The dusty layer of air could put a welcome, albeit temporary damper on the development of any storm systems in the tropics, but the thick haze could have impacts if and when it arrives in the United States.
At present, the plume of desert dust spans thousands of miles and is slithering across the ocean. Satellites peering down from space captured the coffee-colored veil being drawn over the Atlantic, slowly weaving westward with the tropical west Atlantic in its sights. Projections indicate that the dust could make it to the Caribbean by late this weekend and to the Gulf Coast in about a week.
The dust itself is harmless and will make for brilliantly vibrant sunsets in locations it passes over. However, it may increase the growth of ocean bacteria and, where concentrations are high enough, reduce air quality.
The dust plume now
The billowing dust was wafting west off the coasts of Senegal, Mauritania and Western Sahara on Thursday, reaching more than 1,500 miles into the open Atlantic.
Models indicate that the plume could reach the Leeward Islands and Lesser Antilles by late Thursday or early Friday before a renewed, more concentrated shot of dust moves in over the weekend.
That same model, produced by NASA, calls for dust to make an appearance in Puerto Rico, the Dominican Republic and Haiti between Sunday and Tuesday.
There’s an increasing chance that Cuba and parts of the U.S. Gulf Coast could encounter some high-altitude dust mid- to late next week.
How the dust layer could put a temporary damper on hurricane season
When Saharan dust sneaks across the ocean, it’s a sign of a layer of warm, dry desert air progressing westward. We call that the “Saharan Air Layer,” or SAL.
Hot air at the mid levels can quash thunderstorm development, decreasing the likelihood that tropical storms or hurricanes form in the short term. That’s good news heading into July, though the current dust events will be long since over by the time hurricane season peaks in August and September.
When the dust arrives in the U.S.
Saharan dust can occasionally reach North America, though often in diluted quantities. In concentrations as in the plume forecast to near Puerto Rico, a number of other islands and the Gulf Coast, the effects can be more noticeable.
For starters, the sky may appear hazed over during the day, with an acute brownish tinge possible. Sunsets could appear markedly more vibrant, with deeper, more expansive brushstrokes of orange and yellow washing across the sky.
About a year ago, a plume of Saharan dust intensified sunsets along the Gulf Coast.
There’s even a remote chance that some of the dust becomes entrained in any afternoon thundershowers that bubble up, especially over Puerto Rico, Cuba, and perhaps Florida, toward the middle of next week. That could lead to isolated instances of muddy rain — most visible when sandy raindrops fall and splatter on the hoods of cars.
That happened in the United Kingdom in late April 2019 when a chute of dust was swept north by the jet stream like a conveyor belt.
An outbreak of dust in the Canary Islands was so intense in February that air travel was grounded and schools on the archipelago shuttered as air quality concerns skyrocketed in the autonomous territory of 2 million. The extremely fine particulates can pose a hazard to those with sensitive lungs.
Occasionally, dust that settles in the ocean can promote the growth of various species of bacteria, including vibrio. The metallic compounds contained in the dust provide nourishment for the bacteria, supporting its proliferation. According to the CDC, vibrio are most common between May and October, but can stick around all year in climates where the water is warm enough.
Vibrio are problematic if ingested, primarily associated with undercooked seafood.