Persistent contrails (Cirrus homogenitus) may be observed, over a period of time and under the influence of strong upper winds, to grow and spread out over a larger portion of sky, and undergo internal transformation such that the cloud eventually takes on the appearance of more natural cirri-form clouds. In this instance, the resulting clouds will be given the name of the appropriate genus (for example, Cirrus, Cirrocumulus, or Cirrostratus) followed by any appropriate species, variety and supplementary features, followed by the special cloud name “homomutatus”, (for example, Cirrus floccus homomutatus or Cirrus fibratus homomutatus).