An enormous plume of dust and dry air from the Sahara Desert hit Florida on Thursday, and it's expected to spread to other Gulf states.
Experts have nicknamed the plume the "Godzilla dust cloud." It crossed the Atlantic over the last 10 days.
The dust cloud brings hazy skies and reduced visibility and can also severely lower air quality.
Health officials advise people to wear masks and stay home, especially if they have asthma and allergies.
A monstrous cloud of dust reached Florida on Thursday, and it's poised to engulf the southeastern US this weekend.
Some experts have nicknamed it the "Godzilla dust cloud." But it's more commonly known as the Saharan air layer (SAL) — a plume of warm, dry air peppered with dust and sand that travels thousands of miles west across the Atlantic Ocean from above the Sahara Desert.
On Monday and Tuesday, the cloud smothered Cuba, Jamaica, and Puerto Rico before making its way to the Mexican coast. Skies there dimmed as the suspended dust blotted out the sun. Local health authorities urged Caribbean island residents to remain indoors and wear masks, since the dust cloud reduced air quality to unhealthy levels, Reuters reported.
By Wednesday afternoon, the plume had seeped into most of the air above the Gulf of Mexico. A Thursday morning National Weather Service forecast suggested the Saharan dust would arrive over Gulf Coast states "over the next couple of days."
—NWS Eastern Region (@NWSEastern) June 24, 2020
According to meteorologist Jeff Beamish, the plume could "potentially spread into the central and eastern US by Saturday."
NWS experts said the dust will bring redder sunsets, but also "hazy skies during the day, locally reduced visibility, and degraded air quality."
'The worst I've seen since we've kept records'
This isn't the first time the SAL has crossed the Atlantic. The mass of warm, dusty air forms annually and sits over the Sahara from late spring to early fall. Every three to five days between late June and mid-August, part of the air mass breaks away, shoved west by strong, tropical winds.
The SAL doesn't always make it the full 5,000 miles across the ocean, but winds sometimes send the dust-containing cloud as far west as Texas, according to the National Oceanic and Atmospheric Administration (NOAA).
Medios y Media/Getty
This particular dust plume, however, is one of the largest — and dustiest — ever recorded.
"It's the worst I've seen since we've kept records," Evan Thompson, director of the meteorological service division in Jamaica, told Reuters. "We are seeing a much thicker mass of dust particles suspended. It is a lot more distinct and noticeable."
The dust lowers air quality and is linked to breathing problems
Pablo Méndez Lázaro, an environmental health specialist at the University of Puerto Rico, told the Associated Press that this Godzilla dust cloud "is the most significant event in the past 50 years," adding that "conditions are dangerous in many Caribbean islands."
The SAL's dust particles and sand led air quality in Puerto Rico and nearby islands to drop to hazardous levels, the AP reported.
Officials have encouraged people across the Caribbean to wear masks and stay home, especially if they have a respiratory condition.
"The tiny dust particles contained in the plume will cause eye, nose and throat irritation for anyone who comes in their path, but particularly for allergy and asthma sufferers," Dr. J. Allen Meadows, president of the American College of Allergy, Asthma and Immunology, said in a statement on Tuesday.
He added dust clouds like this "can make asthma symptoms worse and make breathing more difficult."
Like the guidance in the Caribbean, Meadows and other US experts recommend that Americans with asthma and allergies wear masks and stay indoors as much as possible.
The SAL dust plume isn't all bad
While the prospect of hazy skies and choking dust is certainly unpleasant, the SAL plume has some benefits.
When it escapes the Sahara, the SAL settles into a 2-mile-thick layer that bottoms out one mile above the ground. This layer of dry, warm air, propelled by strong winds, can suppress hurricane and tropical storm development in the Atlantic. Hurricanes form when warm moisture rises and creates thunderstorms. But the SAL prevents that moisture from reaching the atmosphere.
According to NOAA, the plume also benefits South American rainforests.
When it crosses the Atlantic, some of the SAL dust can also blow south into the Amazon River Basin, where the minerals in the dust replenish nutrients in rainforest soil.
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