mm43;
... thinking about the potential density/temperature of the contents of a rapidly rising Cb cell.
The buoyancy of rising air is due to it being lighter (less dense) than its surroundings. It is about 3 degrees C warmer than the atmosphere at FL350 (based on figure 11 of Tim Vasques' analysis), but the pressure is the same. For one cell to develop significantly higher gust velocity than its neighbors, I think it must either get its air from a hotter source on the surface, or the surrounding atmosphere must be cooler than elswhere. The higher velocity would result in more 'overshoot', which would show up as lower temperature of the cloud tops in satellite IR imagery.
regards,
HN39