True color visible satellite image of the Atlantic Ocean (above) from June 23, 2020. Courtesy College of DuPage
It’s been making weather news frequently to end June; an outbreak of African dust, or a “Saharan Air Layer” working across the Atlantic and into the Caribbean. The above satellite image shows the dust, marked by a brownish, reddish hue; one across the Caribbean, and another coming off of Africa into the eastern Atlantic.
I have a buddy living in St. Croix. Saharan dust is in full effect pic.twitter.com/fEDy1JL6Qh— Tyler Castillo (@tjc_12) June 22, 2020
Saharan dust outbreaks are not a new thing, they happen every summer as east-west tradewinds blow off the higher elevations in parts of northern Africa, and bring the hot, dry and dusty air with them. However, this current outbreak is much more significant than normal, with the dust leaving deposits on objects, harming air quality, reducing visibility, and partially blocking out the sun across the Caribbean. While the dust itself has some limited impact on the weather (it blocks sun from reaching the surface and modestly warms the mid-levels of the atmosphere, having a stabilization effect), the source of the dust (the Saharan desert in northern Africa) is traditionally very hot and dry; this hot, dry airmass accompanies the dust and suppresses thunderstorm development. Note the pronounced lack of clouds on the satellite image above compared to surrounding areas.
Saharan dust outbreaks (and the hot, dry airmass that accompanies them) can hinder tropical development across the Atlantic. The amount and location of Saharan air can vary on timescales of days to a week or two, so it’s much to early for the late June outbreak of dust to have any sort of impact on peak hurricane season later in the summer.