The type of cloud that is most likely to precede a tornado is a wall cloud.
Wall clouds are the best identifier of a tornado being possible.
The wall cloud which precedes a tornado is a compact, lowering of the cloud where an updraft and inflow of a storm is located.
There is also a lot of movement here and when they are rotating wall clouds the funnel clouds and the tornadoes can descend from them as well.
A wall cloud is a large, localized, persistent, and often abrupt lowering of cloud that develops beneath the surrounding base of a cumulonimbus cloud and from which tornadoes sometimes form.
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.
A wall cloud that may produce a tornado can exist for 10–20 minutes before a tornado appears, but not always.
A shelf cloud will usually be associated with a solid line of storms.
The wind will come first with rain following behind it.
It may appear to rotate on a horizontal axis.
Wall clouds will rotate on a vertical axis, sometimes strongly.
Translated from latin meaning wall, the 'murus' cloud feature is found only in the cumulonimbus cloud type.
No other cloud type besides a cumulonimbus cloud can be paired with a murus cloud feature.
Murus, more popularly known as wall clouds, are cloud lowerings forming below the updraft base of a cumulonimbus cloud.
Researchers have shown that wall clouds probably develop when some rain-cooled air is pulled upward, along with the more buoyant air, as the strengthening updraft attempts to replace ever-growing volumes of rising air.