Ordinary and Out of the Ordinary Clouds

Altocumulus, Cirrus spissatas, Cirrus fibratus, with fall streaks, Copyright 2020 by Craig Johnson, Weather Briefing, LC

This photo from late August 2020 shows includes ordinary and not so ordinary clouds. Cirrus spissatus are out of the ordinary but they occur often enough to be seen several times a year. Cirrus spissatus may appear grayish on the side facing away from the Sun. They often originate when a piece of thunderstorm anvil is separated from the top of the storm. As in this photo, cirrus spissatus may appear to be a middle level cloud because of the thickness and shape.

Cirrus are high clouds made mostly or entirely of ice crystals. They are found above 16,500 feet (5,000 meters). Most cirrus are thin or wispy and allow the Sun to shine through. Cirrus spissatus appear as dense clumps and often have ice crystals trailing the parent cloud (fall streaks). The spissatus and fall streaks in this photo are complex with a second layer of spissatus or a mid-level cumulus cloud variety in the form of a roll along the bottom of the photo. It is hard to determine from this distance. Cirrus spissatus often hides the Sun and is the only type of cirrus that will hide it. In the photo, the dense cloud in the center and left center of the photo is cirrus spissatus.

Cirrus fibratus are the hair-like filaments streaming off the spissatus in the upper center and are the thin finger-like fibrous patches at the right center.

Altocumulus are common mid-level clouds. They are in the upper right corner of this photo and are also seen with the blue sky background between the fall streaks (virga) in the center/left center. The altocumulus clouds are lower than the fall streaks (virga) in the foreground but appear to be higher because of their greater distance from the spissatus and the fall streaks being in the foreground.