Cloud Nomenclature (Met) Flashcards
What does the prefix “Virgo” mean?
That precipitation falls from this cloud, but evaporates before it reaches the floor.
What are the boundaries and broad characteristics of the three cloud stories?
Low is 0-8000ft, middle is 8000-20,000ft, and high is 20,000ft upwards. Low is all water droplets, middle is a mix of water droplets and ice crystals, high is all crystals.
What are the characteristics and risks of nimbostratus clouds, and what is their reference code?
Nimbostratus is a widespread cloud spreading across multiple stories. Usually leads to long-duration mild rain. If high enough, can cause rime ice. Not very turbulent. NS.
What are the characteristics and risks of cumulonimbus clouds, and what is their reference code?
Cumuliform clouds climbing through all 3 stories. Very turbulent, containing large chunks of clear ice and supercooled droplets. Frequently leads to hail, thunderstorms and short-duration heavy rain. CB.
What are the characteristics and risks of cirrus clouds, and what is their reference code?
Cirrus clouds are thin, wispy strands of cloud in the highest story. They are so light and thin, they do not cause any turbulence, any precipitation, or any icing risk. CI.
What are the characteristics and risks of stratocumulus clouds, and what is their reference code?
Stratocumulus are stratus clouds with a cumulus cloud rising through them. They are moderately turbulent, contain a mix of rime and clear ice risks, and do not generally cause precipitation. Mainly encountered in the lower stories. SC.
What are the characteristics and risks of cumulus clouds, and what is their reference code?
Cumulus clouds generally form in the lower story, but can rise into the middle, in which case they are called towering cumulus (TCU). They pose moderate turbulence risks, can contain rime ice, if tall enough, and lead to showers of rain. CU.
What are the characteristics and risks of altocumulus clouds, and what is their reference code?
Altocumulus are cumuliforms confined to the middle story. They look like sheep. Moderate turbulence risk, and some clear ice or supercooled water formations. No precipitation. AC.
What are the characteristics and risks of cirrocumulus clouds, and what is their reference code?
Cirrocumulus are cumuliform clouds which have risen to the top story. They cause a rapid, juddery turbulence, but no ice or precipitation risks. CC.
What are the characteristics and risks of stratus clouds, and what is their reference code?
Stratus clouds are low level, very thin and wide clouds. They cause long-duration drizzle over a wide area, but pose no turbulence risk, and very little icing risk unless it is very cold. ST.
What are the characteristics and risks of altostratus clouds, and what is their reference code?
Altostratus are middle-layer stratiform clouds. Like most stratiform clouds, no turbulence risk, and also no precipitation, however rime ice is a possibility. AS.
What are the characteristics and risks of cirrostratus clouds, and what is their reference code?
Cirrostratus are the highest of the stratus clouds, and are sometimes left behind by the anvils of cumulonimbus clouds, or the top layers of Foehn systems. They pose no threat of icing, turbulence or precipitation, and are basically just thicker, more even cirrus clouds. CS.
What are the categories of cloud cover available from a ceilometer?
Few, which means 1-2 octares, scattered, which means 3-4 octares, broken, which means 5-7 octares, and overcast, which means 8 octares. 9 means a reading is not available or the sky is obscured.
What do CAVOK and NSC mean, and what is the difference?
CAVOK is clouds and visibility OK, and NSC is no significant clouds. In both, clouds must be above 5,000ft, or the minimum safe altitude, whichever is greater, and there must be no cumulonimbus or towering cumulus clouds. CAVOK is a stricter term: it also requires visibility to be at least 10km, and no significant weather to exist.
What do ISOL, LYR and EMBD mean?
ISOL - isolated, i.e. clouds of this type, but only in a few places.
LYR - layered, i.e. distinct bands of cloud separated vertically by empty sky.
EMBD - embedded, i.e. one sort of cloud sticking into or out of another.
