A giant plume of Saharan dust on a 5,000-mile journey is expected to drift across the southeastern United States this week at altitudes between 20,000 and 30,000 feet, bringing enhanced sunrises and potentially suppressing storm formation.
“Due to more sunlight being scattered by the dust particles, there will likely be more vibrant sunsets and sunrises of the orange and red side of the visible light spectrum,” said David Wally, a meteorologist with the National Weather Service office in Upton, N.Y.
But the dust plume also could have effects on certain health problems.
“This can be an allergen that is uncomfortable with asthma or reactive airways,” Dr. Sandro Galea, dean of the Boston University School of Public Health, said on Monday. He suggested that people monitor the “level of air particles in their area and take precautions in working or being outside as this passes through.”
Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City, also said on Monday that “particulate matter of this dust cloud contains more silica, and is a hazard to those with underlying lung conditions. But even normal healthy people are subject to irritant effects.”
He recommended wearing masks and using air filters, as well as avoiding outdoor activities.
Satellite images from the past few days show the thick dust as a brown mass moving off the west coast of Africa, crawling across the Atlantic and then drifting over the eastern Caribbean on Sunday. The mass is expected to arrive in the Gulf Coast states, including Texas and Louisiana, on Wednesday and Thursday.
Because it is a dry layer of air, the dust helps suppress the development of tropical systems, according to the National Weather Service.
“The dry nature of the air mass that originates from the Sahara limits thunderstorm and cloud development, which are needed for the development of tropical cyclones,” Mr. Wally said.
“It’s not a long-term effect, but for the short term, it’s a plus,” he added. He also noted that it is still early in the hurricane season, which runs from June 1 through Nov. 30.
The arrival of the Saharan dust cloud is not unusual and happens a few times year, said Mr. Wally, who added that the plumes are usually short-lived, lasting no more than a week.
The episodes often take place from late spring to early fall, “when you have easterly trade winds that dominate across the tropics, and sometimes those can extend deep into the atmosphere,” he said.
During a dust cloud last year, people posted photos of vibrant sunsets on social media. In one photo, from Jupiter, Fla., Steve Weagle, the chief meteorologist for WPTV, described a bright pink and yellow sunset as a “fire in the sky.”
In addition to vibrant sunsets, people can expect their usually bright blue skies to have a more milky, hazy appearance, Mr. Wally said. But, he added, “I don’t think you would be looking at a brown sky.”
On Sunday, Puerto Rico’s Department of Health also said that people who have asthma, respiratory illnesses and allergies, “as well as those who have been infected with Covid-19, must be very careful not to aggravate their health conditions.” Ibis Montalvo Félix, a manager for the department’s asthma program, said that the dust is expected to cover the island this week.
She explained that the dust from the Sahara is “bringing a mass of hot air, with very little humidity, which in turn contains biological and chemical materials that are potentially harmful to respiratory health. This phenomenon, an annual recurrence on the island, is considered an environmental trigger for asthma symptoms.”