Thunderhead

A view of Mt. Florence in the late afternoon. The mountain lies east of camp; the cloud broiling up behind it is somewhere over the Great Basin. The technical term for thunderheads is cumulonimbus. They form when hot, moist air from the baking ground rises to meet cold, dry air above. When the two types of air meet, the difference in temperature causes phase changes in the water molecules in the air, resulting in the formation of a towering cloud. The process of heat rising through cold air with the help of moisture is known as an updraft, and can often happen so quickly that it sparks intense downpours and lightning to spill out of the cloud.