Dust from the Sahara Desert on the way to the Deep South

MONTGOMERY, Ala. (WSFA) - It’s that time of year again! Dust all the way from the Sahara Desert in Africa is eyeing the skies above the Atlantic, Caribbean, Gulf of Mexico, and Southeast U.S.

That includes Alabama, which is more than 6,000 miles from the Sahara Desert!

It will push into the Gulf of Mexico Friday night and eventually reach Texas, Louisiana, Mississippi, Alabama, Georgia, and Florida this weekend. For us in Alabama it will be present over the weekend and early next week in varying levels of concentration. This plume won’t be overly thick for us, but we will likely be able to notice it in our skies.

It may seem impossible for dust to travel from Africa to the United States, but it is a normal yearly phenomenon. Plumes of dust continuously push westward off the coast of Africa during the months of June, July and August. It can happen as early as May some years if conditions are right.

This happens as tropical waves and their corresponding stronger winds over Central Africa loft vast amounts of dust into the atmosphere. The Saharan Air Layer (SAL) then pushes across the Atlantic Ocean courtesy of easterly winds.

Each plume of dust differs in size, thickness and concentration, but we usually see dust outbreaks push off the African coast every 3-5 days during the mid-June to mid-August period. The dust outbreaks typically occupy a 2 to 2.5-mile thick layer of the atmosphere beginning just over a mile off the surface, according to NOAA.

The heavier and larger plumes of dust oftentimes make it all the way to the Caribbean, Gulf of Mexico, Florida, and other southern states, but the extent of their impacts differs.

We can use forecast models to look at potential impacts by analyzing dust particle concentrations in the atmosphere and where outbreaks of that dust will likely move out to about 10 days. It’s important to know when and where the Saharan dust will go because it has multiple impacts -- both good and not so good.

If the dust concentration is thick enough, air quality problems and breathing/health issues can arise. That is especially true for those who suffer from respiratory problems. If the dust concentration is high enough, some folks may have to avoid outdoor exposure.

Rarely is the dust concentration high enough in Alabama to cause significant issues in terms of our air quality. Poor air quality is only one effect of these annual Saharan dust invasions.\

The dust is thought to help build beaches in the Caribbean and enrich soils and oceanic ecosystems courtesy of the minerals and nutrients it contains. Those ingredients aid in the fertilization of the Amazon Rainforest, especially the limited amounts of phosphorus. Some scientists suggest the iron in the dust may fertilize the ocean, feeding microorganisms in the water.

For us here in Alabama, the noticeable impacts of Saharan dust are particularly colorful sunrises and sunsets, a milky/hazy sky during the day and a suppression of tropical cyclone development in the Atlantic basin (including the Gulf of Mexico).

The hot, dusty SAL creates very dry conditions in the atmosphere. This is why tropical storm and hurricane development are heavily suppressed. Tropical systems need warm, moist air to form, strengthen and maintain themselves. With the hot, dry and dusty air in place, the Atlantic is typically on the quieter side in May, June and July.

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