Craig Setzer's Colorado Springs/Falcon, CO Chase

Here are my observations of the COS (Colorado Springs not cosine) tornado. The tornado touched down 15 miles northeast of the city and was shown on TWC Thursday night (video thanks to Al Pietrycha).

On Thursday, June 22, storms developed over extreme northwest El Paso county around 2:50 PM local. The cell remained stationary for about 30 minutes and then split with one cell moving northeastward while the second cell moved slowly southward along the lee of the Rampart Range (a 9000 ft msl mountain range running north-south to the northwest of COS). The southern cell increased to around 55dbz and then stopped southward movement 15 miles northwest of COS. The storm weakened to ~45dbz and began moving east, still to the right of the mean wind. Soon after the eastward movement began, the storm increased to >55dbz and developed a rather large wall cloud under a pronounced striated, layed region. Just before the tornado formed, a distinct rear flanking downdraft formed on the west (upwind) side of the wall cloud and visibily eroded the wall cloud leaving the appearance of a horseshoe shaped wall cloud with the open end in the rear with respect to storm movement. As the erosion took place, two rotational couplets formed, the southern couplet showing visible anticyclonic rotation and the northern couplet (core side of the horse shoe) spinning cyclonically. Shortly after the erosion process began, a funnel formed in the cyclonic couplet. During the erosion process the area of the wall cloud shrank (updraft consolidation I guess) and the visible funnel that formed decended quickly to a point halfway between cloud base and ground (cloud base was about 5000 feet agl and the funnel was viewed from up to 45 miles away.) Within minutes of the funnels decent, debris became apparent on the ground. The tornado was on the ground for about 3 minutes and dust was pulled only about 200 feet up the tube. CLouds in the cyclonic side of the horseshoe wrapped into the funnel creating the appearance of a spiraling cloud base that rapped into the smooth funnel. With time the occlusion process completed, the wall cycled and repeated the horseshoing several times without producing any more tornadoes. Viewed from the distant southeast, the storm appeared to have an anticyclonically rotating wall cloud while the mid-level cloud features rotated cyclonically. The tornado was minimal F1 and will probably be rated F0 due to barn and house damage.

One other thing, dew points in COS were in the mid 40s and increased to 50 at the time of the tornado. Shear was present but sounding speeds were light.

It's no Pampa, but we take what we can get at 6000 feet above sea level on a 50 degree dew point.

Comments welcome,

Craig Setzer