Supercells - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 222

Figure 4.37. Numerical simulation of an isolated, splitting supercell for unidirectional (top
sequence) and hybrid curved low, unidirectional aloft (bottom sequence) shear profiles. Low-
level rainwater field shown at 40min intervals (related to radar reflectivity factor) at low levels
and contoured at 2 g kg 1 intervals; mid-level updrafts indicated by shaded regions; cold pool
boundaries denoted by cold front symbols. Hodographs (locations of heads of vectors indi-
cated at km AGL) of environmental winds at upper left: dashed line connecting to straight line
indicates unidirectional shear profile; continuously solid line indicates hodograph with clock-
wise-turning low-level curvature. Dashed ''L'' and ''R'' vectors indicate storm motion for
unidirectional shear and solid ''R'' vector indicates storm motion for right mover in hybrid
shear simulation. In both simulations, splitting is occurring at 80min, but the LM persists at
and beyond 120min only in the unidirectional simulation (from Klemp, 1987).
linear effects of shear interacting with an updraft (that increases with height) are
to trigger convection on the downshear side and suppress it on the upshear side
( Figure 4.39 ). How the updraft propagates, without consideration of gust front
propagation, shading/cooling underneath the anvil downstream (with respect to
the flow near the equilibrium level), and other effects, depends on the sum of non-