Entry : 7 The 27 Cloud Forms August 26, 2011 By Raymond Antony. This report introduces the 27 cloud form codes in the three main categories determined by cloud type and base height. It shows the diversity of form that the four main cloud types produce when subjected to variants such as; altitude, pressure, wind, wind shear, temperature, humidity, dust / smoke, virticle development, etc. There are many cloud forms that appear due to changing weather or environmental conditions such as cold fronts or troughs. And some from topographical conditions such as warm seas or mountain ranges. They are all made up of the main series of clouds and have their own particular features. They have been given codes to abbreviate there description. These codes are used in reporting the cloud conditions prevalent at the time. The height of a cloud refers to how height the base of the cloud is from the surface. Traditionally clouds are named using Latin words; Latin Root....Meaning Cumulus..... Heap Stratus..... Layer Cirrus.... Curl of Hair Nimbus.... Rain Bottom Layer clouds; Bottom layer clouds can be as low as the surface appearing as fog and some have a base starting at 2,000 meters. Low level clouds are composed mostly of water droplets and occasionally ice in the form of sleet, snow or hail. There are situations whereby the local height of clouds may be effected by Altitude and Latitude. Cb 9 Cumulonimbus With fibrous cirri form top, often anvil shaped. Cb 3 Cumulonimbus Without anvil or fibrous cirri form top. Sc 4 Stratocumulus Formed from the spreading out of Cumulus. Cu 2 Large Cumulus. Cumulus with much more height and overall size. Cu 1 Fine weather Cumulus, Small clouds with little vertical development. Sc 5 Stratocumulus not formed from the spreading out of Cumulus. St 6 Stratus and/or Fractostratus (but not Fractostratus of bad weather) St 7 Fractostratus or Fractocumulus of bad weather. Middle Layer Clouds. Middle layer clouds form at about 2,000 to 6,000 meters and are mostly composed of water droplets with increasing amounts of ice at higher altitudes. Ac 9 Altocumulus of a chaotic sky, generally at different levels. Ac 8 Altocumulus in form of Cumuliform tufts, or Altocumulus with turrets. Ac 6 Altocumulus formed from the spreading out of Cumulus. Ac 5 Thin Altocumulus in bands, or a layer, gradually spreading over the sky and thickening. Ac 4 Thin Altocumulus in patches, often lens shaped and at different levels. Ac 7 Thick layer of Altocumulus. Ac 3 Thin Altocumulus (at a single level) As 2 Thick Altostratus, Sun or Moon invisible (no halo) As 1 Thin Altostratus, semi transparent (no halo) Ns Nimbostratus High Layer Clouds. High layer Clouds are composed largely of ice with some water droplets. Heights range from 6,000 meters to above 20,000 meters. These clouds are usually thin and wispy with ill defined edges. Cc 9 Cirrocumulus. Cs 7 Veil of Cirrostratus covering the whole sky (halo often visible) Cs 8 Cirrostratus not increasing from the horizon and not covering the whole sky. Cs 6 Cirrostratus increasing and thickening, the continuous veil exceeding 45deg above the horizon. Cs 5 Cirrostratus, increasing and thickening, the continuous veil not exceeding 45deg above the horizon. Ci 4 Cirrus, often hook shaped, gradually spreading over the whole sky and thickening. Ci 3 Dense Cirrus, often anvil shaped, being the remains of the upper part of Cumulonimbus. Ci 2 Dense Cirrus in patches or twisted masses, not increasing. Ci 1 Filaments, strands or hooks of Cirrus. When I was learning how to do the current weather reports, these tables along with photographic examples made the task so much easier. In fact a lot of what I do in my job is not so mentally taxing. I just have to pay strict attention to the details. It is all about accuracy and consistency that makes a; reliable, useful report. … [Read more...]
