Cloud Streets


Cloud streets are long rows of cumulus cloud oriented parallel to the direction of wind. Cloud streets are a product of convection – rolling waves of rising warm air met by sinking layers of upper atmosphere cold air. Atmospheric science 101 – clouds form when water droplets contained in rising warm air condense on introduction to sinking cold air.

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Morning cloud streets over Vancouver Island. Image via CTV News Vancouver Island.

Thin parallel lines of clouds extending from ice shelf in black-and-white orbital photo.

The MODIS instrument on NASA’s Terra satellite captured these cloud streets over the Bering Sea on January 20, 2006. Image via Jesse Allen/ NASARead more about this image.

Cloud streets are technically called horizontal convection rolls. Typically observed from satellite eyes above, cloud streets generally form over vast expanses of ocean water. Unique to cloud streets are cloud free zones on either side created by sinking cold air.

Every cloud has a story, explanation and reason for being there. Next time you look up, remind yourself of exquisitely balanced natural forces responsible for life as we know it.