Supercells - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 176

Figure 4.8. An early simulation of a supercell using the Klemp-Wilhelmson numerical cloud
model. Horizontal cross sections of storm-relative winds (vectors) at four levels in the model at
2 h after the storm had been initiated by a thermally buoyant bubble. Updraft velocities (solid
lines) and downdraft velocities (dashed lines) are contoured at 5m s 1 increments. Shaded
regions mark regions of downdrafts in excess of 1m s 1 . The heavy solid line outlines the
rainwater field enclosed by the 0.5 g kg 1 contour. Wind vectors are scaled such that one grid
interval represents 20m s 1 . The horizontal grid spacing in the model is 1 km (from Klemp et
al., 1981).

at lower altitude. The BWER sometimes assumes an arc shape ( Figure 4.11 ), indi-
cative of a curved region of updraft (U shaped, horseshoe shaped, or crescent
shaped). The high intensity ( 50m s 1 ) of updrafts in supercells has been con-
firmed ( Figures 3.14 and 3.15 ) from measurements made by a storm-penetrating,
armored aircraft, from the ascent rate of balloons launched into updrafts, and
corroborated with measurements in numerically simulated storms by cloud

models.