A large plume of Saharan dust emerged off the coast of western Africa this week and has now reached the Caribbean Sea and South America. This is the season’s first large plume of Saharan dust to cross the Atlantic.
The plume is expected to reach the U.S. Gulf Coast over the weekend.
This mass of very dry, dusty air is called the Saharan Air Layer (SAL). It typically ramps in mid-June and subsides after mid-August.
SAL can suppress clouds and thunderstorms when it reaches the U.S. coastline.1
Some areas will experience their hottest days of the summer when the SAL’s dry, dusty air is overhead and afternoon thunderstorms are being stifled.
Because of the special way Saharan dust scatters sunlight, the best times of day to spot it are usually a few hours after sunrise and in the late afternoon. During the day, the sky will have a hazy white look and sunsets will take on an orange glow.
The Saharan Air Layer has unique properties of warmth, dry air, and strong winds that can have significant moderating impacts on tropical cyclone formation and intensification.
There are three characteristics of these Saharan dust outbreaks that can affect tropical cyclones, tropical disturbances, and the general climatology of the Atlantic tropical atmosphere: extremely dry air – which can weaken a tropical cyclone or tropical disturbance by promoting downdrafts around the storm, African Easterly Jet – which can cause tilting of the tropical cyclone vortex with height and can disrupt the storm’s internal heat engine, and warm temperatures which stabilize the atmosphere and can suppress the formation of clouds.
1 The Saharan Air Layer and Extreme Weather – NOAA
Featured image credit: NOAA/GOES-East, Zoom Earth, The Watchers
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