Strange cloud looks like 'alien mother ship', why should we take shelter immediately?

A cloud - or perhaps a whole cloud because it was so large - grey, strange and mysterious looking, appeared in the sky over Spain.

Many people commented that this cloud looks very scary, shaped like an alien 'mothership' . What do experts advise us when we see this phenomenon?

Everyone knows that clouds can come in many shapes, however, seeing a giant cloud with a strange shape and gray color can still be scary for many people.

Recently, a strange cloud appeared in the sky in the Balearic Islands (Spain). This cloud is extremely large, covering an entire area, dark gray in color and looks half like ocean waves, half like some kind of machine in the sky. Therefore, many netizens call this cloud the 'alien mother ship' ('mother ship' usually refers to a large, powerful ship that supports or coordinates the activities of smaller ships).

Many people call this cloud the "mother ship". (Photo: Rafel Ginard).

But in fact, this cloud has nothing to do with aliens.

These strange clouds are called shelf clouds (also called 'tsunami clouds' because in many cases they look like tsunamis in the sky). These clouds appear to be quite low and are often very large, covering an entire area of ​​the sky, blocking out most of the sun , according to The Des Moines Register .

Shelf clouds often block out light over large areas, making them truly terrifying to look at. (Photo: NWS).

Shelf clouds can form in the path of a series of thunderstorms, so they can be considered a precursor to thunderstorms (but not necessarily a cause of them) , according to a National Weather Service (NWS) meteorologist. They often form when the air ahead of a thunderstorm meets the cooler air that comes with rain in that storm. Shelf clouds can also form at the edge of a cold air mass.

Super shelf cloud in Queensland (Australia). (Photo: Jenneal100).

Because shelf clouds often appear before thunderstorms - with heavy rain and strong winds, seeing them can also be scary. Meteorologists advise that when shelf clouds are approaching, people should quickly arrange their work to find shelter, avoiding staying outdoors for long .