Varying Saharan Dust Concentrations To Linger Over Next 10 Days

A significant surge of Saharan Dust moved across the Lesser Antilles over the past weekend, with higher concentrations remaining north of Trinidad and Tobago.

Peak concentrations occurred early Sunday, October 3rd, 2021 with visibility reducing to 3 kilometers across Trinidad and 9 kilometers across Tobago. Similarly, islands north of T&T experienced reduced visibility. In Barbados, visibility was reduced to 8 kilometers, 4 kilometers in St. Vincent and the Grenadines, and 8 kilometers in Grenada.

Through the next 10 days, fluctuating mild to moderate concentrations of Saharan Dust are forecast to move across Trinidad and Tobago with higher concentrations remaining north of the country.

Over the last 24 hours, air quality has been good to moderate 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

Over the next 10 days, tropical cyclone activity east of the Lesser Antilles is forecast to be minimal with tropical waves and troughs providing Saharan Dust relief across the region.

Across Trinidad and Tobago, the Intertropical Convergence Zone (ITCZ) will linger near the country, shielding the islands from higher dust concentrations.

Model guidance suggests a mild to moderate ongoing surge is forecast to lessen across T&T through Thursday 7th October 2021. Rainfall associated with the ITCZ and Tropical Waves is forecast to lessen the air quality impacts of lingering Saharan Dust from Thursday through next week.

Generally, air quality levels are forecast to remain good levels, only becoming moderate during high-traffic periods as well as across Tobago where rainfall will be less than across Trinidad. Outside of rainfall, visibility is forecast to remain at or above 10 kilometers.

00Z October 4th 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
00Z October 4th, 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.

What does this mean for you?

Over the next 10 days, air quality is forecast to remain at mostly good levels. However, during high traffic periods, particularly between 6:00 AM and 9:00 AM, and again during 3:00 PM through 6:30 PM, air quality may dip to moderate levels in localized areas. Also, across Tobago and at times Northern Trinidad, air quality may dip to moderate levels.

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 during these high traffic periods.

We’re in a period where the ITCZ, tropical cyclones, 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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