Definition
A synoptic-scale cloud pattern, visible in satellite imagery, that takes the shape of a comma and marks the position and circulation of a developing or mature mid-latitude low-pressure system. The head of the comma sits over the low's center and the tail trails southward along the trailing cold front.
Plain English
A large, comma-shaped cloud pattern seen from satellites that shows where a storm system is and which way it's spinning.
Context Anchor
Seen in aviation weather discussions, satellite images, and briefings about large-scale weather systems.
Derivation
Named simply for its shape — the cloud mass on a satellite image looks like a written comma, with a rounded head and a curving tail. The visual resemblance is the whole reason for the name.
Why Pilots Care
Recognizing this pattern helps anticipate the location of turbulence, icing, and strong winds associated with the storm.
Analogy
It is like seeing a swirl pattern in cream stirred into coffee: the shape helps you see that the air is organized and moving, not just scattered randomly.
Intuition Check
Do not think of a comma cloud as a single cloud shaped like punctuation outside the windshield. It is a large cloud pattern seen best from above on satellite imagery.
Example Sentence 1
The forecaster pointed to the comma cloud over the Midwest and noted the low was deepening rapidly.
Example Sentence 2
Comma clouds often appear ahead of a cold front, prompting the crew to plan a route that avoids the worst weather.