It is the level of importance that is placed on the elements that must be understood. Unfortunately, cloud reports are often one of the least satisfactory items in the surface report. Usually clouds cannot be measured, but must be estimated. The present codes do not permit an observer to describe properly the various states of the sky found in low latitudes. The observer s entry nearly always entails some arbitrary decision.
Some observers regularly transmit the same combination of low, middle, and high clouds.
In spite of these drawbacks, much can be extracted from the cloud data. Emphasis must be placed on the presence or absence of low, middle, or high clouds as groups. Division into one of nine types within each group should generally be disregarded, especially with reference to middle and high clouds. Cumulus is the predominant type of cloud found in the tropics. There are many signifi-cant types of cumulus, and they usually range in some intermediate form between cumulus humilis and cumulus congestus.