Shelf Clouds 

Shelf Clouds (Arcus Clouds)

• It is a low-hanging cloud that appears to be attached to the front of a storm.
• It is often dark and ominous, and it can give the impression that the storm is moving in quickly.
• These clouds are sometimes seen beneath cumulonimbus clouds, the dense, towering vertical cloud that causes intense rain.

Formation of Shelf Clouds

• These are formed when a thunderstorm pushes a gust of wind ahead of it.
• This gust of wind can be so strong that it lifts the warm, moist air in front of it.
• As the warm air rises, it cools and condenses into a cloud, which becomes the shelf cloud.
• The shelf cloud is often accompanied by a strong gust of wind, which can be dangerous to those caught in its path.
• This rush of cold air often occurs in a thunderstorm’s downdraught, where cold air rushes towards the ground before spreading out to create a gust front.
  • A thunderstorm is a rain shower during which you hear thunder. Since thunder comes from lightning, all thunderstorms have lightning.

Distinctive Features

• These have a distinct horizontal appearance (Roll Cloud), stretching across the sky in a straight line.
• They often take on a wedge-like or arc-shaped structure, curving upward toward the storm’s main cloud base.
• These have a well-defined, solid line separating the cloud formation from the sky.

Impact / Indication of Shelf Cloud

• It is often a sign of severe weather, which can cause damage to structures, power lines, and other infrastructure.
• The storm that follows the shelf cloud can also produce heavy rain, hail, and even tornadoes, which can cause flooding, landslides, and other hazards.

Frequency

• In India, Arcus clouds formation is rare phenomenon.
• However, they are seen around the world routinely in places such as Australia, Alaska, California, etc., during powerful thunderstorms.