“Saharan dust will overtake entire states,” says CNN meteorologist Tyler Mauldin. “Even southern Illinois and Ohio can get into the mix. This is how far it could go north.”
An area of increased pressure over the southeast will allow the Sahara dust layer to move to much of the Gulf Coast region in the coming days.
Portions of Texas, Louisiana, Alabama, and Florida were able to see milky skies and an enhanced sunset tonight.
“The main impacts of Sahara dust will be cloudy skies during the day, reduced local visibility and degraded air quality,” said the Climate Prediction Center. “However, this will also generate very colorful sunrises and sunsets with deeper oranges and reds compared to normal.”
By Friday and Saturday, the dense plume will move throughout the southern United States.
Over the weekend, a thinner amount of dust will advance in much of the eastern United States. At the same time, a denser concentration will be around the Southeast, mainly Alabama, Georgia and Florida.
“Some of this dust will settle at ground level,” says CNN meteorologist Chad Myers. “People should monitor local air quality and possibly limit outdoor exposure.”
This plume of Saharan dust is historical
“It is definitely historical,” Olga Mayol-Bracero, a researcher at the University of Puerto Rico, told CNN Weather. “We knew we were going to be in an extraordinary situation.”
Many of his colleagues across the Caribbean said they have not seen such poor air quality conditions in their entire careers, he said.
Aerosols, measured in PM10, at the Mayol-Bracero research station in northeast Puerto Rico, have never reached the levels they have seen in recent days. The records at this station date back 15 years.
The dust was so dense in Puerto Rico and throughout the Caribbean that it darkened the skies and reduced visibility to just a few miles.
The Saharan dust plume is nothing new. Scientists who study it call it the Saharan air layer or SAL and its effects on the development of hurricanes.
But scientists say this is historical due to the dense concentration of dust.
“While it is normal for dust from the Sahara to reach the United States every hurricane season, this event is unprecedented in thickness and coverage,” says Mauldin.
“Usually, by the time the Sahara dust has traveled so far, much of it has been dispersed and / or deposited in the ocean, so typically this long-range transportation to the Americas would involve much higher concentrations casualties, “Claire Ryder, NERC Independent Researcher at the University of Reading, told CNN Weather.
How the Saharan dust plume began
The initial dust outbreak was fueled by a few smaller storm systems over central and western Africa. Several of these thunderstorms caused large-scale downdrafts and haboobs, or dust storms, to appear. This led to a large amount of dust rising into the atmosphere from the Sahara, Ryder said.
At the same time as these smaller dust storms were occurring, the East African Jet – strong upper winds in the atmosphere that generally transport dust westward – was abnormally weak in June.
This means that a more significant amount of dust could accumulate than usual near the west coast of Africa. It could then be transported west in a very dense cloud when the plane accelerates again.
The Saharan dust layer has paused the hurricane season
For a hurricane, dust in the Sahara is nothing more than extremely dry air. And hurricanes hate dry air; They need a warm, humid and calm environment.
“Dust is the visible part of the area of reduced tropical development potential,” explains Myers. “Dry air and additional vertical wind shear along with dust are the factors driving the limitation of tropical storm development.”
Vertical wind shear is the change in wind speed and direction with height. For a hurricane to form, it needs little or no wind shear and a very humid atmosphere.