This is a long range view of a severe (and eventually tornadic) supercell thunderstorm fairly early in its life. You can clearly see the updraft and very impressively the overshooting top. Overshooting tops can give you a clear indication as to the strength and stability of a updraft. This overshooting top was semi-pernament. It looked exactly like you see above for quite some time, although the updraft and rest of storm did slowly evolve into a much larger storm. Overshooting tops are called such because the updraft overshoots the rest of the anvil. The top of the rest of the anvil is located by the black line. The reason the updraft overshoots is because the warm moist air inside the storms updraft is rising so fast that even when it reaches a layer of air (usually the upper troposphere or tropopause) that is stable or warmer than the updraft air it keeps rising from the momentum and push from the rising air parcels below.