A towering cumulus cloud--precursor of a cumulonimbus, or thunderstorm, cloud--builds skyward. These cauliflower-like clouds result from warm, moist air rising rapidly through a cooler layer. These clouds usually have a horizontal base and a dome-shaped upper surface that frequently resembles a head of cauliflower and show strong contrasts of light and shadow when the sun illuminates them from the side.
Courtesy of UCAR Digital Image Library