Mesoscale convective systems - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 296

Figure 5.23b. Bow echoes as depicted by WSR-88D radars. Radar reflectivity color-coded in
dBZ. Asymmetric bow echoes with varyingly strong mesoscale convective vortices in the
stratiform precipitation regions on (top, left) May 21, 2004 over Ohio and Michigan, on
(top, right) May 19, 2010 over southern Kansas and northern Oklahoma, and on (bottom)
August 4, 2010 over northeastern Colorado.
the front-to-rear relative flow. According to RKW theory, when low-level vertical
shear is relatively weak, the front-to-rear ascending flow is highly tilted, so that
bookend vortices are advected relatively far to the rear; when vertical shear is
stronger, the front-to-rear ascending flow is more upright, so that bookend vor-
tices are located closer to, but still behind, the leading edge of the cold pool.
Bookend vortex formation is delayed in the case of stronger low-level shear
because it takes longer for the baroclinic generation of horizontal vorticity along