Mt Fuji with a sedge hat or sugegasa [菅笠].
This is an example of a lenticular cloud, also known as altocumulus standing lenticularis. These are stationary, lens-shaped clouds that are formed at high altitudes. They are included in the middle layer cloud family because the bases of the clouds are stationed between about 2,000 and 7,000 meters.
These clouds form when moist air is forced to flow up around mountains and large hills. The water is super cooled and condensed from air below the dew point temperature.