The observed cloud groups, up to four may be included.<br /></p><p><br /></p><p>When cumulonimbus clouds or towering cumulus clouds are detected by the automatic observing system and the cloud amount and the height of cloud base cannot be observed ("//////") this is indicated by a missing cloud layer with a nil reason of either notObservable if the value could not be observed due to a sensor or system failure, or notDetectedByAutoSystem if the automated system is working properly but did not observe any values<br /></p>