A massive plume of Saharan dust is making its way across the Atlantic offering South Florida a potential break in the endless days of rain, humidity and thunderstorms.
The dust, clearly visible on GOES-East satellite images, reached the Turks and Caicos and southeastern Bahamas this morning, according to the National Weather Service in Miami.
While a mat of moist air flows stubbornly high in the atmosphere, NWS meteorologist Andrew Hagen said the Saharan dust is lower down, existing between 5,000 and 15,000 feet, which will help decrease rain chances Friday and Saturday.
“On average per year we have about two pretty good SAL (Saharan air layer) events, but this looks like only a little bit of the SAL will make it over South Florida on Friday,” Hagen said. “When it’s strong, there’s a milkiness to the sky and sometimes you even see particles on cars.”
While this may not be a strong Saharan dust event, it will keep rain chances Friday and Saturday below 50 percent in the metro areas of Palm Beach County, Hagen said.
“The SAL is playing some role there,” he said.
Since June 1, coastal areas of Palm Beach County have averaged 4.3 inches of rain, according to district gauges. That’s 1.1 inches above what’s normal for the second week in June and adds to the whopping 15.3 inches of rain the area got in May.
For the 16-county region managed by the district, May rainfall totaled 11.45 inches, about 7 inches above normal.
“This is the third year in a row Mother Nature has dealt us a bad hand and brought us an extreme beginning to the wet season,” said district Chief Engineer John Mitnik during a press conference last week on how the district is handling all the water. “May brought more than 300 percent of above normal rainfall.”
Jason Dunion, a meteorologist with the University of Miami who tracks Saharan dust, said weather balloons launched from Puerto Rico on Wednesday showed the air 1 to 3 miles into the atmosphere was up to 50 percent dryer than what would be expected because of the Saharan air layer, or SAL.
A Saharan air layer is made up of sand and mineral particles that are swept up from 3.5 million square miles of desert and carried by air currents 4,000 miles west across the Atlantic. The largest plumes can be the size of the continental U.S., and while June is the beginning of the Saharan dust season, the most potent plumes appear in July and August.
That’s when large thunderstorms start a march across Africa, south of the Saharan desert, and sweep dust high into the atmosphere before spinning it out over the Atlantic with easterly waves that can form hurricanes.
“That tropical wave season starts to ramp up in July and August and we think there is a link between it and when we see the Saharan air layer get bigger and much more far reaching,” said Dunion, who is also a research scientist with NOAA’s Hurricane Research Division.
There still could be soupy humid air at the surface, but clouds typically collapse once they hit the Saharan air layer.
“It tends to stifle thunderstorms, and could be a little warmer because it will clear out the clouds,” Dunion said.
This year, Dunion is tracking the Saharan dust with the supercharged GOES-East weather satellite that was launched in November 2016.
It carries the Advanced Baseline Imager — a 16-channel camera built by the Melbourne-based Harris Corp. The previous satellite had just five channels. Combining two infrared channels from GOES-East gives researchers a better image of the Saharan dust, and one that crosses the Atlantic from Africa into the Gulf of Mexico.