Cloud streets are long rows of cumulus lined up roughly parallel to the low-level wind — the classic form of the variety radiatus. They are produced by horizontal convective rolls: counter-rotating tubes of air in which warm air rises to form the cloud rows while cooler air sinks between them, leaving clear lanes. They need an unstable surface layer capped by a stable inversion plus a moderate wind, conditions often met when cold air streams over a warmer surface.
Worth knowing
Although the lanes look like they converge to a single point on the horizon, that is pure perspective — the rows are essentially parallel. Glider pilots exploit the continuous lift along one street to fly in a straight line for huge distances.
Note
Still unsure it's the same cloud? Our app, Cloud Point— on iOS and Android — reads a photo and returns the likely type with altitude, useful when a formation is fading faster than you can look it up.
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