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cloud Saharan

Saharan dust cloud cloaks U.S. Gulf Coast in choking haze – CBS News

Massive dust cloud to reach the U.S.

What’s been called the most significant dust cloud in 50 years has now shrouded the U.S. Gulf Coast in a thick, dusty haze. The dust layer, which originated in the Sahara desert and drifted across the Atlantic, is forecast to continue moving north and east through the weekend, impacting areas from Texas and Florida all the way up to as far north as the Canadian border.

For most people, the dust will merely be a nuisance, but for many who have breathing issues the extra particulates in the atmosphere can cause complications. The timing couldn’t be much worse, considering that a recent Harvard study shows that long-term exposure to fine particles of pollution in the air, much like dust, may be linked to higher rates of hospitalization and death due to COVID-19.

Currently the dust is thickest from Texas to Florida.

If you are having trouble depicting the #dust among the clouds, I drew a approx outline around it. The dust is the milky hazy gray among the brighter white clouds. #DustStorm #dustcloud pic.twitter.com/CkKmW5fjNu

— Jeff Berardelli (@WeatherProf) June 26, 2020

The dust is responsible for the dense haze shrouding Houston’s skyline in the photo below.

Texas Daily Life
Downtown Houston is cloaked in haze as a Saharan dust cloud moves over parts of Texas on Friday, June 26, 2020.

David J. Phillip / AP


Most of the dust layer exists far above the surface — mostly between a few thousand feet above the surface to about 15,000 to 20,000 feet up. However, vertical mixing of the atmosphere and rainfall can bring that dust to the ground, and that’s when it can become harmful to people with respiratory issues.

In some places, like the Southeast, enough dust will settle that odds are people there will be able to see a thin layer of dust on their cars.

Dust watch day 2. Some low clouds moving through then the gray haze of the dust up top. Just too dense for nice sunrise colors. Air quality alert today. #Nola #dust #SaharanDust pic.twitter.com/XnHQIX9qrh

— Hank Allen (@HankAllenWX) June 26, 2020

SAHARAN DUST! ☀️🐪

A pilot and @WINKNews viewer sent me this earlier today above Florida at 15,000 ft. Wow! @StormHour @spann @JimCantore pic.twitter.com/wNRoZLLmQm

— Matt Devitt (@MattDevittWINK) June 26, 2020

Brown Haze can be seen in the Sky over Corpus Christi this morning indicating the Saharan Dust has arrived. #stxwx pic.twitter.com/aigikxVeQJ

— NWS Corpus Christi (@NWSCorpus) June 26, 2020

2pm update: this isn’t going to go over well 😆 pic.twitter.com/Da5xSqzGhM

— Patrick Ryan (@pmcelligott) June 25, 2020

The dust plume is forecast to break into two chunks due to a split in steering flow in the mid levels of the atmosphere, which will act as a guide. 

One part of the dust cloud will be pulled northward from Texas through the Plains States and Midwest this weekend, and even to the Canadian border on Monday morning. The dust will diffuse and thin out dramatically by the time it reaches the nation’s middle, but cities like Kansas City, Minneapolis and Chicago will see a hazier than normal sky. The dust in the atmosphere will also make for some especially vivid sunrises and sunsets.

The other batch of dust will be thicker and linger in the South, impacting Texas and areas eastward and northeastward into the Tennessee Valley, the Carolinas and Florida. Here the dust will be thick enough to pose breathing risks. It is recommended that people in these areas wear a mask when outdoors.

This NASA animation below shows the progression of the dust through Sunday. The white areas are where dust will be the most dense; the blues and purples show where it will be more diffuse. 

The latest Saharan Dust Layer forecast keeps most of the dust in the SE 1/4 of the nation… but some of the thinner haze will float north through the Plain states, Midwest, Ohio and TN Valley – even areas like Missouri, Iowa, Chicago will see some dust by Sunday – albeit thin. pic.twitter.com/GWwcyUIlYX

— Jeff Berardelli (@WeatherProf) June 26, 2020

Now, dust has both negative and positive impacts. 

On the positive side, for millions of years dust has been transported by the east-to-west trade winds from Africa across the Caribbean to Florida, supplying much of the soil, and nutrients in the soil, for growth of vegetation. Scientists believe that the nutrient load in the environment around Florida and the Bahamas is otherwise so poor that without the African dust, the coral reefs would have had a hard time growing and flourishing. Dust plumes also supply much of the nutrients to sustain life in the Amazon rainforest.


NASA | Satellite Tracks Saharan Dust to Amazon in 3-D by
NASA Goddard on
YouTube

Naturally, due to the severity of this dust cloud, many are wondering if it has any connection to climate change. The evidence is mixed. As to whether this dramatic dust cloud was made worse by climate change, there is no clear answer yet. But the process of dust cloud formation can lend some clues.

Dust forms in the Sahara desert and on the edge of the more lush Sahel — a narrow transition zone between desert to the north and savanna to the south — in north Africa. There is evidence that these areas have been generally drying out and the desert has been expanding lately due partially to natural cycles and partially to human-caused climate change. 

As the Earth warms, evaporation of surface water increases, drying out the Sahara and the northern fringe of the Sahel even more. A 2019 study did indeed find that dust transport increased in the last century compared to the last 2,000 years.

In the future, the climate models project mixed results in terms of decreased rainfall and increased heavy rain events in the area due to climate change. However, it seems virtually certain that even if there is more rain, it will not be enough to counteract the increased evaporation. Thus, the Sahara and Sahel will likely dry out even more. This would theoretically create more dust.

But, on the other hand, a study in 2016 found that the bigger controlling factor for dust clouds may be potential changes in the wind flow. In this case, the study finds in the future the tropical circulation may weaken due to global warming. Weaker winds would stir up less dust from Africa and thus dust clouds in the Atlantic would decrease. 

Decreased dust in the tropical Atlantic may mean a warmer ocean, due to less dust blocking the sun. And less dry-dusty air could mean a better chance for hurricanes to form and intensify. But the jury is still out on that. 

What is clear is that the atmospheric dust plays an important role in our lives, affecting everything from respiratory health to pretty sunsets, and from fertilizing coral reefs and forests to squelching hurricanes. Positive or negative, what this dust cloud episode teaches us, once again, is that everything on Earth is interconnected.

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Historic Saharan

The historic Saharan dust plume is darkening skies in the Caribbean and will soon stretch into the US – CNN

(CNN)The current Saharan dust episode is leading to the worst dust storm in the Caribbean in decades.

Over the weekend, Saharan dust moved into the Caribbean. By Monday, it had changed the tropical blue skies into a hazy brown-gray color.
On Tuesday, this sunset enhancing, blue sky limiting, tropical threat reducing dust plume continues its 5,000-mile journey toward the US.
But before it does, it is leaving these pristine islands with a few more days with one the most significant dust events seen in the Caribbean.
“It is definitely historic,” Olga Mayol-Bracero, a researcher at the University of Puerto Rico told CNN Weather. “We knew we were going to be in an extraordinary situation.”
Many of her colleagues across the Caribbean said they have not seen air quality conditions this bad in their entire careers.
Aerosols, measured in PM10, at Mayol-Bracero’s research station in northeastern Puerto Rico, have never reached the levels they have seen the past few days. Records at this station go back 15 years.
It is unusual that the dust is forecast to travel over central America and the US with such high concentrations, Claire Ryder, NERC Independent Research Fellow at the University of Reading, told CNN Weather.
“Usually by the time dust from the Sahara has traveled this far, much of it has been dispersed and/or deposited to the ocean so that typically this long-range transport to the Americas would involve much lower concentrations,” Ryder said.
The initial dust outbreak was driven by a few different smaller storm systems over central and west Africa. Several of these thunderstorms caused downdrafts and large-scale haboobs (dust storms) to develop. This led to a large amount of dust being uplifted into the atmosphere from the Sahara, according to Ryder.
At the same time, these smaller dust storms were happening. The African Easterly Jet, strong winds higher in the atmosphere which usually transports dust westwards, was anomalously weak this June.
Meaning a larger amount of dust than usual was able to accumulate just off the west coast of Africa. It was able to then was transported westwards in a very dense plume when the jet picked up speed again.
This increase in dust thickness has led to the dirty looking skies seen across the Caribbean and the historically poor air quality.
“It’s certainly the most intense, large-scale dust event I have ever seen,” Ryder said.
The dust layer is so thick you can see it on weather satellites. Astronauts have also gotten a good view of it from the international space station.
“We flew over this Saharan dust plume today in the west central Atlantic,’ Astronaut Doug Hurly tweeted on Sunday. “Amazing how large an area it covers!”
“Hazy skies and low visibilities will continue today as a significant Saharan dust event continues across the islands,” the National Weather Service in San Juan said Tuesday morning.

The Saharan dust will reach the US by Thursday morning

On Wednesday, the dust is forecast to move across the Gulf of Mexico toward Texas.
Thursday morning, people in places like Brownsville in Texas and Houston will likely wake up to a beautiful sunrise and a hazier than normal sky.
Forecast models don’t show the thicker concentration blanketing most of Central America and Mexico Thursday.
This thicker layer is likely to reach Texas by Friday and then take a turn to the east. If the forecast model is right, it will move over most of the Southeast and MidAtlantic states over the weekend.
Once it arrives, here are the top 3 ways you’ll notice next week’s Saharan dust in the US, wrote CNN meteorologist Tyler Mauldin.

A difference in the sky

One of the first things you’ll notice when the Saharan dust layer arrives is that your typical blue sky will have more of a milky haze to it.
That milky haze is the Saharan dust. Those tiny dust particles lofted tens of thousands of feet in the air do a great job of scattering the sun’s rays at dusk and dawn, too, which gives way to stunning sunrises and sunsets.
So, grab those cameras!

Less tropical activity in the Atlantic

The Saharan dust to a hurricane is nothing more than extremely dry air. Hurricanes hate dry air. A hurricane needs a hot, humid and calm environment.
As long as the Saharan dust is around … it’s likely you’ll see the National Hurricane Center watching fewer areas in the tropics.

Dust plume allergies

The tiny dust particles that give way to beautiful sunrises and sunsets and help suppress hurricane development don’t always stay at 30,000 feet. Sometimes particles can make their way to the surface, greatly affecting those with sensitive allergies.
If you find yourself reaching for a tissue this week — or your iPhone to post yet another awesome sunset pic to Instagram — thank the Saharan dust.

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