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Answering your questions about Saharan dust

The annual irritant may have you scratching your head

Dust as seen on NOAA satellites, valid Sunday, June 28, 2020
Dust as seen on NOAA satellites, valid Sunday, June 28, 2020 (KSAT 12)

Saharan dust has made for a hazy few days in San Antonio. The dust was at its most dense on Saturday, June 27, 2020. That’s when the San Antonio skyline was nearly impossible to see from a distance and air quality was considered “unhealthy” for everyone.

Sky Conditions and Air Quality in San Antonio on Saturday, June 27, 2020
Sky Conditions and Air Quality in San Antonio on Saturday, June 27, 2020 (KSAT 12)

Thankfully, the dust began to thin out on Sunday, June 28th. It wasn’t as hazy outside, and air quality improved.

Sky Conditions and Air Quality in San Antonio on Sunday, June 28, 2020
Sky Conditions and Air Quality in San Antonio on Sunday, June 28, 2020 (KSAT 12)

While Saharan dust’s arrival in Texas is an annual event, it has gotten a lot of additional attention this year amid the COVID-19 pandemic. That’s led some KSAT viewers to send questions about the dust to the Weather Authority team.

Question 1: How does the dust make it all the way across the Atlantic Ocean to Texas without falling to the ground first?

Answer: The dust originates in the Saharan Desert region of Africa. This dust is lofted into the air there, and is picked up by the trade winds that move from east to west near the equator in the Northern Hemisphere. Since the trade winds are permanent, they’re always there. This means there is always a conveyor belt - if you will - present to move the dust across the Atlantic Ocean. You can almost think of it like an endless game of hot potato: the dust never gets dropped!

Trade winds near the equator pick up Saharan dust and carry it over the ocean.
Trade winds near the equator pick up Saharan dust and carry it over the ocean. (KSAT 12)

Question 2: Why doesn’t Saharan dust get all over everything like the dust from storms in West Texas?

Answer: Saharan dust and the dust storms in West Texas happen in two completely different ways and are from two completely different sources. As previously mentioned, the Saharan dust is carried over from Africa and happens on a pretty large scale. We’re talking dust plumes thousands of miles long that can affect multiple states at a time!

West Texas dust storms are also known as haboobs. Haboobs form when a nearby thunderstorm produces an outflow. Outflows produce strong winds that pick up loose sediment, like dust and clay, and form a large, moving cloud of dust. These dust clouds are called habobs. A haboob can be quite large, but can usually be compared to the size of a supercell thunderstorm (about 10 to 15 miles in length). The dust that is carried in a hoboob is also moving at the surface of the Earth, which means it can leave a red-ish layer of dirt behind on vehicles, buildings...pretty much anything. In contrast, Saharan dust can be concentrated up to a mile or so up in the sky, meaning the particulates are ‘spread out’ a bit more. This generally keeps noticeable amounts of it from being left on surfaces. (The exception to this is when it rains and Saharan dust is present. In that case, you may be left with a muddy residue on your car!)

Question 3: When will it go away?!

Answer: This is a valid question, since Saharan dust can be irritating to some South Texans! As of Sunday, June 28, 2020, Saharan dust is expected to become dense over San Antonio again by Thursday, July 2, 2020. However, the dust can filter in and out of our skies for weeks at a time, with some days being worse than others. Your Weather Authority team provides updates on the dust whenever it’s around, and you can find the latest on the weather page.

Check out photos of the dust from around South Texas:

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