http://glidingforecast.on.net/RASP/RASPtable.html

Combining the previous two parameters, this depicts the Cumulus
Cloudbase only at locations where the Cumulus Potential parameter is positive.
This single plot can be used, instead of needing to look at both the Cumulus
Potential and Cumulus Cloudbase plots, if the threshold Cumulus Potential
empirically determined for your site approximately equals the theoretical value
of zero. For locations where the actual threshold is greater than zero, as is
often the case, this depiction will over-estimate the extent of the cumulus
region