Aliens, Scotch bonnet and pink straw boater.

These are just some of the speculations on the nature of the strange pink wisp floating over Skye on Wednesday evening.

At the risk of disappointing any tinfoil-wearing conspiracy theorists, aliens are not among us. In fact, the rare sighting is a lenticular cloud which was photographed as it hung over Portree.

The image sparked a flood of comments online when Helen Wilson posted it on the Scotland from the Roadside Facebook page.

The elliptical-cylindrical shape forms when strong, moist winds blow over rough terrain, such as mountains or valleys.

But Scots had other ideas when it came to defining the weather phenomenon.

"UFO" was a common theme, along with "flying saucer" and "cloud halo", but some took a more innovative approach.

One Facebook user thought the cloud resembled a "Scotch bonnet" while another thought it was the hat belonging to the Swedish chef from The Muppets.

But while Scots chose to poke fun at the formation, the clouds are commonly referred to as "UFO clouds" because they are so commonly mistaken for alien invasions.

STV weather presenter Sean Batty says: "The full name of this cloud is altocumulus lenticularis, which are fairly common in Scotland, thanks to our mountains. Yesterday's cloud sitting over Portree looks as if it was sitting at around 10,000ft.

"They form downwind of mountains when conditions are right. As air flows over mountains it is disrupted and becomes turbulent on the leeward slopes and the air begins to undulate. Air flows in the same way as water does, and if you think of a river or stream, you'll sometimes see that as the water comes into contact with rocks in the river-bed the water spins in swirls, called eddies.

"Lenticular clouds form in the wave crest of the undulating air eddies 'downstream' of the mountains, which is why they sometimes form into swirls, a bit like a Walnut Whip. They can form up to 60 miles downwind of the mountain chain that started the wave motion.

"Over the years I've seen lots of examples of these from across Scotland. As they form downwind of the mountains, the most common areas for these are generally around Moray, Easter Ross, Aberdeenshire and Angus, as westerly and south westerly winds are more common in Scotland.

"When there is a northerly wind, these clouds will sometimes be seen around the central lowlands. In this case, over the last few days the wind has been coming from the north east or east, which means the most likely areas to see lenticulars is around the Hebrides and the west Highlands.

"With another easterly flow today, it's likely lenticular clouds could again be spotted in the sunnier parts of the west."