A Gigantic Cloud of Saharan Dust Is Barreling Toward Florida

Gizmodo

3 days ago

An enormous cloud of dust from the Sahara is floating westward over the Atlantic Ocean, heading straight for Florida.
The densest part of the African dust plume has already reached the Caribbean and could blow into the Sunshine State by midweek, according to the National Weather Service office in Miami. When the dust rolls in, it will likely lead to drier local weather, diminished air quality, and exceptionally vivid sunrises and sunsets, meteorologists say.
Around 1 p.m. on Monday, the NWS office in San Juan, Puerto Rico said that peak concentrations of Sahara dust were rolling into the area and were expected to arrive within the afternoon. The agency has issued multiple air quality alerts, as inhaling dust can irritate respiratory systems and worsen allergies, asthma, and other respiratory conditions.
These particles can also trap heat near the ground, and as such, NWS San Juan has issued a heat advisory that will remain in effect through Tuesday. Southeasterly winds combined with the effects of the dust cloud are expected to keep temperatures above normal in many coastal and urban areas, the agency stated.
At the end of last week, a thin veil of dust was already dispersing over Florida, NWS Miami meteorologist Ana Torres-Vazquez told Scientific American. By midweek, a thicker, denser plume will billow into the state, though meteorologists expect it will be patchier than the current conditions in the Caribbean. Some patches of dust could reach the rest of the Gulf Coast by late this week, according to The Weather Channel.
Formally known as the Saharan Air Layer, or SAL, this mass of extremely dry, dusty air forms over northern Africa each year from late spring to early fall, according to NOAA's Atlantic Oceanographic & Meteorological Laboratory. It's created by ripples in the lower-to-middle atmosphere—called tropical waves—that track along the southern edge of the Sahara Desert and waft massive amounts of dust up into the atmosphere, Jason Dunion, a NOAA meteorologist, explained in a 2020 interview.
Every three to five days, the SAL moves over the tropical North Atlantic Ocean in what's known as an 'outbreak.' This activity typically peaks from late June to mid-August, and during the peak period, outbreaks stretch farther west. Once or twice a summer, an SAL travels more than 5,000 miles to the Gulf Coast, blowing across states from Florida to Texas. That's precisely what's happening now, according to NOAA, which tracks the SAL using its GOES-16 satellite.
The arrival of this SAL happens to coincide with the start of the Atlantic hurricane season, which officially began on Sunday, June 1. The warmth, dryness, and strong winds associated with this mass of dusty air have been shown to suppress tropical cyclone formation and intensification, according to Dunion. Thus, the SAL typically prevents hurricanes from taking shape.
But despite this, meteorologists are already monitoring an area along the southeast coast for potential subtropical or tropical development. AccuWeather predicts that, over the next 10 days, dry air from the SAL will alternate with moist air over the Caribbean and off the coast of Florida.
This may cause a zone of moisture to develop from South Florida to the Bahamas and Cuba early this week, potentially bringing several inches of rain and thunderstorms to the region. While the risk of tropical development is low, heavy rain could result in minor coastal flooding, rip currents, and rough surf by mid-to-late week, AccuWeather reports.
On the bright side, Florida residents—and potentially those in other Gulf Coast states—can expect to see some especially breathtaking sunrises and sunsets this week, thanks to the SAL. That's because high concentrations of airborne dust enhance the bright red and orange hues that result from low-angle sunlight passing through the atmosphere, according to NOAA.
The SAL could linger over the southeast for several days, though it's unclear when the dust will begin to dissipate. Meteorologists will be watching closely to see how its presence impacts air quality, visibility, and the early days of hurricane season.