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Thursday, June 25, 2020

Saharan dust to visit the Mid-South

The next in a string of unusual events in 2020 may be the arrival of Saharan dust in the United States, and more specifically, the southeast U.S. and Mid-South!

Before you start fearing the worst... though this seems to be a fairly noteworthy event as Saharan dust storms go, it actually is likely to have minimal harmful effects on Mid-South weather for the majority of people. But it could indeed be noticeable if you are paying attention!

Background

Saharan dust storms (or more accurately, the "Saharan Air Layer [SAL]") are not uncommon and occur every year, mainly in the summer months, when large storms that generate a great deal of wind in the equatorial regions of Africa pick up dust from the Sahara desert and spew it into the atmosphere. The easterly trade wind then transports that dust over the Atlantic Ocean and westward. It is not uncommon either for dust to make it as far as the Caribbean and more tropical regions of the U.S. (think Florida for example). What makes this storm different seems to be its intensity - the amount of dust it contains and the lengthy path it is taking, following the prevailing wind right into the southeast U.S., with enough dust still suspended to be noticeable.

The image below was taken by one of the astronauts that just rode the SpaceX vehicle to the International Space Station a couple of weeks ago, showing the extent of the dust coverage over the central Atlantic.



Forecast

The current dust cloud has moved across the Atlantic and is arriving in the far southeastern U.S. now. The forecast loop below shows the path the dust is likely to take over the coming days, specifically from Thursday evening through Saturday evening. We could see some of the dust over the Mid-South Friday and Saturday.


While we aren't likely to see as poor of conditions as were observed in San Juan, Puerto Rico a couple of days ago, here's what was observed there this week:



Effects of the SAL

As you can see from the image above, the density of the dust in the Caribbean was quite high. However, after a couple thousand more miles of travel, it isn't likely to be as noticeable to the naked eye here. That doesn't mean it won't be noticed at all though! The most common effects of Saharan dust in the sky are:

  • More brilliant sunrises/sunsets - particularly in the orange/red realm if dust remains suspended high in the atmosphere
  • Hazy sky - if the dust settles out a bit lower, than our typical blue skies may be more muted or even a bit "hazy" with a tinge of brown.
  • Higher air pollution levels - especially if you notice a haze in the sky that seems to start near the ground. This would indicate that the dust is more prevalent in our little section of the atmosphere (the lowest 6 or so feet), which could be a mild irritant to those who suffer from allergies, asthma, or other breathing difficulties. Keep this in mind if it appears hazy out and take precautions if you are in a sensitive group.
  • Reduced visibility - in the most severe cases, and not likely here in the Mid-South, visibility can be reduced, almost like a smog scenario
  • Suppression of tropical activity - one of the side effects of Saharan dust is it also suppresses tropical storm formation in the Atlantic as the atmosphere is filled with a drying agent that keeps these systems from tapping into the moisture necessary to survive, as well as reflecting heat back into the atmosphere.

So be on the lookout (when it is not cloudy or raining) the next couple of days for signs of the Saharan dust!



Erik Proseus
MWN Meteorologist

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