NEWS –  A rare roll cloud was seen over Portugal’s coast, surprising beachgoers during an extreme heatwave and strong winds.

WHAT IS A ROLL CLOUD?

• A roll cloud is a rare, low, horizontal, tube-shaped cloud, part of the arcus cloud family.
• It forms at 2,000–7,000 meters altitude and appears to “roll” around a horizontal axis.
• Often seen near mountain ranges or coastal regions—notably the Alps, Japan, Scotland, and northern Australia.
• May resemble funnel clouds but are not dangerous themselves; useful for predicting severe weather.
• Their presence can signal strong winds, storms, or tornadoes.

ARCUS CLOUD TYPES:

• Arcus clouds form along the leading edge of thunderstorms or cold fronts.
• Two types: Shelf Cloud (attached to storm) and Roll Cloud (detached).
• Both result from cold downdraft air meeting warm, moist air feeding the storm.