Good Explanation of Capping

A friend of mine shared this on Facebook, thought it was worth posting here. Though mentioning Dallas, the principle is the same wherever.
Steve McCauley


Here is your CAP PRIMER to refresh (or introduce) the concept of The Cap. Basically it's a layer of warm air aloft that acts like a LID and prevents surface air bubbles from climbing very high into the atmosphere. And if you can't get these air bubbles to rise very high, you can't form towering thunderclouds.

Think of the air bubbles as individual hot air balloons. As long as the air inside the balloon is warmer than the surrounding environment, the balloon will rise. But if you try to fly the balloon into an area that is just as warm as it is, the balloon will no longer go up. It gets trapped in the cap.

Same thing happens with rising air bubbles. If ascending surface air bubbles encounter warm air aloft, they stop rising, and voila, you have prevented thunderstorm formation. But if you can get the surface air bubbles hot enough, then they may just have enough energy to punch through the cap and get to the very cold air on the other side. This leads to explosive thunderstorm development.

Of course, there is a way around this barrier. If you have some high-altitude moisture flowing ON TOP of the cap, you can indeed make storms that way. These storms do not have to "break through" anything. These are what we call "elevated" storms since they can develop on top of the cap, but that would be cheating.