Saharan Dust Sticks Around. Still, Tropical Waves To Improve Air Quality This Weekend

High concentrations of Saharan Dust have persisted across T&T for the last three to four days. Over the several days, two tropical waves are forecast to move across the region, bringing some brief dust relief before another Saharan Dust surge arrives on Monday.

Over the last 24 hours, air quality has been good to moderate with visibility outside of showers and thunderstorms between 6 to 10 kilometers across T&T. The Environmental Management Agency (EMA) air quality monitoring stations are recording AQI values at levels that are good in Trinidad and Tobago. 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

Through tonight and into the first half of tomorrow, high Saharan Dust concentrations are forecast to gradually decrease as Tropical Wave 23 (renamed as a new wave was analyzed moving across the Lesser Antilles on Wednesday) nears the region.

Moderate concentrations will linger across the Lesser Antilles as this wave moves westward, with a significant surge of dust traversing the Eastern Caribbean on Friday, though higher concentrations will remain north of T&T.

As Tropical Wave 24 nears and moves across the region Saturday into Sunday, little to no dust is forecast across T&T, with improvements in air quality and visibility. However, this improvement will be short-lived as another surge of dust arrives on Monday and lingers into next 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 6-10 kilometers.

12Z 21st July 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 to high 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.

For countries in the Leewards, air quality could dip to levels that are unhealthy for sensitive groups.

With high concentrations of Saharan Dust forecast, members of sensitive groups may experience health effects. The general public is not likely to be affected though visibility will be reduced due to increased 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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