isolated cumulus clouds that were not precipitating. The droplets were very small, ranging down to around 5 micrometres in diameter. Although smaller droplets may have been present, the measurements were not sensitive enough to detect them. The smallest droplets were found in the lower portions of the clouds, with the percentage of large droplets (around 20 to 30 micrometres) rising dramatically in the upper regions of the cloud. The droplet size distribution was slightly bimodal in nature, with peaks at the small and large droplet sizes and a slight trough in the intermediate size range. The skew was roughly neutral. Furthermore, large droplet size is roughly inversely proportional to the droplet concentration per unit volume of air. In places, cumulus clouds can have "holes" where there are no water droplets. These can occur when winds tear the cloud and incorporate the environmental air or when strong downdrafts evaporate the water. Subforms Cumulus clouds come in four distinct species, cumulus humilis, mediocris, congestus, and fractus. These species may be arranged into the variety, cumulus radiatus; and may be accompanied by up to seven supplementary features, cumulus pileus, velum, virga, praecipitatio, arcus, pannus, and tuba. The species Cumulus fractus is ragged in appearance and can form in clear air as a precursor to cumulus humilis and larger cumulus species-types; or it can form in precipitation as the supplementary feature pannus (also called scud) which can also include stratus fractus of bad weather. Cumulus humilis clouds look like puffy, flattened shapes. Cumulus mediocris clouds look similar, except that they have some vertical development. Cumulus congestus clouds have a cauliflower-like structure and tower high into the atmosphere, hence their alternate name "towering cumulus". The variety Cumulus radiatus forms in radial bands called cloud streets and can comprise any of the four species of cumulus. Cumulus supplementary features are most commonly seen with the species congestus. Cumulus virga clouds are cumulus clouds producing virga (precipitation that evaporates while aloft), and cumulus praecipitatio produce precipitation that reaches the Earth's surface. Cumulus pannus comprise shredded clouds that normally appear beneath the parent cumulus cloud during precipitation. Cumulus arcus clouds have a gust front, and cumulus tuba clouds have funnel clouds or tornadoes. Cumulus pileus clouds refer to cumulus clouds that have grown so rapidly as to force the formation of pileus over the top of the cloud. Cumulus velum clouds have an ice crystal veil over the