Plume of Saharan dust may dry out South Florida… at least a little


A gritty drifter from a distant desert is ambling west, offering South Florida a potential respite late this week from a spat of wild weather and persistent rain.

Saharan dust, which travels on swift summer breezes miles above the Earth, has already enveloped Puerto Rico and Hispaniola, and could reach Palm Beach County on Friday.

It is the first Saharan dust plume of the season, and while it is not particularly robust, meteorologists said it could be enough to temper rain chances Friday into Saturday.

VIDEO: Storms whip up waterspouts in the Keys

“It’s still uncertain how much we’re going to get,” said Andrew Hagen, a meteorologist with the National Weather Service in Miami. “But in West Palm Beach, the metro areas have only a 30 to 40 percent chance of rain on Friday, which is lower than the last several days.”

READ: Saharan dust makes for surreal South Florida sunrises

The incoming Saharan dust was mentioned by forecasters in Miami and meteorologists at the South Florida Water Management District, who said the far southern reaches of the Peninsula may benefit the most from the traveling particulates of clay that are expected to reduce the rain coverage “considerably.”

This week, South Florida has experienced multiple funnel clouds, lightning strikes that hit a man in Margate and ripped a hole in a Jupiter roof, and nearly 3.5 inches of rain in an hour in a suburban Lake Worth community.

Since June 1, coastal areas of Palm Beach County have averaged 4.3 inches of rain, according to water 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 averaged 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.”

Check The Palm Beach Post radar map

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.

Related: Why South Florida’s thunderstorms have been so intense

Because there’s little open ocean to disperse the dust between Puerto Rico and South Florida, Dunion expects the same high altitude dry air the island experienced Wednesday to be over South Florida sometime on Friday.

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. 

For South Florida, the tentative dust-induced rain break isn’t expected to last long.

Hagen said rain chances pick up again Sunday.

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