September 03, 2004
This photo showing a classic multi-cell thunderstorm in a low wind shear environment was captured on July 9, 2004 above Memphis, Tennessee. A multi-cell thunderstorm consists of a group of cells, moving along as one unit, with each cell in a different phase of the thunderstorm life cycle. New cells tend to form on the upwind (usually western or southwestern) edge of the cluster. A new cell can be seen developing on the lower left (western) flank of the mature thunderstorm in the center. Dissipating thunderstorms are visible to the right of the mature central storm.
Based on this storm's appearance, tall and vertical with no real "tilt" to the tower, vertical wind shear was not significant, thus favoring the formation of this multi-cell thunderstorm with short-lived updrafts. Wind shear is the variation in wind speed (speed shear) and/or direction (directional shear) over a short distance. This term usually refers to vertical wind shear -- the change in wind with height.