Clouds of the Day - Thursday, December 23, 2021

Summer Sky vs Winter Sky

Summer skies are dynamic - with exciting action. Winter skies are more placid. But don’t be fooled. Compare the photos below. The first one was taken in June of 2021. The second was taken today, December 23, 2021.

In June the sky was roiling with turbulence. Warm moist air was rising rapidly producing bulging clouds called cumulus congestus (large, congested cumulus) and cumulonimbus (thunderstorm). Today the clouds looked serene with a layer of altostratus (high stratus) and another layer of weak (almost flat) cumulus. Upward motions in cumulonimbus sometimes exceed 60 mph while altostratus form where air is rising a few inches per second. Thunderstorms are intense localized storms while altostratus or altocumulus form in vast cloud sheets covering many 10s or 100s of square miles.

The clouds shown below show the contrast between summer and winter skies.

Cumulus congestus and cumulonimbus in background.

Altostratus in background and altocumulus in the foreground. The Sun is visible through the clouds.