Saharan Dust To Move Across Lesser Antilles Through The Next Few Days

A surge of Saharan Dust is set to move across Trinidad, Tobago, and the remainder of the Lesser Antilles beginning on Thursday.

Higher concentrations of Saharan Dust are forecast to remain north of the country, with activity associated with Tropical Wave 58 and 59, as well as the Intertropical Convergence Zone improving air quality across T&T.

While moderate to high concentrations are forecast through the next 48 hours, from Saturday, fluctuating mild to moderate concentrations of Saharan Dust are forecast to move across Trinidad and Tobago with higher concentrations remaining north of the country.

It should also be noted that for islands north of Trinidad and Tobago, mainly across the Leewards and the Greater Antilles, sulphur dioxide from the Cumbre Vieja Volcano on La Palma, Canary Islands, is forecast to move across the region at high altitudes. It poses no threat to those on the ground. The only reason it is being mentioned is it may be picked up on social media and could be misconstrued to appear as it could become harmful.

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

00Z October 20th, 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Sulphates Aerosol Optical Total showing Sulphates.
00Z October 20th, 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Sulphates Aerosol Optical Total showing Sulphates.

A surge of dust is moving across the Lesser Antilles as early as Wednesday night and this high-concentration surge is forecast to linger through the end of the week across the region.

For Trinidad and Tobago, concentrations are forecast to diminish through the weekend and into next week as an active tropical wave (Tropical Wave 59) and the Intertropical Convergence Zone moves over and remains across the country.

Dust concentrations are forecast to remain mild to moderate from Monday through the upcoming week.

Further north, fluctuating concentrations of dust and high-altitude sulphur dioxide and sulphates are forecast to move across those areas over the next 10 days. Note that sulphur dioxide and sulphates will not impact air quality near the ground. As mentioned earlier, these gases pose no threat to those on the ground.

Generally, air quality levels are forecast to remain good levels, only becoming moderate on Thursday and Friday, as well as during high-traffic periods. Outside of rainfall and peak dust days, visibility is forecast to remain at or above 10 kilometers.

00Z October 20th, 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.
00Z October 20th, 2021, NASA GEOS-5 Dust Extinction Model Monitoring Tropical Atlantic Dust Aerosol Optical Depth showing Saharan Dust.

What does this mean for you?

On Thursday and Friday, air quality is forecast to be near moderate levels across Trinidad and Tobago. From Saturday and through much of next week, 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.

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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