The Hats of Mount Fuji
Smooth, saucer-shaped clouds settle over Mount Fuji like hats, and clouds like them are often reported as UFOs.
What was reported
Mount Fuji often wears a 'hat': a smooth, layered cloud, called kasagumo in Japanese, sitting on or just above the summit. Nearby, lens-shaped clouds called tsurushigumo can hang in the sky without moving for hours.
Around the world, lenticular clouds like these, sharp-edged and saucer-shaped, are among the things most often reported as flying saucers.
Explanations offered
They form when moist air flowing over a mountain rises and cools, condensing into cloud, then sinks and warms again on the far side, where the cloud evaporates. Because the air flows through while the cloud stays put, they can look solid and stationary. Local weather lore says a hat on Fuji means rain is coming.
- When
- Ongoing
- Where
- Mount Fuji, Shizuoka and Yamanashi, Japan
- Witnesses
- Photographers and people living around the mountain
- Status
- Explained
Famous cases are real, widely reported events. Each file sets out what witnesses said and the explanations that have been offered, without taking a side.