Western Europe and the Canary Islands have been coated with an inordinate amount of Saharan dust this spring. And though the dust is considered a hindrance, if things go just right, the rust-colored plumes may swing toward the U.S. and help dampen hurricanes during the upcoming “extremely active” hurricane season.
In a release, scientist Mark Parrington of the European Union’s Copernicus Atmosphere Monitoring Service said, “There has been an increase in the intensity and frequency of such episodes in recent years, which could be potentially attributed to changes in atmospheric circulation patterns.”
Saharan dust, and the extremely dry air that carries it, can be a hurricane killer. But will the current dust-up over Europe translate to that dry air choking out tropical systems over the Atlantic this summer?
Dust in the wind!
Yesterday, the #Meteosat10 satellite, operated by our European partners @EUMETSAT, caught this imagery of Saharan dust blowing over the Canary Islands. pic.twitter.com/9ObmJs5Tsg— NOAA Satellites (@NOAASatellites) April 12, 2024
It’s hard to say.
“What’s going on now in Europe — there’s no correlation one way or the other as to whether that will foretell any pattern for the summer,” said Robert Molleda, the warning coordination meteorologist at the National Weather Service’s Miami office. “These patterns can change pretty quickly. … We’re also going through a transition period between El Niño and La Niña, so weather patterns are ill-defined.”
But, if the dust does swing our way, it could help dampen storm formation — which would be good news in a season that experts think will be “very active” due to extremely high water temperatures in the Atlantic basin.
“When you have Saharan dust over parts of the Atlantic, that’s also a reflection of dry air in the middle levels of the troposphere, about 10,000 feet above the surface,” Molleda said.
“Hurricanes and tropical systems require adequate moisture for cloud formation, which is what helps to provide the energy for these storms to form. If you have a layer of dry warm air, that can limit potential tropical storms from forming or intensifying.”
The dry air can kneecap storms in another way, too.
The National Oceanic and Atmospheric Administration said that the Saharan air layer that carries the dust is traveling at a brisk 25 to 55 mph — fast enough for its wind shear to knock a storm off balance.
The dry blast “can cause tilting of the tropical cyclone vortex with height and can weaken the storm’s internal heat engine,” said NOAA.
It’s not a guarantee, said Molleda, but the fast-moving dry air can certainly inhibit storms.
The most significant factor in the dry dust’s impact, he said, are the forces that steer it.
The dry wind’s travel is influenced by the position of the Atlantic Subtropical High, a semi-permanent high pressure system that swells in size and shifts around over the ocean.
It’s divided into two hubs, the Bermuda High and the Azores High.
When it shifts east toward Africa, Saharan dust will first travel along its southern edge, but then cut north once it rounds the end of the high. That keeps the dust away from Florida.
When Atlantic Subtropical High shifts west toward the U.S., it allows winds from Africa carrying dust to spread over the Atlantic and reach Florida. This would keep the dry air in the hurricane Main Development Region, from the coast of Africa to the Caribbean, longer.
A western leaning high is a double-edged sword, though.
Yes, it allows dry air to reach Florida, but it also steers tropical systems toward Florida or the Gulf of Mexico. Tropical cyclones want to spin north, but the high pressure blocks their path, and they keep moving west, toward the U.S.
And at this point, it’s too early to tell what the subtropical high will do this summer, Molleda said. And much too early to tell how many surges of dust will rise off the Sahara.
The pending La Niña
A big story this year is the transition from El Niño, which tends to dampen hurricane season with wind shear, and La Niña, which tends to have less shear, and therefore benefit storm formation over the Atlantic.
“I have not been able to find any direct notable correlation between La Niña and the extent of Saharan dust,” Molleda said.
At the moment, El Niño still exists, but the eastern Pacific is cooling, which will likely lead to a La Niña.
A fringe benefit of Saharan dust reaching Florida — resplendent orange and red sunsets.
