Hurricanes and dust in the wind

After 3 early hurricanes, the first few weeks of the season have been quiet.

This image from NOAA may show why, there is an unusually massive dust plume reaching into the western parts of the Caribbean which is expected to be visible to the US Gulf States from today. These plumes of dry Saharan dust, termed Saharan Air layer (SAL) by meteorologists, are whipped up by winds linked to a strong mid level African Easterly jet during the late Spring, Summer and early Autumn and transport some 50,000 tons of sand annually across the Atlantic. The SAL is typically located between 5000 and 20000 feet with activity peaking in June, and can occasionally reach as far west as Texas which is an impressive 5500-6000nm from the main central Sahara source. This current dust cloud has been monitored by NASA since 13 June and is still going strong 10 days later.

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There is good and bad news for the mariner. 

The good news is that the dry air and strong winds are thought to suppress tropical cyclone formation in the Atlantic, as they need warm, humid air and light winds to grow and intensify. A SAL has typically about 50% less humidity and the strong winds in the plume (from the Easterly jet) increase the wind shear so suppressing any potential to grow thunderstorms. If you look at the dust, you can see the effect it has on the convection below and the general lack of heavy shower clouds. The result is that the Atlantic is likely to remain quiet over the next week or so. The bad news comes in two parts, firstly the visibility immediately off the African coast will be poor reducing to fog limits at times in the thicker plumes (this webcam from the Cape Verde Islands shows next to no visibility 22 Jun 1454UTC https://www.webcamtaxi.com/en/cape-verde/sal/kite-beach.html) and secondly the airborne particulates can be irritating for those with allergies and respiratory conditions, plus research has shown that these dust plumes carry other pathogenic bacteria.    

This article was originally posted on LinkedIn.

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