Beginning on June 13, NASA-NOAA’s Suomi NPP satellite observed a huge Saharan dust plume streaming over the North Atlantic Ocean. Satellite data showed the dust had spread over 2,000 miles.
Further satellite imagery and modeling of the dust plume show the dust moving across the tropics – the main areas of tropical development – and into the Gulf of Mexico between Tuesday and Thursday next week. This means the dust cloud will have traveled over 5,000 miles.
“According to scientists … this is an abnormally large dust cloud,” says senior AccuWeather meteorologist Dan Kottlowski.
“One of the things I noticed from this is the dust started coming off the coast of Africa several days ago, in fact maybe over a week ago. And it’s still coming. It’s almost like a prolonged area of dust,” he added.
A somewhat regular annual event
The Sahara desert is a key source of dust storms, particularly in what is called the Bodélé Depression and an area covering the confluence of Mauritania, Mali, and Algeria. Dust traveling from the Sahara to the Gulf Coast is common during June, July, and sometimes into early August.
Saharan dust storms have increased approximately 10-fold during the half-century since the 1950s. Levels of Saharan dust coming off the east coast of Africa in June 2007 were five times those observed in June 2006 and were the highest observed since at least 1999, which may have cooled Atlantic waters enough to slightly reduce hurricane activity in late 2007, according to NASA.
Normally, though, hundreds of millions of tons of dust are picked up from the deserts of Africa and blown across the Atlantic Ocean each year. Besides the short-term negative effects on respiratory systems, especially those people with asthma and COPD, as well as the danger of keratoconjunctivitis sicca (“dry eyes”), the one good thing the dust storms do is replenish the sands on beaches in the Caribbean and fertilizes soils in the Amazon.
African dust storms and tropical cyclone formation
The dust coming off the coast of Africa is picked up by the Trade Winds and tossed higher up into the atmosphere, where it gets trapped as the wind makes it away across the Atlantic.
Kottlowski believes the huge plume of dust seen this year may have something to do with the African easterly jet stream being a bit stronger than normal. Though the dust is a visible indication there will be little to no tropical development, it isn’t the main reason why a tropical system will not form when it is present.
“The dust is the visible part of the reduced tropical development potential area,” explains CNN meteorologist Chad Myers. “It is the dry air and additional vertical wind shear along with the dust that are the driving factors in limiting tropical storm development.”
Readers have heard the term “vertical wind shear,” associated with hurricanes in the Atlantic. Vertical wind shear is the change of wind speed and direction with height. For a hurricane to form, it needs little to no wind shear and a very moist atmosphere.
So it is doubtful that we will be hearing about a fourth-named storm in the Atlantic hurricane season in the next week or so.. Instead, just enjoy the vibrant and spectacular sunrises and sunsets.
