Horizontal tube-shaped arcus cloud can extend hundreds of miles, last for hours
Watch rare ‘tsunami’ roll cloud hover over beachgoers in popular destination spot
Roll clouds are seen in Portugal following a heatwave as temperatures hit over 107 °F with heavy rain, thunderstorms and hail.
A rare weather sighting occurred in Portugal as tourists and locals witnessed a one-of-a-kind cloud in the sky in recent days. (See the video at the top of this article.)
A "tsunami" roll, also known as a roll cloud, filled the sky on Sunday following a heat wave, according to Euro News.
Portugal's temperatures hit over 107 °F with heavy rain, thunderstorms and hail.
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The roll sits low in the sky in a horizontal tube-shaped arcus cloud and is "relatively rare," according to the National Weather Service (NWS).
"Roll clouds usually appear to be ‘rolling’ about a horizontal axis, but should not be confused with funnel clouds," said NWS.
A rare "tsunami" roll cloud is shown filling Portugal's sky following a heat wave, with temperatures over 107°F. (ARTHUR CARVALHO/AFP via Getty Images)
Stephen Corfidi, a meteorologist at the National Oceanic and Atmospheric Administration (NOAA), previously told National Geographic the clouds are typically associated with thunderstorms.
Roll clouds "can last for several hours and extend for several hundred miles," Corfidi told the outlet.
"The 'shear' across the inversion sets up a rolling motion much like that of a rolling pin used in a bakery," said Corfidi.
Beachgoers took to social media to share videos and discuss the phenomenon.
Beachgoers have been comparing roll clouds to a tsunami from a movie. (ARTHUR CARVALHO/AFP via Getty Images)
"It was nuts to have experienced this rolling cloud in the north of Portugal. Felt like a tsunami out of a movie," said one X user.
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Another user wrote, "This cloud rolled in like an actual tsunami over Portugal."
Roll clouds sit low in the sky in a horizontal tube-shaped arcus cloud and are "relatively rare." (ARTHUR CARVALHO/AFP via Getty Images)
"Looks scary, but cool," posted an X user.
A user added, "This does look fricking cool, tbh."
