Types For Observers has excellent photographs and descriptions of these supplementary features. CLOUD  IDENTIFICATION Since the only method at present to identify cloud type is by visual identification, you must be familiar with the characteristics of the various clouds. Although NAVMETOCCOMINST 3141.2 and NAVMETOC- COMINST 3144.1 present a good description of the clouds present in the 27 states-of-the-sky, you should be thoroughly familiar with the identification features of each cloud type. Let’s take a closer look at some of the important identification features of cloud genera. Cumulus (CU) Cumulus, translated from Latin, means "heap." Heap aptly describes a cumulus cloud in most of its stages. Since cumulus clouds form by convective action, the height of their base above the surface is directly related to the amount of moisture near the surface. The higher the moisture content, the lower the cloud base. Although the water droplets in cumulus are very numerous, they are very small in the cloud’s early stages. As a cumulus cloud continues to grow, the number of large drops within the cloud increases.  These large drops may be precipitated from the cloud or may continue to be suspended by the vertical air currents within the cloud. Precipitation in the form of showers occurs with cumulus clouds of moderate development. Although  this  precipitation  may  be  of  moderate intensity, its duration is usually short lived. These clouds do not produce the heavy rain and high winds that are associated with their bigger brothers, the cumulonimbus. Occasionally,  the  showers  from  cumulus  clouds evaporate before they reach the ground. This situation is known as virga and is characterized by a dark "fuzzy" area immediately below the nearly uniform base of the cumulus cloud. This darker fuzzy area, caused by the precipitation, decreases in intensity beneath the cloud until it disappears (complete evaporation). When virga consists of snow or ice crystals, the virga is not dark and appears  more  "wispy."  This  is  due  to  the  greater influence of the wind on the snow and ice crystals; the precipitation  trails  appear  to  be  bent  by  the  wind. Cumulus clouds produced by convective heating develop in a distinct sequence. This is the primary means by which convective clouds form within an air mass. The cumulus clouds first appear as cumulus humilis, and then develop into cumulus mediocris and cumulus congestus. Although cumulus congestus may continue   to   develop   into   cumulonimbus,   the cumulonimbus  clouds  are  identified  as  a  separate  cloud genus. When  cumulus  clouds  are  formed  by  mechanical lift, the sequence is the same. However, early stages of development  may  not  be  apparent,  especially  if stratiform clouds are already present. CUMULUS HUMILIS.—In the earliest stage of development, cumulus usually forms in, and indicates, good weather. A typical cumulus cloud is shown in figure 1-7 in its formative stage. Point A shows the clearly defined outline, the distinct white color, and the characteristic "bulging" appearance. At point B, notice the characteristic flatter and darker base. In this stage, the cumulus is often called a "fair-weather cumulus" or cumulus humilis. CUMULUS  MEDIOCRIS.—When    cumulus clouds continue to develop vertically, and reach a moderate vertical extent, they are called cumulus mediocris  (fig. 1-8). Cumulus mediocris have small cauliflower-like   buildups,   but   rarely   produce precipitation other than virga. CUMULUS CONGESTUS.—Cumulus  clouds that continue to develop and to reach moderate vertical extent  are  called  cumulus  congestus.  Congestus generally  means  the  sky  is  filled  with  clouds  vertically, rather than horizontally. These clouds are identified by several  layers  of  puffy,  cauliflower-like  buildups Figure 1-7.—Cumulus humilis cloud. 1-9