from Pueblo's Doppler radar. NWS Pueblo issued a tornado warning at 2:20 p.m. MDT, shortly after, the radar indicated a strong velocity couplet (seen under the Radar tab).  The velocity couplet indicated a rotational velocity of 95 mph.  As the supercell propagated towards the north-northwest, it entered into a less favorable atmosphere to sustain it's intensity, and quickly dissipated.

In late June, NWS Pueblo received a call from a US Forest Service employee, stating that once Forest Road 369 was clear of snow, he traveled up it, and near the end of the road, encountered a damage path near, and across the road.  He remembered the tornado warning we issued on May 8th. The Warning Coordination Meteorologist (WCM) at NWS Pueblo took a trip up the road and observed the tree damage, determining that the short tornado path mirrored the location of the compact radar velocity couplet, and therefore,verified our tornado warning.  The damage path was at an elevation of 11,300 feet and the tree damage was consistent with EF1 damage (winds around 100 mph).  

 

 

 

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Greenhorn Mountain Tornado Path - May 8th

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