A cloud of Saharan dust over the Caribbean on Wednesday is expected to drift into South Florida as early as Wednesday night, spreading across the state on Thursday and bringing drier weather after several days of rain.
The dry air and dust, known as the Saharan Air Layer, have traveled more than 5,000 miles from North Africa as a discernible mass that even someone without a degree in meteorology could identify on satellite. The plume is expected to fall apart in coming days, with some dust moving into the southeast Atlantic Ocean, potentially grazing Georgia and South Carolina, and some scattering across the Gulf, likely filtering into as far as Texas by Friday and into the weekend.
“It’s just south of the tip of Florida right now, over the Bahamas,” George Rizzuto, a meteorologist with the National Weather Service office in Miami, said Wednesday morning. “We’ll see that ramp up over South Florida in the next 18 to 24 hours.”
When the plume arrives in Florida, Mr. Rizzuto said, it will dry out the atmosphere and prevent storms from developing. This drier weather will come after three days of heavy rain in Florida.
The dust is lifted off the Sahara by winds.
The Saharan Air Layer forms when winds lift sand and minerals from the Sahara in North Africa into the atmosphere. It then gets whisked away by a strong wind current, which sometimes pushes it north into Europe, but more commonly carries it west across the Atlantic Ocean. It usually reaches the Caribbean and the Gulf Coast region several times a year.
The dust events occur year-round but are most common from about mid-May into August, usually peaking mid-June to July.
Earlier forecasts had indicated that a cloud of dust would travel from the Caribbean into the Gulf Coast region, but on Wednesday a weather system off the coast of Florida appeared likely to disrupt and diffuse the dust plume.
“It was looking like we were going to get a big slug of dust along the Gulf Coast, now that has trended more toward Florida, Georgia and South Carolina,” said Paul Miller, an assistant professor of coastal meteorology at Louisiana State University. “It looks like the heaviest dust is going to remain offshore.”
Mr. Miller said a ribbon of dust was still expected to push into Louisiana and southeast Texas, most likely Friday night into Saturday.
Houston is expected to see impacts by Friday afternoon and evening and continuing into the weekend. “Still expecting the main impacts to be hazy skies during the day and a decrease in air quality,” said Jimmy Fowler, a meteorologist with the Weather Service.
Coastal areas of Mississippi and Alabama may also see some dust.
Over Puerto Rico, the dust looked like a ‘huge fog.’
On its journey east, the curtain of dust shrouded skies over Puerto Rico Saturday night into Tuesday.
Skies were hazy, and visibility at Luis Muñoz Marín International Airport dropped to five miles. Air quality levels dropped.
Sara Barcelo, who leads walking tours of Old San Juan, said the dust looked like a “huge fog.”
“Puerto Rico is covered in mountains, so something that happens is you can’t see the mountains,” Ms. Barcelo said. “You don’t see the view clearly.”
Ms. Barcelo called the dust typical for this time of year, and said it usually affected air quality and visibility several times in late spring into summer.
By Wednesday, the clear skies had returned over Puerto Rico, but more dust could be on the way with another plume extending off the west coast of North Africa.
“We may have another event during this upcoming weekend, but it’s not going to be as intense as this one,” said Ian Colon-Pagan, a meteorologist at the Weather Service office in San Juan.
Amy Graff is a Times reporter covering weather, wildfires and earthquakes.
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