Late Day Tornado Near Otis, Colorado

All images and text © copyright Gene Moore
unless otherwise indicated

On this day I was chasing an area in eastern Colorado. My early morning forecast had anticipated storms too far south. I had to recover to development much further to the north. Clear skies allowed good visibility to the targeted cell. I was able to pick the correct road that would bring me into the mesocycone from the south. Since I was running late the trip north was filled with considerable anxiety concerning what I was missing. As it turned out I did miss an earlier tornado, but managed to intercept the mesocyclone for the last major event of the day. I featured the storm because the structure was exceptional. A prime example of a high plains supercell.

  Isolated supercell with mesocyclone

Isolated supercell in northeast Colorado. Note the inflow into the cylinder shaped tower on the southwest side of the storm; a classic supercell. Banding may bee seen spiraling up the side of the rotating cloud. The mesocyclone is well defined as a rotating updraft; although it's associated with a large storm. The high convective condensation level on this day allowed me to see under the storm from a great distance. At least I was not missing a tornado at the time of this image.

a surge of wind from the core rotating dust and a vortex spins up

About 30 minutes after arriving at the storm the mesocyclone began to extend a circulation to the ground. In this image, outflow from the core area of the storm is lifted into the updraft under mesocyclone.

Dust and dirt is lofted about 1000 feet into the air under the developing wall cloud. Separate vortices are beginning to form while rotating cyclonically around the base of the lowering.

a lowering wall cloud -strong rotation two intense circulations

A well defined lowering appeared under the rotating storm base. The rotation concentrated in this area spinning up dirt circulations on the ground.

The two circulations pictured here were strong enough to be considered weak tornadoes. The rotation at cloud base was reaching tornadic speed. This show would persist until after sunset.

  tornado decends - incr brightness

Dirt is flung violently as the tornado begins to take shape. The forming funnel is the bulbous lowering in the center of the image. A mass of rotating dirt was all that could be seen under the mesocyclone soon after this shot was taken. So many times chasers witness a forming tornado in the waning minutes of daylight. I moved north to better backlight the next shot, but the "photography" light was gone. I could see the tornado quite well in the fading twilight. A block of rotating dust persisted into the darkness. I lost sight of it as the storm moved east.

  storm east after sunset

A 15 second shot of the departing storm after the sun set. The cell is weaker, but retains a well defined inflow. No additional tornadoes were reported. The bright white area in the top of the storm was enhanced by intra-cloud lightning.

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