Periodic Saharan dust outbreaks are not terribly unusual, but it is rare for such episodes to be this widespread or intense. In addition to dark skies, sand can accompany precipitation in some places, creating a rain of grainy mud.

By early Thursday, there is a chance that a dust filament could meander its wall to the Arctic.

The dust in question has origins throughout Central Africa, between Mali, Chad, Algeria and Sudan. Further south, the arid desert of Africa turns into a strip of lush greenery. Part of it is even classified as tropical forest. It falls squarely below the Intertropical Convergence Zone, or ITCZ ​​- a belt of convergent winds that winds around the equator and dumps heavy rain all year round.

The dust in North Africa is not like the sand found on a beach. It is light and powdery, similar in texture to makeup. This facilitates the loft in the atmosphere. Strong trade winds have even carried it across the Atlantic before, yellowing sunsets in Florida, Louisiana and the Gulf Coast.

In June 2020, an outbreak of Saharan dust degraded air quality from Puerto Rico to Dallas, posing a hazard to sensitive groups while simultaneously changing the color of sunlight.

This time the dust is being carried north rather than west by a strong low pressure system west of the Iberian Peninsula, making its way over Norway, Sweden and Finland before dissipating.

A satellite image obtained by NASA on Tuesday shows a counterclockwise whirlpool off Rabat, Morocco. It is the center of low surface pressure. Ahead of the low, southerly winds carried a tongue of dust that swirled northwest around the center of the low. Thick dust clouds can be seen over Portugal, Spain and France.

The Associated Press reported high dust concentrations lowered Spain’s air quality index to “extremely unfavourable” – its lowest rating.

Estimates from computer models suggest that at the core of the plume, dust loads embedded in the column are equal to approximately 5 grams per square meter. In other words, if you could take a square column of atmosphere 1 meter by 1 meter in diameter and expand it into space, you would remove about 5 grams of dust from it. This is equivalent to the weight of two pennies.

Skiers in Austria and Switzerland would have encountered brown snow – snow which, thanks to a strong flow from the south, was covered with a thin layer of dust from the Sahara. The same has been reported in the French Pyrenees. In London, vehicles were splashed by muddy rain.

On Thursday morning, computer models indicate that the skies over Germany will be filled with dust, which will move over Italy, the Czech Republic and Poland in the afternoon. Some dust will even reach the Arctic Circle but will quickly dissolve and become diffuse. Rain in southern Norway can help “catch” some of the dust aerosols in the air. Isolated showers over the Mediterranean Sea can also remove some dust from the atmosphere.

Meteorologists commonly use satellites to monitor the SAL, or Saharan Air Layer, in summer. The dust acts as a tracer that marks the presence of mid-level warm air, which can suppress thunderstorm growth and reduce the chances of tropical cyclones or hurricanes.

Indications suggest dust could linger over eastern Spain through the weekend.

Below, find more scenes from the dust of Europe: