Warm fronts associated with extratropical cyclones tend to generate mostly cirriform and stratiform clouds over a wide area unless the approaching warm airmass is unstable, in which case cumulus congestus or cumulonimbus clouds will usually be embedded in the main precipitating cloud layer.
12.
Cirriform clouds that form higher up in the stratosphere and mesosphere have common names for their main types, but are sub-classified " alpha-numerically " rather than with the elaborate system of Latin names given to cloud types in the troposphere.
13.
The genus types are arranged from top to bottom in the same ascending order for each �tage . ( 1 ) = Stratiform types, ( 2 ) = Cirriform types, ( 3 ) = Stratocumuliform types, ( 4 ) = Cumuliform types, ( 5 ) = Cumulonimbiform types.
14.
Under Luke Howard's first systematized study of clouds, carried out in France in 1802, three general cloud " forms " were established based on appearance and characteristics of formation : " cirriform, " " cumiliform " and " stratiform ."
15.
With highly unstable atmospheric conditions, large cumulus may continue to grow into cumulonimbus " calvus " ( essentially a very tall congestus cloud that produces thunder ), then ultimately into the species " capillatus " when supercooled water droplets at the top of the cloud turn into ice crystals giving it a cirriform appearance.
16.
In addition to these three main types, Howard added two names to designate multiple cloud types joined together : " cumulostratus, " a blending of cumulus clouds and stratus layers, and " nimbus, " a complex blending of cirriform, cumuliform, and stratiform clouds with sufficient vertical development to produce significant precipitation.
17.
These are, in approximate ascending order of instability or convective activity : " stratiform " sheets; " cirriform " wisps and patches; " stratocumuliform " patches, rolls, and ripples; " cumuliform " heaps and tufts, and " cumulonimbiform " towers that often have complex structures.
18.
These physical types, in approximate ascending order of convective activity, include " stratiform " sheets, " cirriform " wisps and patches, " stratocumuliform " layers ( mainly structured as rolls, ripples, and patches ), " cumuliform " heaps and tufts, and very large " cumulonimbiform " heaps that often show complex structure.
19.
However, he also proposed and had accepted by the permanent committee of the International Meteorological Organization ( IMO ), a forerunner of the present-day World Meteorological Organization ( WMO ), the designation of a new free-convective vertical or multi-�tage genus type, cumulonimbus ( heaped rain cloud ), which would be distinct from cumulus and nimbus and identifiable by its often very complex structure ( frequently including a cirriform top and what are now recognized as multiple accessory clouds ), and its ability to produce thunder.
