Splitting storm

A splitting storm is a phenomenon when a convective thunderstorm will separate into two supercells, with one propagating towards the left (the left mover) and the other to the right (the right mover) of the mean wind shear direction across a deep layer of the troposphere. In most cases, this mean wind shear direction is roughly coincident with the direction of the mean wind. Each resulting cell bears an updraft that rotates opposite of the updraft in the other cell, with the left mover exhibiting a clockwise-rotating updraft and the right mover exhibiting a counterclockwise-rotating updraft. Storm splitting, if it occurs, tends to occur within an hour of the storm's formation.

Storm splitting in the presence of large amounts of ambient crosswise vorticity, as characterized by a straight hodograph, produces similarly strong left and right movers. Storm splits also occur in environments where streamwise vorticity is present, as characterized by a more curved hodograph. However in this situation one updraft is highly favored over the other, with the weaker split quickly dissipating; in this case, the lesser favored split may be so weak that the process is not noticeable on radar imagery. In the Northern Hemisphere, where hodograph curvature tends to be clockwise, right-moving cells tend to be stronger and more persistent; the opposite is true in the Southern Hemisphere where hodograph curvature tends to be counterclockwise.