Each year, more than a hundred million tons of mineral dust from the world’s largest hot desert are heaved across the Atlantic, often blowing through the Caribbean to the shores of South Florida, stifling our afternoon thunderstorms and making for hazy days and brilliant sunsets.
These Saharan dust outbreaks usually peak in June and July, and their timing can both thwart would-be hurricanes and cool down Atlantic waters.
But in 2023, with some exception, the sands of Africa were left largely undisturbed.
Overall, the concentration of dust over the tropical Atlantic in 2023 was the lowest since satellites began measuring the tiny, suspended particulate back in 2002.
How does the amount of dust affect hurricanes?
The amount of dust cover in the Atlantic picks up in earnest in June and usually peaks by late June or early July before falling off quickly in August as hurricane season starts to crank up. Since almost 90% of tropical activity doesn’t typically occur until after mid-August, the amount of dust doesn’t generally affect overall hurricane activity.
That said, episodic dust outbreaks still happen in August and September and a well-timed dust plume can help to weaken developing storms, both by increasing wind shear on the edge of the dust plume and putting the lid on growing thunderstorms.
Dust is also a very effective sink for sunlight, trapping the heat that might otherwise reach the Earth’s surface. So lots of dust cover over the Atlantic can help to cool down the ocean during the summer months. When the dust doesn’t show, especially during the peak summer months like in 2023, the ocean’s surface can heat up more quickly. Although not the primary factor modulating Atlantic sea surface temperatures, studies find dust cover (or lack thereof) explains a significant 35% of the June to August water temperature variability. Though the paltry dust plumes probably didn’t cause the record-breaking Atlantic warmth in 2023, it certainly didn’t help matters.
What about Saharan dust across the Atlantic so far in 2024?
So far things have been fairly normal in the dust department. Overall levels of dust are running about average, but we haven’t had a significant dust outbreak since mid-April and we also haven’t hit the dustiest part of the year.
We’ll be watching carefully for those dust outbreaks to help cool down an exceptionally hot Atlantic and perhaps stave off a storm or two in what’s forecast to be a very active hurricane season.
What’s ahead in the tropics (buyer beware on the GFS)
As we’ve discussed in newsletters this week, the tropical Atlantic should stay quiet into early next week. The NHC is not anticipating any development over the next 7 days.
By mid next week, the tropical tap will turn on and may bring a dose of beneficial rains to South Florida, where we’ve largely been running a deficit this spring. Of course, too much of a good thing in too short a timeframe is a bad thing, so we’ll keep an eye on the rainfall trends for next week.
For now, tropical development is unlikely next week.
(The American GFS model is characteristically bullish on spinning up a tropical system in the Gulf by late next week. It originates from unrealistic amounts of spin near northern South America streaming into a broader area of low pressure situated over Central America. This is a known bias of the GFS at longer lead times and the solution of a tropical system in the Gulf next week isn’t supported by other reliable models or by the overall environment. Buyer beware for now.)
