What does a wall cloud do?

Question

What does a wall cloud do?

Answer 1

A wall cloud is an isolated cloud lowering attached to the rain-free base of the thunderstorm. The wall cloud is usually to the rear of the visible precipitation area. Wall clouds are about two miles in diameter and mark the area of strongest updraft in the storm.

As the storm intensifies, the updraft draws in low-level air from several miles around. Some low-level air is pulled into the updraft from the rain area. This rain-cooled air is very humid; the moisture in the rain-cooled air quickly condenses below the rain-free base to form the wall cloud.

A wall cloud that may produce a tornado usually exists for 10-20 minutes before a tornado appears. A wall cloud may also persistently rotate (often visibly), have strong surface winds flowing into it, and may have rapid vertical motion indicated by small cloud elements quickly rising into the rain-free base.

Answer 2

It doesn't really "do" anything different than any other cloud.  A wall cloud is simply a particular type of cloud that develops when air in nearby rainfall is lifted up into the storm.  That air, being more moist than the surrounding air due to rain having fallen in it, condenses it's water vapor at a lower level, thus producing a lowered base to the storm.  It does not always signify a tornadic situation, but in some cases can be a precursor to them.