FAA Aircraft Dispatcher (ADX)MeteorologyHard
A METAR remarks section describes an observed cloud layer as nimbostratus with continuous moderate rain, though the reported base has lowered to near 800 feet AGL due to precipitation. Despite this low observed base, into which cloud family is nimbostratus classified according to standard cloud classification?
- AMiddle clouds
- BClouds of vertical development
- CHigh clouds
- DLow clouds
Show answer & explanationAnswer & explanation
Correct answer: A. Middle clouds
Nimbostratus is classified as a middle-family cloud genus, typically forming between roughly 6,500 and 20,000 feet, even though its base commonly lowers into the low-cloud altitude range due to falling precipitation. Classification is based on the cloud's typical formation level and vertical extent rather than the momentarily observed base height.
Why the other options are wrong
- B. Vertical development clouds (cumulus/cumulonimbus) are a distinct family from nimbostratus.
- C. High clouds are composed of ice crystals like cirrus, not nimbostratus.
- D. Although its base often appears low, nimbostratus is classified in the middle family by convention.
Cloud Family Classification
Clouds are grouped into low, middle, high, and vertical development families based on typical base height and structure; nimbostratus is classified as a middle cloud despite often having a low observed base due to precipitation.
- Low clouds: cumulus, stratus, stratocumulus (surface-6,500 ft)
- Middle clouds: altocumulus, altostratus, nimbostratus (6,500-20,000 ft)
- High clouds: cirrus, cirrostratus, cirrocumulus (above 20,000 ft)
- Vertical development: cumulus congestus, cumulonimbus (span multiple levels)
Memory trick: Nimbostratus 'rains low but lives in the middle house.'