Most often, [[Thermal Formation]] seems random, with no discernable pattern throughout the sky. However, under certain conditions, thermals can become organized in a line known as a **thermal street**. ### Thermal Streets Thermal streets are long bands of **horizontal convective rolling** motion, oriented parallel to the wind. They require a consistent wind direction with altitude, brisk surface winds increasing by 10-20kts, then decreasing to the top of the convective layer, and a stable layer above the convective layer. If the air is moist, cumulus **cloud streets** will form in the regions of rising air. Spacing between the streets is typically 3 times the height of the convective layer. ![[horizontal convective rolls.png]] ![[cloud streets.png]] ### Thermal Wave Under specific conditions, [[Wave Formation]] can occur in the stable layer above thermal streets. This requires a wind direction perpendicular to the streets, and wind speeds increasing (>2kts/1000ft) with altitude. ![[thermal wave.png]]