Definition
Long, narrow bands of cirrus cloud that form along the edge of a jet stream, where strong high-altitude winds and sharp temperature differences cause ice crystals to develop and stretch out in the direction of the airflow.
Plain English
High, wispy clouds shaped into long streaks by the very fast winds of a jet stream. Their pattern marks the path and edge of those high-altitude winds.
Context Anchor
Seen in weather reports, weather briefings, and visual weather observation when considering winds aloft and possible turbulence near the jet stream.
Derivation
Cirrus comes from the Latin for 'curl' or 'tuft of hair,' describing the thin, wispy look of these clouds. Jet stream describes the fast, narrow river of air at high altitude. Put together, the name points to wispy clouds shaped by that fast-moving air.
Why Pilots Care
These clouds often indicate areas of possible clear air turbulence and strong winds that affect route selection, fuel burn, and ride comfort.
Analogy
They are like long streaks in water that show where a fast current is moving, except these streaks are made of ice crystals high in the sky.
Grounding Statement
Picture thin, streaky clouds high above you, all stretched in the same direction like combed hair, marking where a powerful high-altitude wind is flowing.
Intuition Check
Do not assume all cirrus clouds mark a jet stream. Jet stream cirrus specifically refers to cirrus formed in or near the fast winds of a jet stream.
Example Sentence 1
On the satellite image, a long band of jet stream cirrus stretched across the route, warning the crew to expect turbulence near that altitude.
Example Sentence 2
We adjusted our flight plan after noting jet stream cirrus forming across our intended route.