Components of the tornado are illustrated here. The long, skinny cloud extending almost to the surface is the condensation funnel.  Surrounding this feature and extending to the ground is the debris cloud which is a clear indicator that the tornadic circulation has reached the ground.  In this case, the debris cloud is composed primarily of dirt and dust.  Notice the lack of a wall cloud at the top of the tornadic circulation.  Though wall clouds accompany most tornadoes, we see here that this is not always the case.  Directly in front of the tornado there is a small clearing in the clouds.  This may be due to the storm's rear flank downdraft, which is air rushing down from the midlevels of the storm to the surface (this sinking motion can cause drying and clearing in the clouds).  The rear flank downdraft is believed to be important to tornado formation.