Q&A of the Day – Saharan Dust’s Impact on Weather & Hurricane Season
Each day I feature a listener question sent by one of these methods.
Email: brianmudd@iheartmedia.com
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Today’s entry: Hi Brian, I really appreciate your continually superior, national quality daily show content and presentation. Saharan dust seems to be a significant weather modifier as regards hurricane formation, but you are the only one who mentions this routinely. Why?
Bottom Line: Your kind words are greatly appreciated, as is your note. This question I thought was on point as something somewhat remarkable has happened as we’ve entered the absolute peak week of hurricane season... In addition to a benign first half of hurricane season this year, the National Hurricane Center’s map is currently clear with the best possible message we can hope for during Hurricane season posted: Tropical cyclone activity is not expected during the next 7 days.
Notably, and on topic, not only has a steady flow of Saharan dust factored heavily into what hasn’t developed in the tropics to date, but it was also responsible over the weekend for ending the threat of a tropical disturbance crossing the mid-Atlantic that at its peak was given a 90% chance of development. That implies that even the National Hurricane Center was surprised by the impact of Saharan dust on the system. By the way, if you follow the Hurricane Center’s notes – this wasn’t referred to as Saharan dust, but rather as “dry air”. That’s also how it was commonly referred to by many meteorologists.
I can’t specifically speak to why many meteorologists don’t actively cover Saharan dust during hurricane season, however the reason I do daily in my Florida News that Impacts You updates, is due to what I uncovered in research a few years ago that I’ve spoken to on a handful of occasions over the prior few years. That includes most recently having discussed this on the onset of this year’s hurricane season in my story: The Relationship Between Saharan Dust and Hurricane Season. As I’ve noted...
At the forefront of active hurricane predictions has been the topic of climate change. And specifically warmer temperatures, and especially warmer oceans, resulting in increasingly active hurricane seasons. This is logical. It’s a fact that warmer waters are more conducive for tropical development – hence why hurricane season occurs when it does. But there’s a big ‘ole fly in the climate change = ever more hurricanes argument... It’s not analytical.
You might have noticed we seemingly have had more Saharan Dust clouds flying over South Florida in recent years. It’s not your imagination, we have. I had been researching this because my wife Ashley has asthma, and the increasing Saharan Dust activity has meant she’s had to change inhalers and use them more often.
The catalyst for my focus on Saharan dust during hurricane season began following a Harvard study in 2020 entitled Climate change affects Saharan dust storms. The lead line says it all: A new groundbreaking study shows that the warming planet will make dust storms more intense in the Mediterranean and the Atlantic. Now, without diving into all the specs of the study, the bottom line is this. The past few years we have seen a marked increase in Saharan Dust clouds and Harvard’s researchers offer extensive evidence that rising temperatures/climate change is behind it. Few things act as a greater hurricane repellant than massive dust clouds across the entire Atlantic.
The Saharan Air Layer, which generally moves between 5,000 and 15,000 feet above sea level, contains an average of 50% less moisture. 50% less moisture doesn’t necessarily line up with 50% less tropical development, it can be more complicated than that, but it certainly reduces whatever else would be when present. The other potential benefit of the dust is the ability to ever-so-slightly impact ocean temperatures. The dust reflects some sunlight and reflects small amounts of solar radiation which can lead to slightly cooler ocean temperatures than otherwise would be when the dust is present. Last year, there was another meaningful development on this topic.
A study entitled: Leading role of Saharan dust on tropical cyclone rain-fall in the Atlantic Basin was published in Science Advances and highlighted by Stanford University. Among the studied conclusions was this: Surprisingly, the leading factor controlling hurricane precipitation is not, as traditionally thought, sea surface temperature or humidity in the atmosphere. Instead, it's Sahara dust. Without getting in the weeds of the research, the main takeaways were these. Saharan dust has become the single biggest factor in whether tropical formation takes place and how much rain is concentrated in storms that do form.
So again, I can't speak about the underlying factors that commonly lead to others covering hurricane season to commonly omit the discussion of Saharan dust, but given it’s demonstrated omni-importance I believe it’s essential to provide a complete picture. Two final notes.
Saharan dust isn’t new; however, its impact is. Historically regular Saharan dust plumes have ended near the end of July or early August. It’s not a coincidence that the peak weeks of hurricane season historically are the final two of August and the first two of September. It’s long been that way because the one-two punch of ocean temps being at peak highs for the year, along with the end of Saharan dust typically opening the floodgates for what will be during that year’s season.
What’s been different about this year’s season thus far, in comparison to recent years, is that in addition to Saharan dust still being present in early September, the plumes have also been consistently making their way into the Gulf of America. As you’re likely well aware, while we’ve been fortunate not to be faced with direct landfalls on the Atlantic coast of Florida for many years now, the Gulf has been ground zero for landfalls. The dust continuing into the Gulf this year has proved to date to be key from having a repeat of what we’ve seen in recent years.
As always there are two sides to stories and one side to facts. Hope that’s helpful.