The white region is called the "positive energy" region. The area of this region is CAPE and is expressed in Joules/kg values. The larger this area, the more CAPE, and the more energy that is available to rising parcels. A CAPE value that is more concentrated in the lower half would produce a stronger updraft than an equal CAPE value that is stretched higher and narrower. Also, CAPE is directly related to the maximum potential vertical speed within an updraft. Faster updrafts means more powerful updrafts. Powerful updrafts aid in the creation of large hail, supercells and violent tornadoes.
The chart below can be used to gain a greater understanding of what numerical values of CAPE indicate as it relates to convection of air parcels. Remember, CAPE is only the potential energy. High CAPE values cannot be used as a predictor about whether or not severe weather is going to take place at a given time or that severe weather is looming.
CAPE value Convective potential
0 Stable
0-1000 Marginally Unstable
1000-2500 Moderately Unstable
2500-3500 Very Unstable
3500 + Extremely Unstable