Towering cumulonimbus clouds are typically accompanied by smaller cumulus clouds. Cumulonimbus clouds are the final form of growing cumulus clouds. Stratocumulus Cumulogenitus out of cumulus or cumulonimbus clouds, disrupted by decreasing convection. Cumulus humilis clouds usually indicate fair weather. They are an intermediate stage between cumulus mediocris and cumulonimbus. Droplets of supercooled water often exist in stratus and cumulus clouds. The ceiling was overcast at above ground level with towering cumulus clouds. Frigatebirds are found over tropical oceans, and ride warm updrafts under cumulus clouds. Cumulus clouds form via atmospheric convection as air warmed by the surface begins to rise. Like Uranus, Neptune has methane cumulus clouds. Showers of moderate to heavy intensity can fall from cumulus congestus clouds. They form at the bases of cumulus congestus clouds over tropical and subtropical waters. Any showers from stratocumulus castellanus are not usually as heavy as those from cumulus congestus. This creates the characteristic flat-bottomed puffy shape associated with cumulus clouds. Next year, Stormfury began by conducting experiments on cumulus clouds.