Thursday, June 13, 2013 9:19:01 AM
At 0:43, this is a textbook vault(area of no rain) of a leftmover supercell probably cause by a cold front.
The lower base is a wall cloud and is caused by a moist downdraft colliding with the storms rotating updraft. The air is pushed down under a heavy water laden downdraft then caught by a violent rotating updraft, causing a area of lowered clouds.
The rain cloud on the right is the back of a shelf cloud, it is a moist cold downdraft that cuts under warm air and produces rain.
Notice at 43 also the small amount of rain in the back of the wall cloud, it is the rear flank down draft. It is warm dry air that is taken from mid way up the storm wrapped around the updraft once and then forced down carrying some warm raindrops it caught with it. You may notice it increase with the up draft because it is thought to create a positive feedback, this is what usually creates tornadoes.