On the evening of June 3rd, 1999 our office observed a supercell that split west of Kadoka, SD. Splitting supercells are interesting in the fact that they can produce two supercells after the split, one rotating counterclockwise, the other rotating clockwise. Take a look at the 8:10 PM MDT 4 panel reflectivity images from the KUDX WSR-88D below.
The radar images shows two distinct areas of stronger reflectivity showing the supercells splitting into right and left parts. This shows up in the Storm Relative Velocity 4 Panel product below at 8:25 PM MDT. Not how the northernmost storm is rotating clockwise and the southernmost storm is rotating counterclockwise. The upper right hand corner image shows this best in the mid-levels. The lower right hand images shows storm top divergence.
In the image below, colors that area green are parcels of air moving toward the radar and colors that are red are parcels of air that are moving away from the radar. The purple color is what we call range-folding. The radar isn't sure which direction the air is moving in the range-folded areas.
The image below is the reflectivity cross section of the splitting supercells at 8:10 PM MDT. The northernmost storm is on the left with the southernmost storm on the right. Note how the left-splitting supercell has a nicer tilt to the storm than the right-splitting supercell.
We did issue a warning on the left-splitting supercell for large hail. Reports of large hail were not received. However, much of the storm remained over non-populated areas. Left-splitting supercells are notorious large hail producers.
Look for some actual pictures of these cells taken from our Rapid City, SD office in the near future.