Clouds of the Day - Sunday, June 18, 2023 - The Cap Cloud

The photos below show a cloud capping a developing Cumulonimbus calvus. The cap cloud is a thin smooth cloud that creates a “cap” over the top of the building cloud below. The cap is a layer of moist air being lifted by the rapidly rising air. The lift has cooled the layer to its condensation level. This cloud has moved past the Cumulus congestus stage and is showing signs of losing its upward motion. The fact that the cap cloud quickly dissipates may indicate that the lifting is weakening causing the cooling of the cloud top to slow with evaporation of the cap to take over. From the first to the second photo the cloud top is becoming more rounded with fewer protuberances, which may indicate slowing updrafts.

Notice the bird silhouetted against the cloud in the lower photo. The photos were taken less than a minute apart. The upper photo was taken first.