Saharan dust Q&A: Densest plume in decades bringing hazy, colorful skies to Gulf coast

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TAMPA, Fla. (WFLA) — The densest cloud of Saharan dust we’ve seen in decades has made its way to the Gulf of Mexico after a 5,000-mile trek across the Atlantic Ocean.

But with the arrival of the dust, we’ve also seen an arrival of misinformation swirling online about what it is and what it means. Our Tracking the Tropics team decided to clear up confusion and answer questions about the dust on Thursday.

What is Saharan dust?

The Saharan dust is something we see every year when plumes are generated from strong winds over the Sahara Desert. Winds and updrafts kick up the dry top layer of soil and raise it high into the atmosphere. Easterly trade winds can then carry the dust into the Atlantic. Sometimes, when the dust plume is large enough and the easterly winds are strong enough, the plume travels all the way to the Caribbean and even the United States.

Dust plumes coming off the coast of Africa are quite normal this time of year. The plumes typically begin in mid-June and run through mid-August, peaking somewhere in the middle. According to NOAA, the plumes of dust seem to rapidly subside after mid-August, which is also why we see an uptick in tropical activity in August and September.

Not a dust storm

To avoid confusion and clear up one of the most common misconceptions, this is not a typical dust storm. The dust is suspended high up in the atmosphere, between 5,000 feet and 20,000 feet – or about one to four miles.

What’s different about the plume we’re seeing now?

The dust plume that was visible in several states along the Gulf Coast is the densest we’ve seen in decades. It was visible in several states along the Gulf Coast on Thursday morning.

“It’s much, much denser this time around,” WGNO Chief Meteorologist Hank Allen explained. “It’s probably the biggest we’ve seen in about 50 years or so.”

WFLA Meteorologist Amanda Holly pointed out the plume we’re seeing now is also denser than what we usually see this time of year.

“We typically see the dust coming over from June, July and through mid-August. That’s when the dust is lifted up over the Saharan Desert and it’s brought over

Will I see colorful sunrises and sunsets?

Hazier skies from the plume will lead to exceptionally colorful sunrises and sunsets as the light bends around and through the particulate.

“Sometimes we see get colorful sunrises and sunsets depending on the denseness of the plume,” Holly explained. “If it’s too dense, we actually see the sun turn into kind of a dot, like a little pinhole as it rises and sets.”

Allen says that’s probably what will end up happening in much of the Gulf Coast area because this specific plume is so dense.

“At this point, certainly what we’ve seen this morning, this is so dense you’re ending up with more of a gray, sort of milky shading in the sky which is a lot less attractive than the pretty oranges and pinks,” he said.

Allergy sufferers, beware

Allergy sufferers may notice an increase in irritation from the dust as some of it does mix in closer to the surface.

“We do get some of that dust settling down and it has been known to be a possible irritant to those of you guys who have allergies,” Holly said. “Obviously not something we want to deal with right now…but something to be mindful of as this dust is near.”

Does the dust cause red tide?

NASA is currently studying a link between the dust plumes and red tide. Studies have shown after large plumes arrive, there is an increase in the harmful algae.

So why is that? Mixed in with the dust is iron from the topsoil in Africa. When the iron ends up in the Gulf, it actually fertilizes the water which can begin the process of the toxic algae bloom.

NASA also explained that the “dust helps build beaches in the Caribbean and fertilizes soils in the Amazon.”

What does it mean for hurricane season?

Dust plumes seem to inhibit tropical development thanks to the embedded dry air and strong 25-55 mph mid-level winds along with a few other factors. However, it is important to note that research is ongoing on this topic.

Dust plumes typically begin in mid-June and run through mid-August, peaking somewhere in the middle. According to NOAA, the plumes of dust seem to rapidly subside after mid-August, which is also why we see an uptick in tropical activity in August and September.

How far north will the dust go?

“Some of the modeling actually has this circling all the way back through, riding up the eastern part of the country and, believe it or not, making it all the way over toward the United Kingdom through the next week,” Allen said.

That could happen because of how dense the plume is right now and how nothing is really standing in its way to break it up.

Can the dust produce thunderstorms?

This is something meteorologists have been discussing recently because the dust has 50% drier air than the typical tropical air seen in the Gulf of Mexico.

“You would think that would limit the thunderstorms in the area where the dust is at,” Holly said. “But we’ve got dust right now in most of the Gulf of Mexico and we see plenty of thunderstorms over Houston and we’ve still got rain chances in the forecast.”

The bottom line is thunderstorms can happen where dust is present, but that doesn’t necessarily mean the dust is producing those storms.

How does the dust interact with humidity?

There’s a minimal impact with humidity because the dust layer is so high up.

“The humidity you feel is more at ground level,” Allen said. “So I would say not an interaction but the flow rounding up into the Gulf that is bringing this dust layer is also partly responsible for bringing the flow up in the moisture out of the Gulf.”

How long will the dust last?

We’re expecting the current dust to stick around for at least a week or so. But keep in mind, this is just the first plume we’re tracking.

“There are several others, one still making its way across the Atlantic right now and it looks like another one trying to bubble up again over the Sahara,” Holly said. “So I’m expecting this dust to last until next week. And if it does linger this long, that’s when we maybe start to see some of the dust on our cars.”

Will it affect airline flights?

Our Tracking the Tropics team says probably not because pilots have instrumentation to work around it.

“But it certainly impact airline visibility,” Allen said. “So as opposed to visual flight rules, it’ll be more instrument-based.”

“Planes might actually be above it,” Holly added. “It could make for some interestign photographs.”

Is it safe to swim in the Gulf?

Yes, as it relates to dust. The dust will not have any impacts – at this point – on water quality.

What is the effect of rain on the dust?

While the thunderstorm is happening, some of the dust can be brought down to the surface. After the thunderstorm goes away, there could be a short period of time with cleaner air in the area before more dust starts to move in.

Tracking the Tropics is keeping you informed throughout the hurricane season. Watch live every Wednesday at 2 p.m. ET for an update.

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