Saharan Dust Surge Expected By Mid-Week

A trio of tropical waves and another trio of tropical disturbances in the Atlantic is keeping dense concentrations of Saharan Dust north of the Lesser Antilles. However, by mid-week, a brief but moderate surge of dust is forecast to move across Trinidad and Tobago, with another surge expected by the end of the upcoming weekend.

Over the last 24 hours, air quality has been good to moderate with visibility outside of showers and thunderstorms near and above 10 kilometers across Trinidad and Tobago. The Environmental Management Agency (EMA) air quality monitoring stations are recording AQI values at levels that are good across the country. These measurements are based on PM2.5 (particulates the size of 2.5 micrometers and smaller, usually associated with increases in Saharan Dust, vehicle exhaust, and smoke) and PM10 particulates.

The Saharan Dust Forecast

Air quality across the country is forecast to remain at good levels through the next 48 hours, at least through the overnight hours of Tuesday. The passage of Tropical Wave 30 overnight Saturday into Sunday, the expected passage of Invest 94L, and Tropical Wave 31 on Monday and Tuesday respectively are all forecast to shield T&T from Saharan Dust.

Following the passage of Tropical Wave 31, a surge of Saharan Dust is forecast to follow, moving across the region. This surge is forecast to be short-lived, as improvement is expected by Friday, as Tropical Wave 32 moves across the Lesser Antilles.

Then, another brief surge moves in on Sunday, ahead of Tropical Wave 33 (yet to move into the Atlantic) moves across the region, improving air quality again.

Like clockwork, another surge of dust will arrive again mid-week the following week.

Air quality levels will fluctuate between good to moderate through the entire forecast period. On days with peak concentrations, visibility may be reduced between 7-10 kilometers.

00Z 8th August 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.

What does this mean for you?

For the general population, with moderate Saharan dust concentrations forecast, little to no impacts are forecast beyond hazy skies. For sensitive groups, such as children, the elderly, and persons who suffer from respiratory ailments and allergies, you may need to avoid prolonged exertion outdoors on days with high concentrations of Saharan Dust.

We’re in a period where the ITCZ and tropical waves may shield Trinidad and Tobago from significant dust events. While tropical waves play a notable role in moving dust across the Atlantic and the Eastern Caribbean, these periodic tropical waves also improve air quality.

The concentration of the dust that follows the wave depends on the strength of the wave as it moves off the West African Coast. This is because of stronger thunderstorms across Central Africa. As strong winds move downward and outward from these thunderstorms, the wind kicks up dust as it moves across parts of the Saharan Desert and transports it into the upper atmosphere. This “plume” of dust follows the axis of the wave as it progresses westward into the Atlantic.

Dust that makes it into the upper levels of the atmosphere can then get transported across the Atlantic Ocean. The plumes of dust eventually affect the Eastern Caribbean.

Larger, more concentrated plumes of dust begin to occur in April and continue through November.

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