Unraveling the Mystery: What is a Mackerel Sky?

Have you ever looked up at the sky and noticed a peculiar pattern of rippling, scaly clouds? If so, you’ve likely witnessed a phenomenon known as a “mackerel sky.” But what exactly does this term mean, and what kind of clouds does it describe? Let’s delve into the fascinating world of atmospheric formations and uncover the secrets behind this intriguing celestial display.

What is a Mackerel Sky?

A mackerel sky refers to a specific type of cloud formation characterized by rows of cirrocumulus or altocumulus clouds that appear to undulate in a wavelike pattern, resembling the scales of a mackerel fish. This unique cloud structure is caused by high-altitude atmospheric waves, which create a rippling effect in the cloud layers.

The term “mackerel sky” is derived from the distinct scaly appearance of these clouds, which is reminiscent of the skin pattern found on mackerel and other fish species. This visual similarity has led to the widespread use of this evocative term in meteorological circles and weather folklore.

The Cirrocumulus Cloud: The Star of the Mackerel Sky

At the heart of a mackerel sky lies the cirrocumulus cloud, a relatively rare and captivating cloud formation. These clouds are composed of small, fluffy cloudlets arranged in distinct rows or patches at high altitudes, typically between 20,000 and 40,000 feet (6,000 to 12,000 meters) above the Earth’s surface.

Cirrocumulus clouds are made up almost entirely of ice crystals, giving them a wispy, delicate appearance. They are often grouped together in a undulating pattern, resembling the scales of a fish or the honeycomb-like structure of a beehive.

The Formation of Cirrocumulus Clouds

The formation of cirrocumulus clouds is a fascinating process that involves a combination of atmospheric conditions and atmospheric instability. Here’s how it happens:

  1. Turbulent Vertical Currents: Cirrocumulus clouds form when turbulent vertical air currents encounter a pre-existing layer of cirrus clouds. These currents cause the cirrus clouds to pucker and form the distinctive puffy, cumulus-like shapes that characterize cirrocumulus clouds.

  2. Supercooled Water Droplets: The cloudlets that make up cirrocumulus clouds are often composed of both ice crystals and supercooled water droplets. Supercooled water remains in a liquid state even at temperatures well below freezing, contributing to the unique structure of these clouds.

  3. Contrails and Cirrocumulus: In some cases, cirrocumulus clouds can also form from the condensation trails (contrails) left by aircraft flying through a dry upper troposphere. These streaks can spread out and evolve into cirrus, cirrostratus, and eventually, cirrocumulus clouds.

The Weather Associated with a Mackerel Sky

While a mackerel sky is undoubtedly a captivating sight, it can also serve as a valuable indicator of changing weather conditions. Here’s what you need to know:

  • Fair Weather Precursor: Cirrocumulus clouds themselves rarely produce precipitation that reaches the ground. However, their appearance often precedes the arrival of a warm front or low-pressure system, which can bring rain or storms within 6 to 12 hours.

  • Thickening and Lowering: If you observe the cirrocumulus clouds progressively thickening and lowering into altostratus or altocumulus clouds, it’s a good sign that the warm front or low-pressure system is approaching, and precipitation may arrive within the next six hours.

  • Weather Lore: Many weather-related proverbs and sayings have been passed down through generations, emphasizing the connection between a mackerel sky and changeable weather conditions. For example, the old rhyme “Mackerel sky, mackerel sky. Never long wet and never long dry” refers to the transient nature of the weather associated with these cloud formations.

Appreciating the Beauty of a Mackerel Sky

While the mackerel sky may signal impending weather changes, it’s also a breathtaking natural phenomenon that deserves appreciation in its own right. The undulating patterns and intricate details of these clouds can create mesmerizing visual displays, particularly during sunrise or sunset when the light casts dramatic shadows and highlights across their rippling surfaces.

Many artists and photographers have been captivated by the beauty of a mackerel sky, immortalizing its unique textures and formations in their works. Famous painters like Peter Paul Rubens have depicted mackerel skies in their paintings, capturing the essence of these ephemeral atmospheric wonders for posterity.

Final Thoughts

Whether you’re a cloud enthusiast, a weather watcher, or simply someone who appreciates the wonders of nature, a mackerel sky is a sight to behold. Next time you catch a glimpse of these undulating, scaly clouds, take a moment to appreciate their intricate patterns and the fascinating atmospheric processes that brought them into existence. And remember, while a mackerel sky may signal changing weather conditions, it’s also a reminder of the ever-changing and captivating beauty of our skies.

The Mackerel Sky: A Fascinating Cloud Pattern


What type of cloud is a mackerel sky?

A mackerel sky is a term for clouds made up of rows of cirrocumulus or altocumulus clouds displaying an undulating, rippling pattern similar in appearance to fish scales; this is caused by high altitude atmospheric waves.

What is a mackerel fish like cloud?

Mackerel sky’ refers to a state of sky with extensive clouds that look like fish scales in a bright day. These clouds are small and white, and usually line themselves up in groups in a regular pattern. They resemble the small ripples created by a gentle breeze on water surface.

What type of clouds are usually found in the sky?

Thus, the 10 types are: Low-level clouds (cumulus, stratus, stratocumulus) that lie below 6,500 feet (1,981 m) Middle clouds (altocumulus, nimbostratus, altostratus) that form between 6,500 and 20,000 feet (1981–6,096 m) High-level clouds (cirrus, cirrocumulus, cirrostratus) that form above 20,000 feet (6,096 m)

What weather follows a mackerel sky?

“A mackerel sky denotes fair weather for that day, but rain a day or two after,” according to “Weather Lore: A Collection of Proverbs, Sayings and Rules,” published in 1898. By the way, the cloudlets featured in the photograph are altocumulus.

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