Ordinary-cell convective storms - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 151

Figure 3.44. (Top) Idealized depiction of the vertical cross section of clouds and radar echoes
in a multicell convective storm, as seen in the plane of the mean vertical shear vector or,
equivalently, from the right side of the storm with respect to its motion (in the Northern
Hemisphere). What were originally called ''feeder clouds'' are now recognized as a continuous
''flanking line''; mature cells are on the right and a new cell is seen aloft in the center. Lines of
constant radar reflectivity factor in dBZ are given by the dashed lines; low-level inflow into the
updraft is indicated by the red streamline and the cold surface outflow is indicated by the green
vector (adapted from Dennis et al., 1970). (Bottom) Multicell convective storm in eastern
Colorado on July 13, 1996. New cumulus growth is seen being forced along the edge of a
gust front denoted by the dashed line (photograph by the author).
A succession of ordinary cells, each of which is independent of each other and
initiated along the gust front from an ordinary convective cell, is referred to as a
''multicell'' convective storm ( Figure 3.45 ). In some numerical simulations (see
papers by Rob Fovell and coauthors), new cells grow approximately once every
15min. The periodic nature of new-cell growth is linked to the temporary suppres-
sion of new-cell growth by sinking motion on the flanks of the existing updraft;
these sinking regions are associated with the horizontal circulations induced by
the gradient of buoyancy at the edges of the buoyant updraft ( Figure 3.46 ). Also,