A splitting storm is a storm that splits into 2 storms with diverging paths. One storm is called a left mover and one is called a right mover. The left mover will most likely weaken and dissipate, but could potentially, on rare occasions, evolve into a very severe and anticyclonically (clockwise) rotating supercell

Supercell

A supercell is a thunderstorm that is characterized by the presence of a mesocyclone: a deep, continuously-rotating updraft. For this reason, these storms are sometimes referred to as rotating thunderstorms...

 thunderstorm

Thunderstorm

A thunderstorm, also known as an electrical storm, a lightning storm, thundershower or simply a storm is a form of weather characterized by the presence of lightning and its acoustic effect on the Earth's atmosphere known as thunder. The meteorologically assigned cloud type associated with the...

. The right moving storm has the highest potential of becoming a severe thunderstorm or a supercell.