Mesoscale convective systems - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 290

C Du

(a)

(b) C Du

C > Du

(c)

Figure 5.20. Idealized depiction of the three stages in the evolution of an MCS. (a)
Downshear-leaning updraft. (b) Upright updraft. (c) Upshear-leaning updraft, development
of stratiform precipitation region, and development of rear-inflow current (vector). Vertical
profile of low-level system-relative wind shown at the lower right. Sense of horizontal vorticity
indicated by curved arrows, with a positive sign indicating a horizontal vorticity vector into the
page and a negative sign indicating a horizontal vorticity vector out from the page. Precipita-
tion is indicated by hatched lines; cold pool is indicated by shaded area near the ground.
Scalloped line indicates the cloud edge. ''C'' qualitatively indicates the intensity of the cold pool
and D u indicates the strength of low-level vertical shear (from Weisman, 1992).