Lenticular clouds' distinctive round disc shape has been the cause of many misconceptions, with some people claiming that these clouds are alien spacecraft in disguise. Though it is an exciting thought, the reality is that it is just another case of unusual weather. Also, dubbed Altocumulus Standing Lenticularis clouds, these clouds tend to form around large protruding landmasses like hills or mountains. When stable, moist air flows over a mountain, a series of oscillating waves are created. If the temperature at the crest of the wave is the same as the dew point temperature, condensation occurs in a lens formation. As the air through the trough of the wave, where the temperature and dew point temperature are not equal, evaporation occurs and a series of lenticular clouds may form.