Cloud Identification and Classification

Understanding cloud classification and reporting is integral to meteorology for aviation. Pilots must not only recognize different cloud types by appearance but also understand the standard abbreviations and methods used to report them in aviation.

Cloud Classification by Height

High-Level Clouds (5 - 13 km / 16,000 - 43,000 ft)

1. Cirrus (Ci)

   • Characteristics: Thin, wispy; composed of ice crystals.
   • Variants: Castellanus, Fibratus, Uncinus
   • Source: Cloud Types - UCAR Center for Science Education

2. Cirrostratus (Cs)

   • Characteristics: Veil-like; can cause halo phenomena around the sun/moon.
   • Variants: None
   • Source: Cloud Classifications and Characteristics - National Weather Service

3. Cirrocumulus (Cc)

   • Characteristics: Small, white patches resembling grains.
   • Variants: Castellanus, Stratiformis
   • Source: Cloud Classifications and Characteristics - National Weather Service

Middle-Level Clouds (2 - 7 km / 7,000 - 23,000 ft)

1. Altocumulus (Ac)

   • Characteristics: White or gray patches often appearing in layers or patches.
   • Variants: Castellanus, Lenticularis
   • Source: Ten Basic Clouds - NOAA

2. Altostratus (As)

   • Characteristics: Gray or blue-gray clouds usually covering the sky, allowing sun/moon to be dimly visible.
   • Variants: None
   • Source: Ten Basic Clouds - NOAA

3. Nimbostratus (Ns)

   • Characteristics: Thick layer producing continuous precipitation.
   • Variants: None
   • Source: Cloud Classification - National Weather Service

Low-Level Clouds (Surface - 2 km / Surface - 7,000 ft)

1. Stratus (St)

   • Characteristics: Uniform, flat; often gray and can cover the entire sky.
   • Variants: Fractus
   • Source: Cloud Classification - National Weather Service

2. Stratocumulus (Sc)

   • Characteristics: Lumpy clouds covering the sky in patches, creating formations like tessellations.
   • Variants: Castellanus, Stratiformis
   • Source: Ten Basic Clouds - NOAA

3. Nimbostratus (Ns)

   • Characteristics: Produces steady, widespread precipitation.
   • Variants: None
   • Source: Cloud Types - UCAR Center for Science Education

Clouds with Vertical Growth (Surface - 13 km / Surface - 43,000 ft)

1. Cumulus (Cu)

   • Characteristics: Dense with clear outlines; develops vertically.
   • Variants: Humilis, Mediocris
   • Source: Cloud Classification - National Weather Service

2. Cumulonimbus (Cb)

   • Characteristics: Towering and associated with severe weather.
   • Variants: Mammatus
   • Source: Cloud Classification - National Weather Service

Cloud Type Abbreviations

• Ci: Cirrus
• Cs: Cirrostratus
• Cc: Cirrocumulus
• As: Altostratus
• Ac: Altocumulus
• Ns: Nimbostratus
• St: Stratus
• Sc: Stratocumulus
• Cu: Cumulus
• Cb: Cumulonimbus

Methods to Report Cloud Amount in Aviation

METAR Reports

• SKC: Sky clear
• CLR: Clear skies (no clouds below 12,000 feet AGL)
• FEW: Few (1-2 okta)
• SCT: Scattered (3-4 okta)
• BKN: Broken (5-7 okta)
• OVC: Overcast (8 okta)

Each condition is typically followed by a three-digit number indicating the height above ground level (AGL) in hundreds of feet. For instance, SCT025 represents scattered clouds at 2,500 feet AGL.

TAF (Terminal Aerodrome Forecast) Reports

• Use of codes like NSC, FEW, SCT, BKN, and OVC to represent cloud cover.
• Additional significant weather phenomena impacting cloud reporting for visibility and flight safety.

Note: Vertical Visibility (VV) is used when obscuration prevents cloud ceiling from being measured, indicating an indefinite ceiling with a height.

In learning about cloud classification and reporting, aspiring pilots can better interpret meteorological phenomena crucial to flight safety and navigation.