Cloud Atlas
Altocumulus (Ac)
Mid-level patches/rolls — the classic ‘mackerel sky’ when patterned.
How to spot it
- Rounded patches or rolls; often in groups
- Elements commonly ~1–5° (bigger than cirrocumulus)
- Sometimes shows a corona near the sun when thin
What it can mean
- Can indicate instability aloft
- May precede convection later in warm seasons
- Excellent ‘texture cloud’ for sunsets
Photography tips
- Use a longer lens to compress patterns
- Look for leading lines toward the sun
- Bracket if the sun is in-frame