A massive cloud of dust traveling from Africa across the Atlantic Ocean toward the U.S.—known as a “Saharan Dust Plume”—is expected to make landfall this week across the southeastern U.S. states, descending like a thick gray cloud or haze over land and making sunsets appear even more vivid.
The dust—called the Saharan Air Layer (SAL) by meteorologists—is a mass of dry and dusty air that forms in the Sahara Desert in the spring, summer and early fall and moves over the tropical North Atlantic, according to the U.S. National Ocean and Atmospheric Administration.
Dust plumes from the Sahara are normal for this time of year, though the one that started in western Africa last weekend is making headlines as one of the most extreme in recent history, appearing much clearer in satellite imagery than others due to its massive size, reports CBS.
This plume is expected to hit the Gulf of Mexico and parts of the U.S., including Texas and Florida, beginning Wednesday after surging across the Atlantic Ocean and Caribbean Sea last weekend.
The main impact will be particularly colorful sunrises and sunsets, according to the National Weather Service, as well as hazy skies.
The plume, which is composed of dry air, acts as a hurricane repellent since hurricanes need hot and humid conditions in order to form, according to CNN; the plume could mean fewer tropical storms so long as the SAL sticks around.
Here’s what this SAL looks like:
Those with dust allergies or respiratory issues may experience heightened symptoms due to the massive amount of dust in the air. The Barbados Meteorological Services issued a “severe dust haze” warning, advising those with dust allergies or respiratory issues to travel with prescribed medications as a precaution.
Though scientists have yet to explain this SAL’s enormity, dust plumes are a normal weather phenomenon for this time of year. The dust plumes originate from strong winds in the Sahara Desert, which blow through the Intertropical Convergence Zone in the Atlantic near the Cape Verde Islands, getting carried massive distances by the east-to-west trade winds. They usually diffuse near or at the Caribbean—another reason for the attention on this plume.
After making landfall in the Caribbean in the last few days, local authorities are advising those with dust allergies and respiratory issues to take caution; a meteorologist tweeted this picture of haze in Antigua.
The Saharan Air Layer (U.S. National Ocean and Atmospheric Administration)