What were those strange, ‘street’ clouds were spotted over Lexington?
National Weather Service forecasters say Lexington could see its warmest day of the week Tuesday, when the high will reach almost 60 degrees Fahrenheit.
Additionally, the warm air is creating some striking cloud formations, as one observer pointed out in a post on the r/lexington subreddit Sunday evening. In a shared photo, large, tube-shaped clouds in the pattern of a plowed field could be seen drifting through the sky above Fayette County.
According to NWS meteorologist Mark Jarvis, they most resemble what weather scientists call horizontal convective rolls, which Jarvis described as “streets” of clouds. The formation occurs when the right atmospheric conditions align.
What are ‘cloud streets?’
Horizontal convective rolls, or “cloud streets” as they’re commonly called, mark rising and falling masses of warming and cooling air, according to the National Oceanic and Atmospheric Administration. The air moves in a rotating or undulating motion.
Warm air rises on one side, the air cools and water vapor condenses into a cloud before sinking back down on the other side. The rolls often line up next to each other and create lines or “streets” of clouds.
As explained by Jarvis, these formations occur when an unstable layer of air lingers near the ground, while a stable layer of air is aloft. That was the case Sunday night with a return flow pattern, which typically brings warmer air into our region, the meteorologist said.
“What ends up happening is that you get turbulent rolls of wind,” Jarvis told the Herald-Leader. “Where these turbulent rolls line up, you will get ‘streets’ of clouds.”
Jarvis shared a diagram to illustrate the phenomenon, showing that where upward motion occurs, street-like formations of clouds form.
“Normally, we see them during the day and in the spring. However, if you have the right atmospheric conditions, you can really get them anytime,” Jarvis said.
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